,,physics ,,t[]1 ,,smi?1 ,,turton1 ,,& ,,cope ,illu/ration3 7,see p4#dda7 ,,?ree-,,color ,,pr9t+ ,y4 ,yell[ impression2 negative made ?r\gh a blue-violet filt]4 ,r4 ,crimson impression2 negative made ?r\gh a gre5 filt]4 ,,ry4 ,crimson on yell[4 ,b4 ,blue impression2 negative made ?r\gh a r$ filt]4 ,,yrb4 ,yell[1 crimson1 & blue comb9$2 ! f9al product4 7,c\rtesy ( ,phototype ,engrav+ ,co41 ,philadelphia47 ,,physics ,,by ,,willis ,e4 ,,t[]1 ,m4 ,,sci4 7,univ4 ( ,ill9ois7 ,,head ,,( ,,! ,,dep>tm5t ,,( ,,physics1 ,,englewood ,,high ,,s*ool1 ,,*icago ,,*>les ,h4 ,,smi?1 ,m4 ,e4 7,cornell7 ,,head ,,( ,,! ,,dep>tm5t ,,( ,,physics ,,& ,,assi/ant ,,pr9cipal1 ,,hyde ,,p>k ,,s*ool1 ,,*icago ,,*>les ,m4 ,,turton1 ,a4 ,m4 7,syracuse7 ,,head ,,( ,,! ,,dep>tm5t ,,( ,,physics1 ,,b[5 ,,high ,,s*ool1 ,,*icago ,,9 ,,collaboration ,,) ,,?omas ,d4 ,,cope1 ,ph4,d4 7,p5nsylvania7 ,,assi/ant ,,pr(essor ,,( ,,physics1 ,,univ]sity ,,( ,,p5nsylvania ,,bas$ ,,^u ,,pr9ciples ,,( ,,physics ,,by ,,t[]1 ,,smi? & ,,turton ,,) #g ,,plates ,,& #ddh ,,o!r ,,illu/rations ,,philadelphia ,p4 ,,blaki/on',s ,,son ,,co4 #ajab ,,walnut ,,/reet ,,copyright1 #aibj1 ,,by ,p4 ,,blaki/on',s ,,son ,,co4 ,,preface ,9 ! prep>ation ( ?is text1 ! pupil1 8 exp]i5ce1 ne$s1 & int]e/s h be5 con/antly kept 9 m9d4 ,! ord] ( topics1 illu/rations1 & problems h be5 select$ ) ! purpose ( lead+ ! pupil into a cle> und]/&+ ( ! physical ph5om5a cont9ually tak+ place ab\t him4 ,! recomm5dations & conclusions rea*$ by ! ,new ,movem5t 9 ! ,tea*+ ( ,physics h be5 incorporat$ into ! book z a :ole4 ,^! conclusions indicate t ! mo/ effici5t tea*+ 9 physics involves a dep>ture f ! quantitative1 ma!matical me?ods ( pres5tation t 7 9 g5]al use a doz5 or m ye>s ago1 t[>d a me?od bett] adapt$ to ! capabilities1 int]e/s1 & requirem5ts ( ! "y p 9 our physics classes4 ,! old] me?ods are effective ) a portion ( ! /ud5t body :i* has ! great] ma!matical ability & tra9+1 b !y disc\rage a l>ge majority ( ! pupils :o are n gift$ or prep>$ = sev]e ma!matical analysis4 ,= ?is reason1 _m ( ! m difficult ma!matical demon/rations (t5 giv5 9 physics texts are omitt$4 ,mo/ ( ! problems involve only ! units employ$ 9 practical e-day measurem5ts4 ,! portions ( ,me*anics t are ord9>ily s difficult = ! av]age pupil are n tak5 up until he has cov]$ consid]able gr\nd ) :i* he is m or less famili> & n until he has become some:at accu/om$ to ! me?ods ( /udy & ! te*nical t]ms ( ! subject4 ,! pupil comes to ! /udy ( physics ) a great numb] ( exp]i5ces & impressions ( physical ph5om5a cont9ually occurr+ ab\t him4 ,9 recognition ( ?is fact1 x has be5 ?\ght be/ to consid] fir/ ! explanation ( common ?+s well kn[n to all pupils1 su* z ! diffusion ( gases1 evaporation ( liquids1 expansion ( bodies :5 heat$1 & capill>y action4 ,s9ce ! molecul> !ory ( matt] is n[ support$ by s _m conclusive evid5ces1 we h n hesitat$ to make free use ( x 9 ! e>ly *apt]s4 ,! applications ( ?is !ory are extremely helpful 9 expla9+ e-day ph5om5a4 ,our exp]i5ce %[s t beg9n]s 9 physics und]/& & apply ?is !ory )\t difficulty4 ,! illu/rations & draw+s h be5 select$ f a p$agogical r ?an a spectacul> po9t ( view4 ,practically all ( !m are new4 ,! problems & ex]cises h be5 select$ = ! di/9ct purpose ( illu/rat+ ! pr9ciples taught 9 ! text & = _! practical applications4 ,_m direct applications to common e-day exp]i5ces are giv5 9 ord] to connect ! subject matt] ) ! home environm5t & daily obs]vation ( physical ph5om5a4 ,"s ph5om5a are m5tion$ )\t detail$ explanation z x is felt t ! pres5tation ( ^! subjects 9 ?is mann] is bett] = ?is grade ( /ud5t ?an a complete analysis4 ,"s ( ! special features ( ! text may be briefly summ>iz$ z foll[s3 7,a7 ,simplicity ( pres5tation is emphasiz$4 ,! me?ods ( attack1 ! illu/rations & examples employ$ 9 develop+ ! subjects are p>ticul>ly adapt$ to beg9n]s 9 physics4 7,b7 ,! text is divid$ into "s sev5ty-sev5 sections1 ea* conta9+ mat]ial en\gh = "o recitation4 7,c7 ,ea* ( ^! sections is summ>iz$ by a li/ ( important topics :i* po9t out to ! pupil ! pr9ciples & subject matt] requir+ mo/ c>eful att5tion4 ,! li/s ( important topics are also ( assi/ance to ! tea*] 9 assign+ recitations4 7,d7 ,! problems & practical ex]cises emphasize physical pr9ciples z di/+ui%$ f ma!matical tra9+4 ,a li/ ( ex]cises is plac$ at ! end ( ! sev]al sections4 ,!y are 9 suffici5t numb] to p]mit te/+ at _m po9ts & ( a *oice ( problems by tea*]s4 ,! au?ors wi% to express _! appreciation = sugge/ions & helpful criticisms to _m :o h read ! text 9 manuscript or pro(4 ,especially to ,pr(essor ,a4 ,p4 ,c>man ( ! ,univ]sity ( ,ill9ois & 8 associate1 ,pr(essor ,f4 ,r4 ,watson1 :o h gone c>efully ov] ! :ole text2 & to ,mr4 ,*as4 ,m4 ,brunson1 ,scott ,high ,s*ool1 ,tol$o1 ,ohio1 ,mr4 ,frank ,e4 ,goodell1 ,nor? ,high ,s*ool1 ,des ,mo9es1 ,i[a1 & to ,mr4 ,walt] ,r4 ,ahr5s1 ,englewood ,high ,s*ool1 ,*icago1 = assi/ance 9 read+ ! pro(s4 ,also to ,mr4 ,w4 ,h4 ,coll9s1 ,jr41 ,b[5 ,high ,s*ool1 ,*icago1 :o sup]vis$ ! prep>ation ( draw+s = ! diagrams & figures2 & to _m firms & individuals t h c\rte\sly furni%$ mat]ial = illu/rations4 ,,willis ,e4 ,,t[]4 ,,*>les ,h4 ,,smi?4 ,,*>les ,m4 ,,turton4 ,,on ,,! ,,/udy ,,( ,,physics ,:5 a pupil beg9s ! /udy ( ,physics he has 9 8 possession _m bits ( k :i* are fundam5tal 9 ! sci5ce4 ,he has le>n$ to ?r[ a ball & c tell h[ a ?r[n ball moves4 ,he has drawn out nails ) a claw hamm]4 ,he has se5 wood float & iron s9k4 ,he has suck$ liquids up ?r\gh /raws4 ,9 8 "m's kit*51 he sees wat] z ice1 liquid1 & /eam4 ,on a w9try day he reads ! temp]ature on a !rmomet]4 ,he sees sp>ks fly f c> :eels :5 ! brakes are appli$4 ,he has play$ ) a horse%oe magnet1 & has f\nd ! nor? by means ( a compass4 ,! telephone1 ! electric light & ! motor he sees1 & p]haps uses1 _m times a day4 ,he dresses be=e a mirror1 focuses 8 cam]a1 wat*es ! images at a mov+ picture %[1 & admires ! colors ( ! ra9b[4 ,he has ca/ /ones into wat] to wat* ! ripples spread1 has %\t$ to he> ! e*o1 & p]haps plays "s musical in/rum5t4 ,^!1 & a ?\s& o!r ?+s1 are kn[n to ! intellig5t & normal boy or girl :o has rea*$ ! age at :i* ! /udy ( ,physics is prop]ly begun4 ,to a great ext5t ev5 ! t]ms us$ 9 ! sci5ce are famili> to ! beg9n]4 ,he speaks ( ! horse-p[] ( an eng9e1 reads kil[att-h\rs f ! met] 9 ! cell>1 & may "k t illum9at+ gas co/s "o doll> p] ?\s& cubic feet4 ,amp]e & volt are words he frequ5tly he>s & sees4 ,:5 he takes up ! /udy ( ,physics1 ! attitude ( ! /ud5t t[>d ^! famili> ?+s & words mu/ und]go a *ange4 ,casual in=mation ab\t !m mu/ be *ang$ to s\nd k1 purposely acquir$4 ,hazy notions ab\t ! mean+s ( words mu/ be replac$ by exact def9itions4 ,bits ( k mu/ be built into a /ructure 9 :i* ea* fact f9ds its prop] place 9 relation to ! o!rs4 ,! only ag5t :i* c accompli% ^! *anges is ! /ud5t himself4 ,he mu/ consci\sly & purposely seek ! tru? & mu/ reflect ^u x until he sees x 9 its relation to o!r tru?4 ,^u him1 & ^u him alone1 re/s ! f9al responsibility = ! success or failure ( 8 /udy4 ,b ! /ud5t is n )\t assi/ance4 ,9 8 tea*] he f9ds a guide to /imulate1 to direct1 & to aid 8 ef=ts1 & a critic to po9t out :]e9 8 ef=ts h fail$ & :]e9 !y h succe$$4 ,weights1 measures1 & o!r app>atus are furni%$ to enable him to answ] = himself que/ions :i* h aris5 9 8 /udies4 ,9 addition to ^! ! /ud5t has 8 text book1 8 tea*] = 8 h\rs ( private /udy4 ,a good text book is an inspir+ tea*] 9 pr9t4 ,x directs att5tion to ?+s famili> to ! /ud5t ?r\gh long exp]i5ce1 & inspires him to make a clos] scrut9y ( !m4 ,x invites him to obs]ve1 to analyze1 to comp>e1 to discov] lik5esses & diff]5ces 9 behavior4 ,x que/ions him at e turn4 ,its ev] repeat$ *all5ge reads1 ,weigh & consid]4 ,x furni%es him ne$$ in=mation t he _c o!rwise acquire4 ,x satisfies 8 desire to "k1 ,by :om1 :]e1 :51 & h[ 0 ?is fir/ discov]$8 ,! /ud5t ( ,physics mu/ nev] =get t he is /udy+ n pages ( text b ! behavior & prop]ties ( iron1 wat]1 mica1 mov+ balls1 pumps1 boil+ liquids1 compress$ air1 mirrors1 /eam eng9es1 magnets1 dynamos1 viol9s1 flutes1 & a ho/ ( o!r ?+s4 ,8 /udies %\ld1 :5ev] possible1 be made fir/ h& ^u ! ?+s !mselves4 ,! text is an aid to /udy1 nev] a sub/itute = ! ?+ /udi$4 ,x is an excell5t plan = ea* /ud5t to select "s "o ?+ = special /udy1 ! telephone = example4 ,by obs]vation1 exp]im5t1 & read+1 he may acquire a l>ge am\nt ( valuable in=mation ab\t su* a subject :ile pursu+ 8 c\rse 9 ,physics4 ,e "p ( ! sci5ce w be f\nd to be> "s relation to x4 ,! /ud5t :o takes up ! /udy ( ,physics 9 ! way sugge/$ w f9d himself at ! end ( a ye> ( /udy 9 possession ( mu* new & valuable k ab\t ! physical _w 9 :i* he lives4 ,by virtue ( ?is k he w be bett] able to enjoy ! _w1 to control x1 & to use x4 ,,?omas ,d4 ,,cope4 ,,philadelphia4 ,,cont5ts ,,*apt] ,i4 ,,introduction ,,& ,,measurem5t4 ,,page 7#a7 ,introduction #a 7#b7 ,/ates ( ,matt] #d 7#c7 ,! ,metric ,sy/em #h ,,*apt] ,,ii4 ,,molecul> ,,=ces ,,& ,,motions4 7#a7 ,molecul> ,motions 9 ,gases #ac 7#b7 ,molecul> ,motions 9 ,liquids #ah 7#c7 ,molecul> ,=ces 9 ,liquids #ba 7#d7 ,molecul> ,=ces 9 ,liquids & ,solids #bg 7#e7 ,molecul> ,=ces 9 ,solids #ca ,,*apt] ,,iii4 ,,me*anics ,,( ,,liquids4 7#a7 ,liquid ,pressure #cf 7#b7 ,transmission ( ,liquid ,pressure #da 7#c7 ,ar*im$es' ,pr9ciple #dg 7#d7 ,d5sity & ,specific ,gravity #eb ,,*apt] ,,iv4 ,,me*anics ,,( ,,gases4 7#a7 ,weight & ,pressure ( ! ,air #ee 7#b7 ,compressibility & ,expansibility ( ! ,air #fb 7#c7 ,pneumatic ,appliances #ff ,,*apt] ,v4 ,,=ce ,,& ,,motion4 7#a7 ,=ce1 h[ ,measur$ & ,repres5t$ #gi 7#b7 ,motion4 ,newton's ,laws #he 7#c7 ,resolution ( ,=ces #if 7#d7 ,mom5t ( ,=ce & ,p>allel ,=ces #ii 7#e7 ,gravitation & ,gravity #ajc 7#f7 ,fall+ ,bodies #aji 7#g7 ,! ,p5dulum #aae ,,*apt] ,,vi4 ,,"w ,,& ,,en]gy4 7#a7 ,"w & ,en]gy #aai 7#b7 ,p[] & ,en]gy #abc 7#c7 ,! ,lev] & ,simple ,ma*9es #abi 7#d7 ,:eel & ,axle & ,pulley #acf 7#e7 ,effici5cy & ! ,incl9$ ,plane #adb 7#f7 ,friction & its ,uses #adg 7#g7 ,wat] ,p[] #aeb ,,*apt] ,,vii4 ,,heat1 ,,its ,,production ,,& ,,transmission4 7#a7 ,s\rces & ,effects ( ,heat #aei 7#b7 ,temp]ature & ,expansion #afb 7#c7 ,expansion ( ,gases1 ,liquids & ,solids #afg 7#d7 ,modes ( ,transmitt+ ,heat #agc 7#e7 ,convection1 ,heat+ & ,v5tilation #agi 7#f7 ,! ,moi/ure 9 ! ,air1 ,hygrometry #aia 7#g7 ,evaporation #aif ,,*apt] ,,viii4 ,,heat ,,& ,,"w4 7#a7 ,heat ,measurem5t & ,specific ,heat #bjj 7#b7 ,heat & ,*anges ( ,/ate #bje 7#c7 ,heat & ,"w #bab 7#d7 ,heat ,eng9es #bbb ,,*apt] ,,ix4 ,,magnetism4 7#a7 ,g5]al ,prop]ties ( ,magnets #bbh 7#b7 ,!ory ( ,magnetism1 ,magnetic ,fields #bcb 7#c7 ,! ,e>?'s ,magnetism #bch ,,*apt] ,,xi4 ,,/atic ,,electricity4 7#a7 ,electrification & ,electrical ,*>ges #bdc 7#b7 ,electric ,fields & ,electro/atic ,induction #bdg 7#c7 ,electric ,!ories1 ,di/ribution & ,electric ,*>ges #beb 7#d7 ,pot5tial1 ,capacity1 & ! ,electric ,cond5s] #beg 7#e7 ,electro/atic ,g5]ators #bfb ,,*apt] ,,xi4 ,,electric ,,curr5ts ,,produc$ ,,by ,,voltaic ,,cells4 7#a7 ,electrical ,curr5ts & ,circuits #bfg 7#b7 ,! ,simple ,voltaic ,cell & its ,action #bgj 7#c7 ,practical ,voltaic ,cells #bgd ,,*apt] ,,xii4 ,,magnetic ,,effects ,,( ,,electric ,,curr5ts1 ,,& ,,electrical ,,measurem5ts4 7#a7 ,! ,magnetic ,effect ( ,electric ,curr5ts #bgi 7#b7 ,electrical ,measurem5ts #bhi 7#c7 ,ohm's ,law & ,electrical ,circuits #bih 7#d7 ,gr\p+ ( ,cells & ,measur+ ,resi/ance #cjb ,,*apt] ,,xiii4 ,,*emical ,,& ,,heat ,,effects ,,( ,,electric ,,curr5ts4 7#a7 ,! ,*emical ,effect ( ,electric ,curr5ts #cjg 7#b7 ,! ,/orage ,batt]y & ,electric ,p[] #cab 7#c7 ,! ,heat ,effect ( ,electric ,curr5ts #cah ,,*apt] ,,xiv4 ,,induc$ ,,curr5ts4 7#a7 ,electromagnetic ,induction #cbf 7#b7 ,! ,dynamo & ! ,motor #cce 7#c7 ,! ,induction ,coil & ! ,trans=m] #cdc 7#d7 ,! ,telephone #cdi ,,*apt] ,,xv4 ,,s\nd4 7#a7 ,s\nd1 ,s\rce1 ,spe$1 ,m$ia #ced 7#b7 ,waves & ,wave ,motion #ceg 7#c7 ,int5sity & ,pit* ( ,s\nd #cfc 7#d7 ,musical ,scales & ,resonance #cfh 7#e7 ,int]f]5ce1 ,beats1 ,vibration ( ,/r+s #cgd 7#f7 ,tone ,quality1 ,vibrat+ ,plates & ,air ,columns #chd ,,*apt] ,,xvi4 ,,light4 7#a7 ,rectil9e> ,propagation ( ,light #chh 7#b7 ,photometry & ,law ( ,reflection #cic 7#c7 ,mirrors & ,=mation ( ,images #djj 7#d7 ,refraction ( ,light #daj 7#e7 ,! ,=mation ( ,images by ,l5ses #daf 7#f7 ,optical ,in/rum5ts #dbc 7#g7 ,color & ,spectra #dcj 7#h7 ,nature ( ,light #ddb ,,*apt] ,,xvii4 ,,invisible ,,radiations4 7#a7 ,electric waves & ,radioactivity #ddh ,,*apt] ,,xviii4 ,,wireless ,,telephony ,,& ,,alt]nat+ ,,curr5ts4 7#a7 ,wireless ,telephony #dfj 7#b7 ,alt]nat+ ,curr5ts #dff ,,index #dhg ,,physics ,,*apt] ,i ,,introduction ,,& ,,measurem5t 7#a7 ,,introduction #a4 ,physics1 an ,explanation ( ,common ,?+s4--,_m /ud5ts take up ! /udy ( physics expect+ to see wond]ful exp]im5ts ) ! ,x rays1 wireless telegraphy1 dynamos1 & o!r int]e/+ devices4 ,o!rs are dread+ to beg9 a /udy t to !m seems /range & difficult1 because !y fe> x deals ) ideas & pr9ciples t are beyond _! exp]i5ce & h>d to compreh5d4 ,ea* ( ^! classes is surpris$ to le>n t physics is ma9ly an explanation ( common ?+s4 ,x is a /udy t sy/ematizes our k ( ! =ces & *anges ab\t u2 su* z ! pull ( ! e>?1 ! =mation ( dew1 ra9 & fro/1 wat] pressure & pumps1 e*oes & music1 !rmomet]s & eng9es1 & _m o!r ?+s ab\t u ) :i* p are m or less famili>4 ,physics is l o!r s*ool subjects1 su* z ma!matics & language1 9 hav+ its own peculi> vocabul>y & me?ods ( /udy2 ^! w be acquir$ z progress is made 9 ! c\rse4 ,! mo/ useful habit t ! /ud5t ( physics c =m is t ( connect+ or relat+ ea* new idea or fact t is pres5t$ to him to "s obs]vation or exp]i5ce t w illu/rate ! new idea4 ,?is relat+ or connect+ ( ! new ideas to "o's own p]sonal exp]i5ce is n only "o ( ! be/ kn[n means ( cultivat+ ! memory & p[] ( association1 b x is ( especial help 9 a subject su* z physics1 :i* deals ) ! sy/ematic /udy & explanation ( ! facts ( our e-day exp]i5ce4 #b4 ,k--,common & ,sci5tific4--,?is leads to ! di/9ction betwe5 common k & sci5tific k4 ,we all possess common k ( ! ?+s ab\t u1 ga9$ f ! impressions receiv$ by our s5ses1 f read+1 & f ! rem>ks ( o!rs4 ,sci5tific k is atta9$ :5 ! bits ( common k are connect$ & expla9$ by o!r in=mation ga9$ ?r\gh /udy or exp]i5ce4 ,t is1 common k becomes sci5tific1 :5 x is organiz$4 ,?is leads to ! def9ition3 ,sci5ce is organiz$ k4 ,common k ( ! =ces & objects ab\t u becomes sci5tific only z we are able to make accurate measurem5ts ( ^!4 ,t is1 sci5ce is conc]n$ n only 9 h[ ?+s "w1 b ev5 m 9 h[ mu* is involv$ or results f a giv5 activity4 ,= example1 a sci5tific f>m] mu/ be able to compute 8 co/s & results 9 ord] to det]m9e accurately 8 net pr(its4 ,! bus9ess man :o is conduct+ 8 bus9ess ) effici5cy kn[s accurately 8 co/s ( production & di/ribution4 ,?is book is writt5 9 ! hope t x w make m sci5tific ! /ud5t's common k ( ! =ces & *anges 9 ! _w ab\t him & w give him _m ideas & pr9ciples t w help him to acquire ! habit ( look+ f effects to _! natural causes & ?us t5d to develop :at is call$ ! sci5tific habit ( ?\ght4 #c4 ,hypo!sis1 ,!ory1 & ,law4--,?ree words t are frequ5tly us$ 9 sci5ce may be m5tion$ "h3 hypo!sis1 !ory1 & law4 ,an hypo!sis is a supposition advanc$ to expla9 "s effect1 *ange1 or condition t has be5 obs]v$4 ,= example1 ! ,nebul> ,hypo!sis ( :i* _m high-s*ool /ud5ts h he>d1 is an attempt to expla9 ! orig9 ( ! sun1 ! e>?1 ! planets1 & o!r sol> sy/ems4 ,a !ory is an hypo!sis :i* has be5 te/$ 9 a v>iety ( ways & :i* seems to fit ! conditions & results s t x is g5]ally accept$ z giv+ a satisfactory explanation ( ! matt] 9 "q4 ,! ,molecul> ,!ory ( ,matt] :i* /ates t matt] ( all k9ds is compos$ ( v small p>ticles call$ molecules 7see ,art4 #f71 is a famili> example ( a !ory4 ,a !ory becomes a law :5 x may be def9itely prov$4 ,_m laws are express$ 9 ma!matical language1 e4g41 ! law ( gravitation4 7,see ,art4 #hh47 ,_m ( ! laws ( physics are illu/rat$ by laboratory exp]im5ts1 :i* %[ 9 a simple way j :at ! law means4 ,ex]cises ,expla9 :at is meant by ! foll[+ t]ms & expressions3 #a4 ,common k4 #b4 ,sci5tific k4 #c4 ,sci5ce4 #d4 ,topics 9 physics4 #e4 ,sci5tific habit ( ?\ght4 #f4 ,value ( relat+ new ideas to =m] exp]i5ces4 #g4 ,hypo!sis4 #h4 ,!ory4 #i4 ,law4 7#b7 ,,! ,,/ates ,,( ,,matt] #d4 ,physics ,def9$4--,9 ! /udy ( any sci5ce or field ( k1 x is helpful to h a basis = gr\p+ or classify+ ! facts /udi$4 ,9 physics we are to /udy ! objects1 =ces1 & *anges ab\t u1 to und]/& !m & _! relations to "o ano!r4 ,accord+ly1 physics1 deal+ ) ! mat]ial _w ab\t u1 is (t5 def9$ z ! sci5ce ( matt] & en]gy1 matt] be+ any?+ t occupies space & en]gy ! capacity = do+ "w4 ,?is def9ition ( physics :ile n /rictly accurate is suffici5tly compreh5sive = our pres5t purpose4 #e4 ,! ,?ree ,/ates ( ,matt]4--,our bodies are matt] s9ce !y occupy space4 ,fur!r1 !y possess en]gy s9ce !y are able to d "w4 ,9 beg9n+ ! /udy ( physics x w simplify our "w if we /udy "o ( ^! topics be=e ! o!r4 ,we w !re=e beg9 ) matt] & consid] fir/ its ?ree /ates4 ,"s bodies are solid2 z ice1 iron1 wax4 ,o!rs are liquid2 z wat]1 m]cury1 oil4 ,/ill o!rs are 9 ! /ate ( gas2 z /eam1 air1 & illum9at+ gas4 ,fur!r we notice t ! same sub/ance may be f\nd 9 any "o ( ! ?ree /ates4 ,= example wat] may be ei!r ice1 wat] or /eam2 t is1 ei!r a solid1 a liquid1 or a gas4 ,mo/ p]sons h he>d ( liquid air & possibly "s "k ( ice air1 i4e41 air cool$ until x n only liquefies1 b is solidifi$4 ,on ! o!r h&1 iron may be melt$ &1 if heat$ hot en\gh1 may be turn$ into iron vapor4 ,9 fact mo/ sub/ances by heat+ or cool+ suffici5tly may be *ang$ into any "o ( ! ?ree /ates4 ,be=e def9+ ! ?ree /ates1 let u consid] ! /ructure ( matt]4 ,?is may help u to answ] ! "q3 ,h[ is x possible to *ange a h>d solid1 su* z ice1 into a liquid1 wat]1 & !n into an invisible gas l /eam8 ,?is is expla9$ by ! molecul> !ory ( matt]4 #f4 ,! ,molecul> ,!ory ( ,matt]4--,x is believ$ t all bodies are made up ( v small p>ticles call$ molecules1 & t ^! in/ead ( be+ pack$ tightly toge!r l squ>e packages 9 a box1 are1 /range z x may seem1 v loosely pack$ ev5 9 solids & d n p]man5tly t\* _! neighbors4 ,! size ( ^! molecules is s m9ute t x has be5 e/imat$ t if a drop ( wat] c\ld be magnifi$ to ! size ( ! e>?1 ! molecules magnifi$ 9 ! same proportion w\ld be 9 size betwe5 a baseball & a football4 ,! air & all o!r gases are believ$ to be made up ( molecules 9 rapid motion1 /rik+ & reb\nd+ cont9ually f "o ano!r & f any objects 9 contact ) ! gas4 #g4 ,/ates ( ,matt] ,def9$4--,^! ideas ( ! /ructure ( matt] assi/ u 9 und]/&+ ! foll[+ def9itions3 ,a solid is t /ate ( matt] 9 :i* ! molecules /rongly cl+ toge!r & t5d to keep ! same relative positions4 7,?is ( c\rse foll[s f ! t5d5cy ( a solid to reta9 a def9ite =m47 ,a liquid is t /ate ( matt] 9 :i* ! molecules t5d to cl+ toge!r1 yet move ab\t freely4 ,h5ce a liquid takes ! =m ( any vessel 9 :i* x is plac$4 ,a gas is t /ate ( matt] 9 :i* ! molecules move ab\t freely & t5d to sep>ate indef9itely4 ,h5ce a gas w fill any space 9 :i* x is plac$4 #h4 ,effect ( ,heat on ,matt]4--,x is fur!r believ$ t :5 a body is heat$1 t ! action really consi/s 9 mak+ its molecules move or vibrate fa/] & fa/] z ! heat+ progresses4 ,?is increase ( motion causes ! molecules to pu% ap>t f "o ano!r & ?is sep>ation ( ! molecules causes an expansion ( ! body :e!r x be solid1 liquid1 or gas4 ,fig4 #a %[s ! expansion ( air 9 an air !rmomet]4 ,fig4 #b %[s ! expansion ( a solid on heat+4 ,illu/ration3 ,,fig4 #a4--,:5 ! bulb is heat$1 ! air )9 exp&s =c+ d[n ! wat] 9 ! tube4 #i4 ,physical & ,*emical ,*anges4 ,a *ange ( /ate su* z ! freez+ or boil+ ( wat] is call$ a physical *ange1 = ?is *ange has n affect$ ! id5tity ( ! sub/ance4 ,x is wat] ev5 ?\gh x has become solid or gase\s4 ,heat+ a plat9um wire r$ hot is also a physical *ange = ! wire :5 on cool+ is f\nd to be ! same sub/ance z be=e4 ,fur!r if salt or sug> be dissolv$ 9 wat] ! act ( solution is also a physical *ange s9ce ! id5tical sub/ance 7salt or sug>7 is 9 ! solution & may be obta9$ by evaporat+ ! wat]4 ,illu/ration3 ,,fig4 #b 7a7 repres5ts a /raight b> made ( a /rip ( brass & a /rip ( iron rivet$ toge!r & atta*$ to a h&le4 ,^u heat+ ! comp\nd b> 9 a gas flame1 ! brass exp&s fa/] ?an ! iron caus+ ! b> to b5d t[>d ! latt] z 9 ,fig4 #b 7b74 ,if "s sug>1 h[ev]1 is heat$ /rongly1 say 9 a te/-tube1 x is f\nd to black51 "s wat] is driv5 (f & on cool+ "s black *>coal is f\nd 9 ! tube in/ead ( ! sug>4 ,?is action :i* has result$ 9 a *ange 9 ! nature ( ! sub/ance treat$ is call$ a *emical *ange4 ,to illu/rate fur!r1 if "s magnesium wire is heat$ /rongly 9 a flame1 x burns1 giv+ (f an int5se light & :5 x cools "o f9ds x *ang$ to a light p[d]y sub/ance l a%es4 ,*emical *anges1 or ^? t *ange ! nature ( ! sub/ance affect$1 are /udi$ 9 *emi/ry4 ,9 physics we h to d only ) physical *anges1 t is1 ) ^? *anges t d n affect ! nature ( ! sub/ance4 ,important ,topics #a4 ,physics def9$4 #b4 ,! ?ree /ates ( matt]2 solid1 liquid1 gas4 #c4 ,molecul> !ory ( matt]4 #d4 ,physical & *emical *anges4 ,ex]cises ,write out 9 y\r own words y\r und]/&+ (3 #a4 ,! /ructure ( matt]4 #b4 ,"s ( ! diff]5ces betwe5 solids1 liquids1 & gases4 #c4 ,h[ to *ange solids to liquids & gases & vice v]sa4 #d4 ,! reason = ! *anges ( size ( a body on heat+4 #e4 ,:y cool+ a gas t5ds to *ange x to a liquid or a solid4 #f4 ,! actual size ( molecules4 ,:i* ( ! foll[+ *anges are *emical & :i* physical8 ,give reasons4 #a4 ,melt+ ( ice4 #b4 ,burn+ ( a c&le4 #c4 ,production ( /eam4 #d4 ,fall+ ( a weight4 #e4 ,dry+ ( clo!s4 #f4 ,mak+ an iron ca/+4 #g4 ,decay ( vegetables4 #h4 ,spr\t+ ( se$s4 #i4 ,fly+ an a]oplane4 #aj4 ,gr[? ( a plant4 #aa4 ,gr9d+ ( gra94 #ab4 ,saw+ a bo>d4 #ac4 ,pulv]iz+ /one4 #ad4 ,mak+ toa/4 #ae4 ,sweet5+ tea or c(fee ) sug>4 #af4 ,burn+ wood or gas4 7#c7 ,,! ,,metric ,,sy/em #aj4 ,! ,metric ,sy/em4--,9 ord] to /udy ! ?ree /ates ( matt] ) suffici5t exactness x is necess>y to employ a sy/em ( measurem5t4 ,! sy/em univ]sally employ$ by sci5ti/s is call$ ,! ,metric ,sy/em4 ,9 _m respects x is ! mo/ conv5i5t = all purposes4 ,e /ud5t %\ld !re=e become famili> ) x & le>n to use x4 ,at ! pres5t "t1 n only d sci5ti/s ev]y:]e use x1 b _m c\ntries h adopt$ x & use x 9 common measurem5ts4 ,x 0 legaliz$ 9 ! ,unit$ ,/ates 9 #ahff4 ,! metric sy/em 0 orig9at$ by ! ,fr5* ,academy ( ,sci5ces dur+ ! latt] "p ( ! #ah? c5tury4 ,!re 7 s _m diff]5t sy/ems ( weights & measures 9 use1 ea* c\ntry hav+ a sy/em ( its own1 t comm]ce 0 mu* h9d]$4 ,x 0 !re=e decid$ to make a sy/em bas$ ^u sci5tific pr9ciples4 ,! l5g? ( ! e>?'s quadrant pass+ f ! equator to ! pole 0 det]m9$ by survey+ & computation4 ,"o-t5-million? ( ?is di/ance 0 select$ z ! unit ( l5g? & call$ a met]4 ,accurate copies ( ?is met] 7 made & pres]v$ z /&>ds4 ,lat] surveys h %[n t ! orig9al det]m9ation ( ! e>?'s quadrant 0 n /rictly accurate2 s t aft] all ! met] is n exactly "o-t5-million? ( ! e>?'s quadrant4 #aa4 ,! ,/&>d ,met]4--,! /&>d unit ( l5g? 9 ! metric sy/em is ! met]4 ,x is ! di/ance1 at ! temp]ature ( melt+ ice1 betwe5 two transv]se p>allel l9es rul$ on a b> ( plat9um 7see ,fig4 #c71 :i* is kept 9 ! ,palace ( ! ,ar*ives 9 ,p>is4 ,accurate copies ( ?is & o!r metric /&>ds are also kept at ! ,bureau ( ,/&>ds at ,wa%+ton1 ,d4 ,c4 ,fig4 #d %[s ! relation betwe5 ! in* & ! c5timet] 7"o-hundr$? ( a met]74 #ab4 ,units & ,tables 9 ! ,metric ,sy/em4--,! metric unit ( area commonly us$ 9 physics is ! squ>e c5timet]4 ,illu/ration3 ,,fig4 #c--,! /&>d met]4 ,! /&>d unit ( volume or capacity is ! lit]4 ,x is a cube "o-t5? ( a met] on ea* edge4 ,x is equal to #a4jeg qu>ts4 ,x corresponds1 !re=e1 to ! qu>t 9 ,engli% measure4 ,illu/ration3 ,,fig4 #d4--;,c5timet] & in* scales4 ,! /&>d unit ( mass is ! kilogram4 ,x is ! mass ( #a lit] ( pure wat] at ! temp]ature ( its greate/ d5sity1 #d;,c4 or #ci4b;,f4 ,! ?ree pr9cipal units ( ! metric sy/em1 ! met]1 ! lit]1 & ! kilogram1 are relat$ to "o ano!r 9 a simple mann]1 s9ce ! lit] is a cube "o-t5? ( a met] 9 ea* dim5sion & ! kilogram is ! mass ( a lit] ( wat]4 7,see ,fig4 #e47 ,! metric sy/em is a decimal sy/em t is1 "o unit is relat$ to ano!r unit 9 ! ratio ( t5 or ( "s p[] ( t54 ,?is is indicat$ by ! foll[+ tables3 ,metric ,table ( ,l5g? #aj millimet]s 7mm47 equal #a c5timet]4 #aj c5timet]s 7cm47 equal #a decimet]4 #aj decimet]s 7dm47 equal #a met]4 #aj met]s 7m47 equal #a dekamet]4 #aj dekamet]s 7,dm47 equal #a hectomet]4 #aj hectomet]s 7hm47 equal #a kilomet]4 #aj kilomet]s 7km47 equal #a myriamet]4 ,! measures commonly us$ are ! c5timet]1 met] & kilomet]4 ,metric ,table ( ,mass 7or ,weight7 #aj milligrams 7mg47 equal #a c5tigram4 #aj c5tigrams 7cg47 equal #a decigram4 #aj decigrams 7dg47 equal #a gram4 #aj grams 7g47 equal #a dekagram4 #aj dekagrams 7,dg47 equal #a hectogram4 #aj hectograms 7hg47 equal #a kilogram4 #aj kilograms 7kg47 equal #a myriagram4 ,! masses commonly us$ are ! milligram1 gram & kilogram4 ,notice 9 ^! tables ! simil>ity to #aj mills equal #a c5t1 #aj c5ts equal #a dime1 #aj dimes equal #a doll>1 9 ! table ( ,unit$ ,/ates money4 ,o!r tables 9 ! metric sy/em are built ^u ! same plan4 ,le>n ! prefixes 9 ord] ?us3 milli1 c5ti1 deci1 deka1 hecto1 kilo1 myria4 ,! fir/ ?ree prefixes are ,lat9 num]als & repres5t divisions ( ! unit4 ,! la/ f\r are ,greek num]als & repres5t multiples4 ,9 ^! tables1 milli means #a_/ajjj1 c5ti means #a_/ajj1 deci means #a_/aj1 deka means #aj1 hecto1 #ajj1 kilo1 #ajjj1 myria1 #aj1jjj4 ,two o!r prefixes are sometimes us$1 micro :i* means #a_/a1jjj1jjj2 z micr(>ad or microvolt1 & meg :i* means #a1jjj1jjj1 z megohm mean+ #a1jjj1jjj ohms4 #ac4 ,advantages ( ! ,metric ,sy/em4--,fir/1 x is a decimal sy/em2 second1 ! same =m & prefixes are us$ 9 e table2 ?ird1 ! /&>ds ( l5g? 7met]71 volume 7lit]71 & mass 7kilogram7 be> a simple relation to "o ano!r4 ,?is simple relation betwe5 ! ?ree /&>d units may be giv5 ?us3 fir/1 ! lit] is a cubic decimet]1 & second1 ! kilogram is ! mass ( a lit] ( wat]4 7,see ,fig4 #e7 ,s9ce ! lit] is a cubic decimet]1 ! l5g? ( "o side is #aj cm4 ,! lit] !re=e holds #ajjj ccm4 7#aj #aj #aj74 ,!re=e1 #a lit] #a cu4 dm4 #ajjj ccm4 & s9ce #a lit] ( wat] has a mass ( #a kg4 or #ajjj g41 !n #ajjj ccm4 ( wat] has a mass ( #ajjj g41 or #a ccm4 ( wat] has a mass ( #a g4 ,illu/ration3 ,,fig4 #e4--,"o lit] ( ! wat] has a mass ( "o kilogram4 ,! foll[+ table ( equival5ts gives ! relation betwe5 ! mo/ common ,engli% & metric units4 ,^? m>k$ 7997 %\ld be memoriz$4 7997 #a met] #ci4cg in*es4 #a cu1 94 #af4chg ccm4 7997 #a in* #b4ed cm4 #a cu4 ft4 #bhcae cm4 #a foot #cj4dh cm4 #a cu4 m4 #a4cjh cu4 yd4 #a mile #a4fji km4 7997 #a lit] #a4jeg qt4 #a sq4 94 #f4de sq4 cm4 7997 #a kg4 #b4bjd lbs4 #a sq4 cm4 #j4aee sq4 94 #a g4 #ae4dd gra9s4 #a sq4 m4 #a4aif sq4 yd4 #a lb4 #j4decf kg4 #a acre #j4dje ha4 #a oz4 #bh4ce g4 #a hect>e #b4de acres4 #a g4 #j4jcec oz4 ,,! ,c4 ,g4 ,s4 ,,sy/em4 ,sci5ti/s h devis$ a plan = express+ any measurem5t 9 t]ms ( :at are call$ ! ?ree fundam5tal units ( l5g?1 mass1 & "t4 ,! units us$ are ! c5timet]1 ! gram & ! second4 ,:5ev] a measurem5t has be5 r$uc$ to its equival5t 9 t]ms ( ^! units1 x is said to be express$ 9 ,c4,g4,s4 units4 ,important ,topics #a4 ,! metric sy/em2 h[ orig9at$4 #b4 ,units2 met]1 lit]1 kilogram4 #c4 ,metric tables4 #d4 ,advantages ( ! metric sy/em4 #e4 ,equival5ts4 #f4 ,! ,c4,g4,s4 sy/em4 ,ex]cises #a4 ,:i* is *eap]1 milk at #h c5ts a qu>t or #h c5ts a lit]8 ,:y8 #b4 ,:i* is m exp5sive1 clo? at #a4jj a y>d or at #a4jj a met]8 ,:y8 #c4 ,:i* is a bett] b>ga91 sug> at #e c5ts a p\nd or #aa c5ts a kilogram8 ,:y8 #d4 ,express 9 c5timet]s ! height ( a boy #e ft4 #f 94 tall4 #e4 ,:at is ! l5g? ( ?is page 9 c5timet]s8 ,9 in*es8 #f4 ,:at is ! mass ( a lit] ( wat]8 ,( #ejj ccm48 ,( #a ccm48 #g4 ,f ,*icago to ,new ,york is #idj miles4 ,express 9 kilomet]s4 #h4 ,a #aj-;gallon c ( milk conta9s h[ _m lit]s8 #i4 ,:at w #ajj met]s ( clo? co/ at #aj c5ts a y>d8 #aj4 ,:at w #d kg4 ( beef co/ at #ae c5ts a p\nd8 #aa4 ,:at w #e-a_/b lbs4 ( mutton co/ at #dj c5ts a kilogram8 #ab4 ,h[ c y *ange ! /ate ( a body8 ,give ?ree me?ods4 #ac4 ,correct ! /atem5t #a ccm4 #a g4 #ad4 ,h[ _m lit]s 9 #cb qu>ts8 ,,*apt] ,,ii ,,molecul> ,,=ces ,,& ,,motions 7#a7 ,,evid5ces ,,( ,,molecul> ,,motion ,,9 ,,gases #ad4 ,size ( ,molecules4--,! diff]5ce betwe5 solids1 liquids1 & gases has be5 expla9$ z due to ! diff]5t behavior ( molecules 9 ! ?ree /ates ( matt]4 ,t is1 9 solids !y cl+ toge!r1 9 liquids !y move freely1 & 9 gases !y sep>ate4 ,at ?is "t we are to consid] ! evid5ces ( molecul> motion 9 gases4 ,x mu/ be kept 9 m9d t molecules are exce$+ly small4 ,x has be5 said t if a bottle conta9+ ab\t #a ccm4 ( ord9>y air has pi]c$ 9 x a m9ute op5+ s t #ajj1jjj1jjj molecules 7a numb] ne>ly equal to ! population ( ! ,unit$ ,/ates7 pass out e second1 x w\ld take1 n m9utes or h\rs1 b ne>ly #ijjj ye>s = all ( ! molecules to escape4 ,! numb] ( molecules 9 #a ccm4 ( air at #j;,c4 & #gf cm4 pressure has be5 calculat$ by ,pr(essor ,ru!r=d to be #b4g #aj4 ,x is evid5t t su* m9ute p>ticles _c be se5 or h&l$ z individuals4 ,we mu/ judge ( _! size & action by ! results obta9$ f exp]im5ts4 #ae4 ,diffusion ( ,gases4--,"o l9e ( evid5ce :i* indicates t a gas consi/s ( mov+ p>ticles is ! rapidity ) :i* a gas hav+ a /rong odor p5etrates to all p>ts ( a room4 ,= example1 if illum9at+ gas is escap+ x soon diffuses & is notic$ ?r\gh\t ! room4 ,9 fact1 ! common exp]i5ce ( ! diffusion ( gases hav+ a /rong odor is su* t we promptly recognize t x is due to motion ( "s k9d4 ,! gas hav+ ! odor consi/s ( little p>ticles t are cont9ually hitt+ _! neighbors & are be+ /ruck & buffet$ 9 turn until ! individual molecules are widely scatt]$4 ,:5 cabbage is boil$ 9 ! kit*5 soon all 9 ! h\se "k x4 ,o!r illu/rations ( ! diffusion ( gases w occur to anyone f p]sonal exp]i5ce1 su* = in/ance z ! pleas+ odor f a field ( clov] 9 bloom4 ,! foll[+ exp]im5t illu/rates ! rapid diffusion ( gases4 ,illu/ration3 ,,fig4 #f;a4--,diffusion ( gases4 ,illu/ration3 ,,fig4 #f;b4--,effusion ( gases4 ,take two tumbl]s 7see ,fig4 #f;a71 wet ! inside ( "o ) a few drops ( /rong ammonia wat] & ! o!r ) a little hydro*loric acid4 ,cov] ea* ) a %eet ( clean pap]4 ,no?+ c n[ be se5 9 ei!r tumbl]4 ,inv]t ! second "o ov] ! fir/ ) ! pap] betwe51 plac+ !m s t ! edges w mat*4 ,on remov+ ! pap] x is notic$ t bo? tumbl]s are quickly fill$ ) a cl\d ( f9ely divid$ p>ticles1 ! two sub/ances hav+ unit$ *emically to =m a new sub/ance1 ammonium *loride4 ,on acc\nt ( _! small size1 molecules ( air readily pass ?r\gh por\s solids1 clo?1 unglaz$ e>!nw>e1 etc4 ,! foll[+ exp]im5t %[s ?is fact /rik+ly4 7,see ,fig4 #f;b47 ,a flask conta9+ wat] is clos$ by a rubb] /opp] ?r\gh :i* pass ! /em ( a glass funnel & a b5t glass tube t has be5 drawn out to a small op5+ 7,j74 ,! funnel has cem5t$ 9 its top an inv]t$ por\s clay j> 7,c71 ov] ! top ( ! latt] is plac$ a beak] 7,b74 ,a piece ( flexible rubb] tub+ 7,h7 lead+ f a hydrog5 g5]ator is br\ght up to ! top ( ! space betwe5 ! j> & ! beak]4 ,:5 hydrog5 gas is all[$ to fl[ into ! space betwe5 ,c & ,b1 ! level ( ! wat] 9 ,w is se5 to l[] & a /ream ( wat] runs out at ,j spurt+ up into ! air4 ,on /opp+ ! fl[ ( hydrog5 & remov+ ,b1 ! wat] falls rapidly 9 ,j & bubbles ( air are se5 to ent] ! wat] f ! tube4 7,! =ego+ /eps may be repeat$ z (t5 z desir$74 ,?is exp]im5t illu/rates ! fact t ! molecules ( "s gases move fa/] ?an ^? ( "s o!r gases4 ,hydrog5 molecules are f\nd to move ab\t f\r times z fa/ z air molecules4 ,h5ce1 :ile bo? air & hydrog5 molecules are at fir/ go+ 9 opposite directions ?r\gh ! walls ( ,c1 ! hydrog5 goes 9 mu* fa/] ?an ! air comes out4 ,9 consequ5ce x accumulates1 creates pressure1 & drives d[n ! wat] 9 ,w & out at ,j4 ,on remov+ ,b1 ! hydrog5 )9 ! por\s cup comes out mu* fa/] ?an ! air rent]s4 ,?is less5s ! pressure )91 s t air ru%es 9 ?r\gh ,j4 ,?is exp]im5t demon/rates n only ! fact ( molecul> motion 9 gases b also t molecules ( hydrog5 move mu* fa/] ?an ^? ( air4 7,?is exp]im5t w "w ) illum9at+ gas b n s /rik+ly47 ,c>eful exp]im5ts h %[n t ! spe$ ( ord9>y air molecules is #dde met]s or #adfj ft4 p] second2 :ile hydrog5 molecules move at ! rate ( #agjj met]s or #eege ft4 or m ?an a mile p] second4 #af4 ,expansion ( ,gases4--,gases also possess ! prop]ty ( indef9ite expansion1 t is1 if a small quantity ( gas is plac$ 9 a vacuum1 ! gas w exp& imm$iately to fill ! entire space uni=mly4 ,?is is %[n by an exp]im5t ) ! air pump4 ,on rais+ ! pi/on ! air foll[s in/antly to fill up ! space "u x4 ,z ! air is remov$ f ! receiv] ( an air pump ! air rema9+ is uni=mly di/ribut$ )94 #ag4 ,h[ ,gases ,ex]t ,pressure4--,x is fur!r f\nd t air "u ord9>y conditions ex]ts a pressure ( ab\t #ae lbs4 to ! squ>e in*4 ,9 an automobile tire ! pressure may be #ij lbs4 & 9 a /eam boil] x may be #bjj lbs4 or m to ! squ>e in*4 ,h[ is ! pressure produc$8 ,! molecules are n pack$ toge!r solidly 9 a gas1 = :5 /eam *anges to wat] x %r9ks to ab\t #a_/afjj ( its =m] volume4 ,air dim9i%es to ab\t #a_/hjj ( its volume on *ang+ to liquid air4 ,! pressure ( a gas is n due !n to ! gas fill+ all ( ! space 9 :i* x acts1 b is due r to ! motion ( ! molecules4 ,! bl[ ( a s+le molecule is imp]ceptible1 b :5 multitudes ( molecules /rike aga9/ a surface _! comb9$ effect is consid]able4 ,9 fact1 ?is action is kn[n to produce ! pressure t a gas ex]ts aga9/ ! walls ( a conta9+ vessel4 ,naturally if we compress twice z mu* gas into a giv5 space !re w be twice z _m molecules /rik+ 9 a giv5 "t1 :i* w give twice z mu* pressure4 ,if gas is heat$1 x is f\nd t ! heat w cause a swift] motion ( ! molecules4 ,?is w also make ! molecules /rike h>d] & h5ce cause ! gas to exp& or ex]t m pressure4 #ag;a4 ,br[nian ,movem5ts4--,direct photographic evid5ce ( ! motion ( molecules 9 gases has be5 obta9$ by /udy+ ! behavior ( m9ute drops ( oil susp5d$ 9 /agnant air4 ,su* drops in/ead ( be+ at re/ are con/antly danc+ ab\t z if !y 7 cont9ually receiv+ bl[s f _m directions4 ,^! motions h be5 call$ ,br[nian ,movem5ts 7see ,fig4 #g74 ,x has be5 prov$ t ^! movem5ts are due to ! bl[s t ^! small drops receive f ! swiftly mov+ molecules ( ! gas ab\t !m4 ,if ! drops are made small] or ! gas m d5se1 ! movem5ts increase 9 int5sity4 ,^! effects are especially m>k$ at a pressure ( #j4ja ( an atmosph]e4 ,illu/ration3 ,,fig4 #g4--,photograph ( ,br[nian movem5t4 ,?is record is prep>$ by ! aid ( ,si$5topf's ultra-microscope & a plate mov+ uni=mly across ! field f left to "r4 ,important ,topics ,x is assum$ t air & all gases are made up ( molecules 9 rapid motion2 t ?is motion is dep5d5t ^u temp]ature & pressure4 ,evid5ce ( ?is is %[n by 7a7 diffusion1 7b7 expansion1 7c7 pressure4 ,br[nian ,movem5ts4 ,que/ions #a4 ,:at is ! molecul> 7k9etic7 !ory ( gases8 #b4 ,:at ?ree k9ds ( evid5ce help to confirm ! !ory8 #c4 ,:at h y se5 t seems to %[ t a gas consi/s ( molecules 9 motion8 #d4 ,h[ _m met]s long is a #aj-;ft4 pole8 #e4 ,a #ej-kg4 boy weighs h[ _m p\nds8 #f4 ,:at are ?ree advantages ( ! metric sy/em8 #g4 ,:at w #ab qts4 ( milk co/ at #h c5ts a lit]8 #h4 ,a cube #a met] ea* way w conta9 h[ _m cubic c5timet]s8 ,h[ _m lit]s8 ,:at w a cubic met] ( wat] weigh8 7#b7 ,,molecul> ,,motion ,,9 ,,liquids #ah4 ,diffusion ( ,liquids4--,f ! evid5ce giv5 9 ,arts4 #ad-ag1 7a7 ( diffusion ( odors1 7b7 ( ! cont9u$ expansion ( air 9 ! air pump1 & 7c7 ( ! pressure ex]t$ by a gas 9 all directions1 "o may realize )\t difficulty t a gas consi/s ( small p>ticles 9 rapid motion4 ,let u n[ consid] "s ( ! evid5ce ( molecul> motion 9 liquids4 ,if a little v9eg> is plac$ 9 a pail ( wat]1 all ( ! wat] w soon ta/e s\r4 ,a lump ( sug> 9 a cup ( tea w sweet5 ! entire cont5ts4 ,?is action is some:at simil> to ! diffusion ( gases b x takes place mu* m sl[ly4 ,x is !re=e believ$ t ! motion ( liquid molecules is mu* sl[] ?an t ( gas molecules4 ,aga91 if a di% ( wat] is left /&+ 9 ! op5 air 9 f9e wea!r1 )9 a few days ! di% w become dry ?\gh no "o has tak5 any?+ f x4 ,we say ! wat] has evaporat$4 ,:at 0 liquid is n[ vapor4 ,if we 7 to obs]ve c>efully any di% ( wat] we w\ld f9d t x cont9ually loses weight on dry days4 ,t is1 !re is a con/ant movem5t ( ! molecules ( wat] into ! air4 ,?is movem5t ( ! molecules is expla9$ z foll[s4 ,!re appe> to be 9 ! di% ( wat] "s molecules t by mov+ back & =? acquire a great] velocity ?an _! neighbors2 :5 ^! rea* ! surface ( ! liquid1 "s vibration or movem5t s5ds !m fly+ into ! air above4 ,!y are n[ vapor or gas molecules1 fly+1 /rik+1 & reb\nd+ l ! air molecules4 ,sometimes on reb\nd+1 ! wat] molecules get back into ! wat] aga94 ,?is is especially apt to happ5 :5 ! air is damp1 i4e41 :5 x conta9s _m wat] molecules4 ,sometimes ! air ov] a di% becomes saturat$1 z 9 ! upp] "p ( a cork$ bottle conta9+ wat]4 ,al?\gh molecules are cont9ually leav+ ! surface ( ! wat] !y _c escape f ! bottle1 s 9 "t z _m molecules mu/ return to ! wat] f ! space above z leave ! wat] 9 ! same "t4 ,:5 ?is condition exi/s1 ! air above ! wat] is said to be saturat$4 ,on v damp days ! air is (t5 saturat$4 ,! explanation above %[s :y wet clo!s dry s sl[ly on su* a day 7,see ,arts4 #aff-g on ,saturation47 #ai4 ,cool+ ,effect ( ,evaporation4 ,we h se5 t w>m+ a gas increases its volume4 ,?is expansion is due to ! increas$ motion ( ! w>m$ molecules4 ,n[ ! molecules t escape f a liquid :5 x evaporates are naturally ! fa/e/ mov+ ones1 i4e41 ! hotte/ ones4 ,! molecules rema9+ are ! sl[] mov+ ones or cold] molecules4 ,! liquid !re=e becomes cold] z x evaporates1 unless x is heat$4 ,?is expla9s :y wat] evaporat+ on ! surface ( our bodies cools u4 ,9 evaporat+1 ! wat] is cont9ually los+ its w>m1 fa/ mov+ molecules4 ,! cool+ effect ( evaporation is1 !re=e an evid5ce ( molecul> motion 9 liquids4 ,illu/ration3 ,,fig4 #h4--,osmosis ,%[n by c>rot plac$ 9 wat]4 #bj4 ,osmosis4--,if two liquids are sep>at$ by a membrane or por\s p>tition1 !y t5d to pass ?r\gh & mix4 ,?is action is call$ osmose1 or osmosis4 ,su* a movem5t ( liquid molecules 9 osmosis may be illu/rat$ by fill+ a beet or c>rot t has _h its int]ior cut out to =m a circul> op5+ 7see ,fig4 #h7 ) a ?ick syrup4 ,! op5+ is !n clos$ at ! top ) a rubb] /opp] ?r\gh :i* passes a long glass tube4 ,if ! c>rot is imm]s$ 9 wat]1 z 9 ,fig4 #h1 a movem5t ( wat] ?r\gh ! por\s wall to ! int]ior beg9s at once4 ,"h1 z 9 ! exp]im5t ( ! hydrog5 & air pass+ ?r\gh ! por\s cup1 ! light] fluid moves fa/]4 ,! wat] collect+ 9 ! c>rot rises 9 ! tube4 ,?is action ( liquids pass+ ?r\gh por\s p>titions & m+l+ is call$ osmosis4 ,gases & liquids are alike 9 t ea* w fl[4 ,ea* is !re=e call$ a fluid4 ,sometimes !re is mu* resi/ance to ! fl[ ( a liquid z 9 molasses4 ,?is resi/ance is call$ viscosity4 ,alcohol & gasol9e h little viscosity4 ,!y are limpid or mobile4 ,air also has "s viscosity4 ,= in/ance1 a /ream ( air always drags "s ( ! surr\nd+ air along ) x4 ,important ,topics #a4 ,liquids behave z if !y 7 compos$ ( small p>ticles 9 motion4 #b4 ,?is is %[n by 7#a7 ,diffusion1 7#b7 ,solution1 7#c7 ,evaporation1 7#d7 ,expansion1 7#e7 ,osmosis4 ,ex]cises #a4 ,give an example or illu/ration ( ea* ( ! five evid5ces ( molecul> motion 9 liquids4 #b4 ,:5 is air saturat$8 ,:at is ! explanation8 #c4 ,:y does w>m+ a liquid increase its rate ( evaporation8 #d4 ,air molecules are 9 rapid motion 9 all directions4 ,d !y ent] a liquid ) a surface expos$ to ! air8 ,give reason4 #e4 ,:at are "s ( ! inconv5i5ces ( liv+ 9 a saturat$ atmosph]e8 #f4 ,fi% require oxyg54 ,h[ is x obta9$8 7#c7 ,,molecul> ,,=ces ,,9 ,,liquids #ba4 ,cohesion & ,adhesion4--,9 liquids ! molecules move ab\t freely yet t5d to cl+ toge!r4 ,?is t5d5cy ( molecules to cl+ toge!r :i* is n noticeable 9 gases is *>act]i/ic ( liquids & especially ( solids4 ,x is ! cause ( ! viscosity m5tion$ 9 ! previ\s section & is readily detect$ 9 a v>iety ( ways4 ,= in/ance1 n only d liquid molecules cl+ toge!r to =m drops & /reams1 b !y cl+ to ! molecules ( solids z well1 z is %[n by ! wet surface ( an object t has be5 dipp$ 9 wat]4 ,! attraction ( l molecules = "o ano!r is call$ cohesion1 :ile ! attraction ( unlike molecules is call$ adhesion1 al?\gh ! =ce is ! same :e!r ! molecules are alike or unlike4 ,x is ! =m] t causes drops ( wat] to =m & t holds iron1 copp]1 & o!r solids s rigidly toge!r4 ,! adhesion ( glue to o!r objects is well kn[n4 ,pa9t also /icks well4 ,sometimes ! jo9t :]e two bo>ds are glu$ toge!r is /rong] ?an ! bo>d itself4 ,! =ce ( attraction betwe5 molecules has be5 /udi$ c>efully4 ,! attraction acts only ?r\gh v %ort di/ances4 ,! attraction ev5 9 liquids is consid]able & may be measur$4 ,! cohesion ( wat] may be %[n by an exp]im5t :]e ! =ce requir$ to pull a glass plate f ! surface ( wat] is measur$4 ,illu/ration3 ,,fig4 #i4--,! wat] is pull$ ap>t4 ,take a beam balance & susp5d f "o arm a circul> glass plate1 ,fig4 #i4 ,weigh ! plate & its support4 ,adju/ ! glass plate s t x hangs horizontally & j t\*es ! surface ( clean wat]1 ! "u side be+ completely wet4 ,n[ f9d :at additional weight is requir$ to raise ! glass plate f ! wat]4 ,j z ! plate comes f ! wat] its "u side is f\nd to be wet4 ,t is1 ! wat] 0 pull$ ap>t1 & ! plate 0 n pull$ f ! wat]4 ,! cohesion ( ! wat] to itself is n s /rong z its adhesion to ! glass4 ,! cohesion ( liquids is fur!r %[n by ! =m a drop ( liquid t5ds to take :5 left to itself4 ,?is is readily se5 9 small drops ( liquids4 ,! sph]ical %ape ( drops ( wat] or m]cury is an example4 ,a mixture ( alcohol & wat] 9 prop] proportions w j support olive oil )9 x4 ,by c>efully dropp+ olive oil f a pipette into su* a mixture1 a drop ( ! oil1 an in* or m 9 diamet] susp5d$ 9 ! liquid1 may be =m$4 ,x is be/ to use a bottle ) plane or flat sides1 = if a r\nd bottle is us$1 ! sph]e ( oil w appe> flatt5$4 ,illu/ration3 ,,fig4 #aj a4 ,,fig4 #aj b4 ,,figs4 #aj a ,,& b4--,surface t5sion ( a liquid film4 #bb4 ,surface ,t5sion4--,! cohesion ( liquids is also indicat$ by ! t5d5cy ( films to assume ! smalle/ possible surface4 ,soap bubble films %[ ?is readily4 ,fig4 #aj a repres5ts a circul> wire =m hold+ a film 9 :i* floats a loop ( ?read4 ,! t5sion ( ! film is %[n 9 ,fig4 #aj b by ! circul> =m ( ! loop aft] ! film )9 x has be5 pi]c$ by a hot wire1 ,fig4 #aa %[s a rectangul> wire =m ) a rid]4 ,! t5sion 9 ! film draws ! rid] =w>d4 ,illu/ration3 ,,fig4 #aa4--,! rid] is drawn =w>d4 ,illu/ration3 ,,fig4 #ab4--,surface t5sion causes ! po9t$ %ape4 ,a soap bubble takes its sph]ical %ape because ?is =m holds ! conf9$ air )9 ! smalle/ possible surface4 ,a drop ( liquid is sph]ical = ! same reason4 ,_m illu/rations ( ! t5sion 9 films may be giv54 ,us]s ( wat] colors notice t a dry camel's-hair bru% is bu%y4 7,fig4 #ab ,a74 ,:5 9 wat] x is /ill bu%y4 7,fig4 #ab ,b47 ,b :5 x is tak5 f ! wat] & ! excess is %ak5 f x1 x is po9t$ z 9 ,fig4 #ab ,c4 ,x is held to ! po9t$ %ape by ! t5sion ( ! liquid film ab\t ! bru%4 ,illu/ration3 ,,fig4 #ac4--;,a ne$le depresses ! surface :5 float+4 ,! surface ( wat] acts z if cov]$ by a film :i* coh]es m /rongly ?an ! wat] b5ea? x4 ,?is is %[n by ! fact t a /eel ne$le or a ?9 /rip ( metal may be float$ ^u ! surface ( wat]4 ,x is support$ by ! surface film4 7,see ,fig4 #ac47 ,if ! film breaks ! ne$le s9ks4 ,?is film also supports ! little wat] bugs se5 runn+ ov] ! surface ( a quiet pond 9 summ]4 ,! surface film is /rong] 9 "s liquids ?an 9 o!rs4 ,?is may be %[n by tak+ wat]1 color$ s t x c be se51 plac+ a ?9 lay] ( x on a :ite surface & dropp+ alcohol ^u x4 ,:]ev] ! alcohol drops1 ! wat] is se5 to pull away f x1 leav+ a b>e space ov] :i* ! alcohol has be5 spread4 ,?is indicates t ! alcohol has ! weak] film4 ,! film ( greasy b5z9e is /rong] ?an ! film ( ! pure mat]ial4 ,if "o wi%es to remove a grease spot & places pure b5z9e at ! c5t] ( ! spot1 ! /rong] film ( ! greasy liquid w pull away f ! pure b5z9e1 & spread out1 mak+ a l>g] spot ?an be=e1 :ile if pure b5z9e is plac$ ar\nd ! grease spot1 ! greasy liquid at ! c5t] pulls away f ! pure b5z9e1 draw+ m & m to ! c5t]1 :]e x may be wip$ up & ! grease entirely remov$4 ,illu/ration3 ,,fig4 #ad4--,! molecule at ,a is held diff]5tly f "o )9 ! liquid4 #bc4 ,explanation ( ! ,surface ,film4--,b5ea? ! surface ( a liquid ea* molecule is attract$ by all ! o!r molecules ar\nd x4 ,x is attract$ equally 9 all directions4 ,consequ5tly ! int]ior molecules move v easily ov] ea* o!r 9 any direction4 ,a molecule at ! surface1 z at ,a1 ,fig4 #ad1 is n attract$ upw>d by o!r liquid molecules4 ,its fre$om ( motion is !reby h9d]$ ) ! result t a molecule at ! surface behaves diff]5tly f "o b5ea? ! surface4 ,! surface molecules act z if !y =m an ela/ic sk9 or membrane ^u ! liquid surface4 ,illu/ration3 ,,fig4 #ae4--;,capill>y attraction 9 tubes4 #bd4 ,capill>ity4--,a /rik+ action ( ! surface film ( a liquid is se5 9 ! rise ( liquids 9 tubes ( small bore :5 ! liquid wets !m4 ,if ! liquid does n wet ! tube1 z :5 m]cury is plac$ 9 glass1 ! liquid is depress$4 ,x is f\nd 9 g5]al t3 ,liquids rise 9 capill>y tubes :5 !y wet !m & are depress$ 9 tubes :i* !y d n wet2 ! small] ! diamet] ( ! tube ! great] ! *ange ( level4 7,see ,fig4 #ae47 ,?is action is expla9$ z foll[s3 ,! molecules ( a liquid h an attraction = ea* o!r & also = ! sides ( a tube4 ,! =m] is call$ cohesion = itself1 ! latt] is call$ adhesion = ! sides ( ! conta9+ vessel4 ,if ! cohesion = itself is great] ?an ! adhesion = ! side ( ! conta9+ vessel1 ! liquid is pull$ away f ! side & is depress$4 ,if ! adhesion is great]1 ! liquid is elevat$4 ,?is action is call$ capill>y action f ! ,lat9 ^w 7capillus7 signify+ hair1 s9ce x %[s be/ 9 f9e hairlike tubes4 ,!re are _m common illu/rations ( capill>y action3 oil ris+ 9 a wick2 wat] ris+ 9 a t[el or ?r\gh clo!s2 ink 9 a blott]1 etc4 ,! m9ute spaces betwe5 ! fib]s compos+ ^! objects act z f9e tubes4 ,if clo? is treat$ ) a prep>ation :i* prev5ts wat] f adh]+ to its fib]s1 ! mat]ial w n be wet :5 wat] is p\r$ ^u x1 because ! wat] w n run 9 betwe5 ! fib]s2 a surface film spreads ov] ! clo? s t no wat] ent]s x4 ,crav5ette clo? has be5 treat$ 9 ?is way & h5ce is wat]pro(4 ,! action ( ?is film may be %[n by ! foll[+ exp]im5t4 ,dip a sieve ( f9e copp] gauze 9 melt$ p>aff91 ?us coat+ ea* wire s t wat] w n adh]e to x4 ,wat] may n[ be p\r$ into ! sieve1 if a piece ( pap] is fir/ laid 9 x to break ! =ce ( ! wat]4 ,on c>efully remov+ ! pap] ! surface film ( ! wat] w prev5t ! passage ( ! wat] ?r\gh ! sieve4 #be4 ,capill>y ,action 9 ,soils4--,! di/ribution ( moi/ure 9 ! soil dep5ds l>gely ^u capill>y action4 ,:5 ! soil is compact ! m9ute spaces betwe5 ! soil p>ticles act z capill>y tubes1 ?us aid+ ! wat] to rise to ! surface4 ,z ! wat] evaporates f ! surface m ( x rises by capill>y action f ! damp] soil bel[4 ,keep+ ! soil loose by cultivation1 makes ! spaces betwe5 ! p>ticles too l>ge = mu* capill>y action1 ?us ! moi/ure is l>gely prev5t$ f ris+ to ! surface4 ,9 ! semi-arid regions ( ! ,we/ dry f>m+ is successfully practis$4 ,?is consi/s 9 keep+ ! surface cov]$ ) a du/ mul* produc$ by frequ5t cultivation4 ,9 ?is way ! moi/ure is kept bel[ ! surface1 :]e x c be utiliz$ dur+ ! hot dry summ] by ! roots ( gr[+ plants4 ,important ,topics #a4 ,attractive =ces betwe5 liquid molecules4 #b4 ,cohesion 7l molecules72 adhesion 7unlike molecules74 #c4 ,special effects ( ?is =ce are classifi$ z 7a7 capill>y action1 & 7b7 surface t5sion4 ,ex]cises #a4 ,:at evid5ce ( capill>y action h y se5 outside ( ! laboratory8 #b4 ,:at is ! explanation = capill>y action8 #c4 ,:]e are surface films f\nd8 #d4 ,:at are ?ree common effects ( surface films8 #e4 ,expla9 :y crav5ette clo? %$s wat]4 #f4 ,if a circul> glass disc #aj cm4 9 diamet] requires #ej grams ( =ce to draw x f ! wat]1 :at is ! cohesion ( wat] p] squ>e c5timet]8 #g4 ,:at is ! weight 9 grams ( #a ccm4 ( wat]8 ( a lit] ( wat]8 #h4 ,"n five examples ( adhesion to be f\nd 9 y\r home4 #i4 ,"u :at conditions w a liquid wet a solid & spread ov] x8 #aj4 ,:5 w x =m 9 drops on ! surface8 #aa4 ,expla9 ! prop] proc$ure = remov+ a grease spot ) b5z9e4 #ab4 ,:at diff]5ce is !re betwe5 a liquid & a fluid8 #ac4 ,:y _c a soap bubble be bl[n f pure wat]8 #ad4 ,:i* are l>g]1 ! molecules ( /eam or ^? ( wat]8 ,:y8 #ae4 ,:y is ! gr\nd likely to be damp "u a /one or bo>d :5 x is dry all ar\nd8 #af4 ,:y does any liquid 9 fall+ ?r\gh ! air assume ! globule =m8 #ag4 ,give ?ree examples ( capill>y attraction f\nd 9 ! home4 ,?ree out ( doors4 #ah4 ,:y does cultivation ( ! soil prev5t rapid evaporation ( wat] f ! gr\nd8 7#d7 ,,evid5ces ,,( ,,molecul> ,,=ces ,,9 ,,liquids ,,& ,,solids #bf4 ,solutions4--,a cry/al ( potassium p]manganate is plac$ 9 a lit] ( wat]4 ,x soon dissolves & on %ak+ ! flask ea* portion ( ! liquid is se5 to be color$ r$4 ,! dissolv+ ( ! p]manganate is an illu/ration ( ! attraction ( ! molecules ( wat] = ! molecules ( ! p]manganate4 ,we are famili> ) ?is action 9 ! season+ ( food ) salt & sweet5+ ) sug>4 ,wat] w dissolve _m sub/ances1 b 9 v>y+ degrees1 i4e41 ( "s x w dissolve mu*1 ( o!rs1 little1 & "s n at all4 ,fur!r1 diff]5t liquids h diff]5t solv5t p[]s4 ,alcohol w dissolve res9 & %ellac1 b x w n dissolve gum arabic1 :i* is soluble 9 wat]4 ,b5z9e dissolves grease4 ,beeswax is n dissolv$ by wat]1 alcohol or b5z9e1 b is soluble 9 turp5t9e4 ,x is f\nd t ! temp]ature ( ! liquid has a m>k$ effect ^u ! am\nt ( sub/ance t w dissolve4 ,?is is an indication t ! motions ( ! molecules are effective 9 solution4 ,x appe>s t dissolv+ a solid is 9 "s respects simil> to evaporation1 & j z at high] temp]atures m ( ! liquid evaporates1 because m ( ! molecules w escape f ! liquid into ! air above1 s at high] temp]atures1 m molecules ( a solid w deta* !mselves ?r\gh great] vibration & w move into ! liquid4 ,fur!r1 j z an evaporat+ liquid may saturate ! space above x s t any escape ( molecules is balanc$ by ^? return+1 s ) a dissolv+ solid1 ! liquid may become saturat$ s t ! solution ( m ( ! solid is balanc$ by ! return ( ! molecules f ! liquid to ! solid condition4 #bg4 ,cry/als & ,cry/allization4--,?is return f ! liquid to ! solid /ate1 ( molecules t are 9 solution1 is especially noticeable :5 ! solution is cool+ or evaporat+ & h5ce is los+ its capacity to hold s mu* ( ! solid4 ,on return+ to ! solid1 ! molecules atta* !mselves 9 a def9ite mann] to ! solid portion1 build+ up regul> solid =ms4 ,^! regul> =ms are cry/als4 ,! action t =ms !m is call$ cry/allization4 ,ea* sub/ance seems to h its own peculi> =m ( cry/al due to ! mann] 9 :i* ! molecules atta* !mselves to ^? previ\sly 9 place4 ,! l>ge/ & mo/ symmetrical cry/als are ^? 9 :i* ! molecules are deposit$ sl[ly ) no di/urbance ( ! liquid4 ,beautiful cry/als ( alum may be obta9$ by dissolv+ #be g4 ( alum 9 #ej ccm4 ( hot wat]1 hang+ two or ?ree ?reads 9 ! solution & lett+ x /& ov] night4 ,! ?read fib]s provide a f\ndation ^u :i* cry/als gr[4 ,:5 a solution ( a solid evaporates1 ! molecules ( ! liquid escape z a gas1 ! molecules ( ! solid rema9 accumulat+ z cry/als4 ,?is pr9ciple has _m uses3 7a7 sea wat] is purifi$ by evaporat+ ! wat] & cond5s+ ! vapor1 :i* ( c\rse =ms pure wat]4 7b7 wat] is =c$ d[n to salt b$s :]e x dissolves ! salt4 ,! br9e is !n rais$ & evaporat$1 leav+ ! salt 9 ! evaporat+ pans4 #bh4 ,absorption ( ,gases by ,solids & ,liquids4--,if a piece ( heat$ *>coal is plac$ 9 a te/-tube conta9+ ammonia gas1 inv]t$ 9 m]cury1 ! ammonia is se5 to disappe>1 ! m]cury ris+ to take its place4 ,! ammonia has be5 absorb$ by ! *>coal1 ! gas molecules cl++ closely to ! solid4 ,! *>coal be+ v por\s pres5ts a l>ge surface to ! action ( ! gas4 ,?is exp]im5t indicates t attraction exi/s betwe5 gas molecules & o!r molecules4 ,_m por\s sub/ances h ?is p[] ( absorb+ gases4 ,we h all notic$ t butt] has its flavor affect$ by sub/ances plac$ ne> x4 ,t liquids absorb gases is %[n by sl[ly heat+ cold wat] 9 a beak]4 ,small bubbles ( air =m on ! sides & rise be=e ! boil+ po9t is rea*$4 ,ammonia gas is readily absorb$ 9 wat]1 ! bubbles disappe>+ almo/ z soon z !y escape into ! wat] f ! end ( ! deliv]y tube4 ,h\sehold ammonia is simply a solution ( ammonia gas 9 wat]4 ,on w>m+ ! solution ( ammonia ! gas beg9s to pass (f2 ?us1 w>m+ a liquid t5ds to drive (f any gas dissolv$ 9 x4 ,soda wat] is made by =c+ c>bon dioxide gas into wat] "u /rong pressure4 ,:5 plac$ 9 a vessel op5 to ! air ! pressure is less5$ & "p ( ! gas escapes4 ,! dissolv$ gas gives ! *>act]i/ic ta/e to ! bev]age4 ,important ,topics #a4 ,! solution ( solids is increas$ by heat+4 #b4 ,! solution ( gases is decreas$ by heat+4 #c4 ,pressure increases ! quantity ( gas t c be dissolv$ 9 a liquid4 #d4 ,! attraction 7cohesion7 ( molecules ( a dissolv$ solid = ea* o!r is %[n by cry/allization4 ,ex]cises #a4 ,h[ d fi% obta9 oxyg5 = brea?+8 #b4 ,:y does w>m+ wat] enable x to dissolve m ( a salt8 #c4 ,:y does w>m+ wat] less5 ! am\nt ( a gas t w /ay 9 solution8 #d4 ,w wat] absorb gases ( /rong odor8 ,h[ d y "k8 #e4 ,"n ?ree solv5ts4 ,give a use = ea*4 #f4 ,:at liquids usually conta9 gases 9 solution8 ,"n "s uses = ^! dissolv$ gases4 #g4 ,:at is ! weight ( a cubic met] ( wat]8 #h4 ,"n ?ree sub/ances obta9$ by cry/allization4 #i4 ,h[ is maple sug> obta9$8 #aj4 ,"n five cry/all9e sub/ances4 7#e7 ,,evid5ce ,,( ,,molecul> ,,=ces ,,9 ,,solids #bi4 ,diff]5ces betwe5 ,solids & ,gases4--,9 /udy+ gases1 x is se5 t !y behave z if !y 7 compos$ ( small p>ticles 9 rapid motion1 cont9ually /rik+ & reb\nd+1 & sep>at+ to fill any space into :i* !y are releas$4 ,?is action indicates t !re is practically no attractive =ce betwe5 su* molecules4 ,betwe5 ! molecules ( a solid1 h[ev]1 ! =ces ( attraction are /rong1 z is %[n by ! fact t a solid (t5 requires a great =ce to pull x ap>t2 "s1 z /eel & iron1 %[ ?is prop]ty 9 a sup]lative degree1 a high-grade /eel rod #a cm4 9 diamet] requir+ ne>ly #i tons to pull x ap>t4 ,te/s %[ t ! break+ /r5g?s ( su* rods are directly proportional to _! areas ( cross-section4 ,t is1 twice ! area has twice ! break+ /r5g?4 ,illu/ration3 ,,fig4 #af4--;,ela/icity ( b5d+4 #cj4 ,ela/icity4--,fully z important z a k ( ! break+ /r5g?s ( solids1 is ! k ( :at happ5s :5 ! =ces us$ are n great en\gh to break ! rods or wires4 ,take a wood5 rod 7z a met] /ick7 & clamp "o end to ! table top1 z 9 ,fig4 #af4 ,at ! o!r end hang a weight4 ,fa/5 a wire to ?is end s t x projects out 9 front ( a scale4 ,add successively sev]al equal weights & note ! position ( ! wire ea* "t4 ,remove ! weights 9 ord]1 not+ ! positions z be=e4 ,! rod w probably return to ! fir/ position4 ,?is simple exp]im5t illu/rates a *>act]i/ic ( solids3 t ( *ang+ %ape :5 =ce is appli$ & ( return+ to ! orig9al %ape :5 ! =ce is remov$4 ,?is prop]ty is call$ ela/icity4 ,te/s ( ela/icity are made by subject+ wire ( diff]5t mat]ials b ( ! same dim5sions to ! same t5sion4 ,! "o *ang+ lea/ is said to h ! greate/ ela/ic =ce or ela/icity4 ,if great] =ces are appli$ to ! wire & !n remov$1 "o w f9ally be f\nd t w p]man5tly /ret* ! wire s t x w n return exactly to ! =m] l5g?4 ,! wire has n[ pass$ its ela/ic limit & has be5 p]man5tly /ret*$4 ,j z !re are great diff]5ces betwe5 ! ela/ic =ces ( diff]5t sub/ances1 s !re are great diff]5ces 9 ! limits ( ela/icity4 ,9 "s sub/ances ! limit is rea*$ ) slight di/ortion1 :ile o!rs are p]fectly ela/ic ev5 :5 greatly /ret*$4 ,india rubb] is an example ( a body hav+ p]fect ela/icity ?r\gh wide limits4 ,glass has great ela/ic =ce b its limit ( ela/icity is soon rea*$4 ,sub/ances l ,india rubb] may be said to h great /ret*ability1 b little ela/ic =ce4 ,9 physics1 ela/icity ref]s to ! ela/ic =ce r ?an to ability to endure /ret*+4 #ca4 ,k9ds ( ,ela/icity4--,ela/icity may be %[n 9 f\r ways3 compression1 b5d+ or flexure1 ext5sion or /ret*+1 twi/+ or torsion4 ,! fir/ is illu/rat$ by squeez+ a rubb] eras]1 ! second by an automobile spr+1 ! ?ird by ! /ret*+ ( a rubb] b&1 ! f\r? by ! twi/+ & untwi/+ ( a /r+ by :i* a weight is susp5d$4 ,!re are two k9ds ( ela/icity3 7#a7 ela/icity ( =m or %ape2 7#b7 ela/icity ( volume4 ,gases & liquids possess ela/icity ( volume1 b n ( %ape1 :ile solids may h bo? k9ds4 ,gases & liquids are p]fectly ela/ic because no matt] h[ great pressure may be appli$1 z soon z ! pressure is remov$ !y rega9 _! =m] volume4 ,no solid possesses p]fect ela/icity1 because soon] or lat] ! limit ( ela/icity w be rea*$4 #cb4 ,hooke's ,law4,a--,on exam9+ ! successive movem5ts ( ! end ( ! rod 9 ,art4 #cj1 we f9d t !y are approximately equal4 ,c>efully conduct$ exp]im5ts ^u ! ela/icity ( bodies h %[n t ! *anges 9 %ape are directly proportional to ! =ces appli$1 provid$ t ! limit ( ela/icity is n rea*$4 ,?is relation1 discov]$ by ,rob]t ,hooke1 is sometimes express$ z foll[s3 ,)9 ! limits ( p]fect ela/icity1 all *anges ( size or %ape are directly proportional to ! =ces produc+ !m4 ,a ,a law is a /atem5t ( a con/ant mode ( behavior4 ,x is (t5 express$ 9 ma!matical language4 #cc4 ,molecul> ,=ces & ,molecul> ,motions4--,if a solid is compress$1 on releas+ ! pressure ! body rega9s its =m] %ape if x has n be5 compress$ too f>4 ,?is indicates t at a giv5 temp]ature ! molecules ( a solid t5d to rema9 at a fix$ di/ance f ea* o!r1 & resi/ any attempt to decrease or increase ?is di/ance4 ,?is raises ! "q1 ,:y does n ! cohesion pull ! molecules tightly toge!r s t compression w\ld be impossible8 ,! reason is t heat affects ! size ( solid bodies4 ,on l[]+ ! temp]ature1 bodies d contract1 = z soon z ! temp]ature is l[]$ ! vibration ( ! molecule is less5$4 ,on rais+ ! temp]ature ! molecules are pu%$ f>!r ap>t4 ,! size ( a body1 !n1 is ! result ( a balance ( oppos+ =ces4 ,! attractive =ce betwe5 ! molecules pull+ !m toge!r is cohesion1 :ile ! =ce :i* pu%es !m ap>t is due to ! motions ( ! molecules4 ,rais+ ! temp]ature & ?us increas+ ! motion causes expansion2 l[]+ ! temp]ature decreases ! molecul> motion & s causes contraction4 ,if an outside =ce tries to pull ! body ap>t or to compress x ?is *ange ( size is resi/$ by ei!r cohesion or molecul> motion4 #cd4 ,prop]ties ( ,matt]4--,_m diff]5ces 9 ! physical prop]ties ( solids are due to diff]5ces betwe5 ! cohesive =ce ( diff]5t k9ds ( molecules4 ,9 "s sub/ances1 ! attraction is su* t !y may be roll$ out 9 v ?9 %eets4 ,gold is ! be/ example ( ?is1 %eets be+ =m$ #a_/cjj1jjj ( an in* ?ick4 ,?is prop]ty is call$ malleability4 ,9 o!r sub/ances ! cohesion p]mits x to be drawn out into f9e ?reads or wire4 ,glass & qu>tz are examples ( ?is4 ,?is prop]ty is call$ ductility4 ,9 "s1 ! cohesion makes ! sub/ance excessively h>d1 s t x is difficult to "w or scrat* its surface4 ,! diamond is ! h>de/ sub/ance kn[n4 ,"s sub/ances are t\gh1 o!rs brittle4 ,^! are te/$ by ! ability to )/& sudd5 %ocks z ! bl[ ( a hamm]4 ,important ,topics #a4 ,molecul> =ces 9 solids2 7a7 adhesion1 7b7 cohesion4 #b4 ,ela/icity1 ,hooke's ,law4 #c4 ,contraction on cool+4 #d4 ,malleability1 ductility1 h>dness1 brittl5ess1 etc4 ,ex]cises #a4 ,give an illu/ration ( ,hooke's ,law f y\r own exp]i5ce4 #b4 ,:at devices make use ( x8 #c4 ,d solids evaporate4 ,give reasons4 #d4 ,:5 iron is weld$1 is cohesion or adhesion act+8 #e4 ,:5 a t9 bas9 is sold]$1 is cohesion or adhesion act+8 #f4 ,sometimes a spr+ is made m ela/ic by temp]+ & made s(t by anneal+4 ,look up ! two t]ms4 ,h[ is ea* accompli%$8 #g4 ,review ! def9itions3 solid1 liquid1 & gas4 ,:y d ^! def9itions mean m to y n[ ?an =m]ly8 #h4 ,if a wire is /ret*$ #j4c cm4 on apply+ #d kg4 ( =ce1 :at =ce w /ret* x #j4ge cm8 ,expla94 #i4 ,h[ long w x take "u ord9>y conditions = a gas molecule to cross a room8 ,give reasons = y\r answ]4 #aj4 ,:at is meant by ! ela/ic limit ( a body8 #aa4 ,)\t rea*+ ! ela/ic limit1 if a beam is depress$ #d mm4 "u a load ( #fj kg41 :at w be ! depression "u a load ( #djj kg48 ,( #fjj kg48 #ab4 ,"n ?ree sub/ances t possess ela/icity ( volume4 #ac4 ,give ?ree examples ( ea*2 ela/icity ( 7#a7 compression1 7#b7 /ret*+1 7#c7 torsion1 7#d7 flexure4 ,review ,outl9e3 ,introduction & ,molecules ,physics2 def9ition1 topics consid]$1 physical & *emical *anges4 ,sci5ce2 hypo!sis1 !ory1 law4 ,k2 common1 sci5tific4 ,matt]2 ?ree /ates1 molecul> !ory4 ,mass1 weight1 volume4 ,metric sy/em2 units1 tables1 equival5ts1 advantages4 ,evid5ces ( molecul> motions2 gases 7#c71 liquids 7#e71 solids 7#c74 ,evid5ces ( molecul> =ces2 liquids 7#c71 solids 7_m7 special prop]ties su* z3 ela/icity1 t5acity1 ductility1 h>dness1 etc4 ,hooke's law2 applications4 ,,*apt] ,,iii ,,me*anics ,,( ,,liquids 7#a7 ,,! ,,gravity ,,pressure ,,( ,,liquids #ce4 ,pressure ( ,liquids aga9/ ,surfaces4--,! sight ( a great %ip1 p]haps built ( iron & float+ on wat]1 causes "o to wond] at ! =ce t supports x4 ,?is same =ce is notic$ :5 "o pu%es a light body1 z a cork1 "u wat]4 ,x is q evid5t 9 su* a case t a =ce exi/s suffici5t to ov]come ! weight ( ! cork s t x t5ds to rise to ! surface4 ,ev5 ! weight ( our bodies is s f> support$ by wat] t _m p]sons c float4 ,illu/ration3 ,,fig4 #ag4--,wat] =ces ! c>d aga9/ ! *imney4 ,! foll[+ exp]im5t provides a means ( te/+ ?is =ce3 ,if an empty c is pu%$ d[n into wat]1 we feel at once ! =ce ( ! liquid act+ aga9/ ! object & t5d+ to pu% x upw>d4 ,x may be notic$ also t s long z ! c is n completely subm]g$ ! deep] ! c is pu%$ into ! wat] ! great] is ! upw>d =ce ex]t$ by ! liquid4 ,we may te/ ?is action 9 v>i\s ways3 a simple way is to take a cyl9drical lamp *imney1 press a c>d aga9/ its l[] end & place x 9 ! wat] 9 a v]tical position4 ,! =ce ( ! wat] w hold ! c>d firmly aga9/ ! end ( ! *imney4 7,see ,fig4 #ag47 ,! am\nt ( =ce may be te/$ by dropp+ %ot into ! tube until ! c>d drops (f4 ,at great] dep?s m %ot w be requir$1 %[+ t ! =ce ( ! wat] increases ) ! dep?4 ,or "o may p\r wat] into ! *imney4 ,x w !n be f\nd t ! c>d does n drop until ! level ( ! wat] inside ! *imney is ! same z on ! outside4 ,t is1 be=e ! c>d w fall (f1 ! wat] mu/ /& z high )9 ! *imney z )\t no matt] to :at dep? ! l[] end ( ! *imney is ?ru/ bel[ ! surface ( ! wat]4 #cf4 ,law ( ,liquid ,pressure4--,z !re is twice z mu* wat] or %ot 9 ! *imney :5 x is fill$ to a dep? ( #aj cm4 z !re is :5 x is fill$ to a dep? ( #e cm4 ! =ce ( ! wat] upw>d on ! bottom mu/ be twice z great at a dep? ( #aj cm4 z at a dep? ( #e cm4 ,s9ce ?is reason+ w hold good = a comp>ison ( =ces at any two dep?s1 we h ! law3 ,! pressure ex]t$ by a liquid is directly proportional to ! dep?4 ,! am\nt ( ?is =ce may be comput$ z foll[s3 ,fir/1 ! c>d /ays on ! end ( ! tube until ! weight ( wat] f above equals ! =ce ( ! wat] f bel[1 & second1 ! c>d rema9s until ! wat] is at ! same height inside ! tube z x is outside4 ,n[ if we f9d ! weight ( wat] at a giv5 dep? 9 ! tube1 we c det]m9e ! =ce ( ! wat] f bel[4 ,if = in/ance ! *imney has an area ( cross-section ( #ab sq4 cm4 & is fill$ ) wat] to a dep? ( #aj cm41 ! volume ( ! wat] conta9$ w be #abj ccm4 ,?is volume ( wat] w weigh #abj g4 ,?is repres5ts !n1 n only ! weight ( ! wat] 9 ! tube1 b also ! =ce ( ! wat] aga9/ ! bottom4 ,9 a simil> way "o may measure ! =ce ( wat] aga9/ any horizontal surface4 #cg4 ,=ce & ,pressure4--,we %\ld n[ di/+ui% betwe5 =ce & pressure4 ,pressure ref]s to ! =ce act+ aga9/ unit area1 :ile =ce ref]s to ! action aga9/ ! :ole surface4 ,?us = example1 ! atmosph]ic pressure is (t5 giv5 z #ae p\nds to ! squ>e in* or z "o kilogram to ! squ>e c5timet]4 ,on ! o!r h&1 ! air may ex]t a =ce ( m ?an #cjj p\nds ^u ea* side ( ! h& ( a man2 or a l>ge %ip may be support$ by ! =ce ( ?\s&s ( tons ex]t$ by wat] aga9/ ! bottom ( ! %ip4 ,9 ! illu/ration1 giv5 9 ,art4 #cf1 ! upw>d =ce ( ! wat] aga9/ ! end ( ! tube at a dep? ( #aj cm4 is comput$ z #abj grams4 ,! pressure at ! same dep? w be #aj grams p] sq4 cm4 ,:at w be ! pressure at a dep? ( #bj cm48 at a dep? ( #ej cm48 ( #ajj cm48 ,comp>e ^! answ]s ) ! law ( liquid pressure 9 ,art4 #cf4 #ch4 ,d5sity4--,if o!r liquids1 z alcohol1 m]cury1 etc41 7 9 ! j>1 ! *imney w\ld ne$ fill+ to ! same level outside1 ) ! same liquid1 be=e ! c>d w\ld fall (f4 ,?is br+s 9 a factor t 0 n consid]$ be=e1 t ( ! mass,b ( a cubic c5timet] ( ! liquid4 ,?is is call$ ! d5sity ( ! liquid4 ,alcohol has a d5sity ( #j4h g4 p] cubic c5timet]1 m]cury ( #ac4f g4 p] cubic c5timet]1 :ile wat] has a d5sity ( #a g4 p] cubic c5timet]4 ,b ,! mass ( a body is ! am\nt ( matt] 9 x1 ! weight is ! pull ( ! e>? ^u x4 #ci4 ,liquid ,=ce aga9/ ,any ,surface4--,to f9d ! =ce ex]t$ by a liquid aga9/ a surface we mu/ take into consid]ation ! area ( ! surface1 & ! height & ! d5sity ( ! liquid above ! surface4 ,! foll[+ law1 & ! =mula repres5t+ x1 :i* concisely expresses ! pr9ciple by :i* ! =ce ex]t$ by a liquid aga9/ any surface may be comput$1 %\ld be memoriz$3 ,! =ce :i* a liquid ex]ts aga9/ any surface1 equals ! area ( ! surface1 times its av]age dep? bel[ ! surface ( ! liquid1 times ! weight ( unit volume ( ! liquid4 ,or1 express$ by a =mula1 ,f ,ahd4 ,9 ?is =mula1 ,f /&s = ! =ce :i* a liquid ex]ts aga9/ any surface1 ,a ! area ( ! surface1 h1 = ! av]age dep? 7or height7 ( ! liquid press+ on ! surface1 & d1 = ! weight ( unit volume ( ! liquid4 ,?is is ! fir/ illu/ration 9 ?is text1 ( ! use ( a =mula to repres5t a law4 ,obs]ve h[ accurately & concisely ! law is express$ by ! =mula4 ,:5 ! =mula is employ$1 h[ev]1 we %\ld keep 9 m9d ! law express$ by x4 ,we mu/ rememb] t a liquid presses n only d[nw>d & upw>d b sideways z well1 z we see :5 wat] spurts out ( a hole 9 ! side ( a vessel4 ,exp]im5ts h %[n t at a po9t ! pressure 9 a fluid is ! same 9 all directions1 h5ce ! rule giv5 above may be appli$ to ! pressure ( a liquid aga9/ ! side ( a tank1 or boat1 or o!r object1 provid$ we are accurate 9 det]m9+ ! av]age dep? ( ! liquid2 ,! foll[+ example illu/rates ! use ( ! law4 ,= ,example3 ,if ! ,engli% sy/em is us$1 ! area ( ! surface %\ld be express$ 9 squ>e feet1 ! dep? 9 feet & ! weight ( ! liquid 9 p\nds p] cubic foot4 ,"o cubic foot ( wat] weighs #fb4d lbs4 ,suppose t a box #c ft4 squ>e & #d ft4 deep is full ( wat]4 ,:at =ce w be ex]t$ by ! wat] aga9/ ! bottom & a side8 ,f ! law giv5 above1 ! =ce ( a liquid aga9/ a surface equals ! product ( ! area ( ! surface1 ! dep? ( ! liquid & its weight p] unit volume1 or us+ ! =mula1 ,f ,ahd4 ,to compute ! d[nw>d =ce aga9/ ! bottom we h ! area1 #i1 dep?1 #d1 & ! weight #fb4d lbs4 p] cubic foot4 #i #d #fb4d lbs4 #bbdf4d lbs4 ,to compute ! =ce aga9/ a side1 ! area is #ab1 ! av]age dep? ( wat] on ! side is #b1 ! weight #fb4d1 #ab #b #fb4d lbs4 #adig4f lbs4 ,important ,topics #a4 ,liquids ex]t pressure2 ! great] ! dep? ! great] ! pressure4 #b4 ,diff]5ce betwe5 =ce & pressure4 #c4 ,rules = f9d+ upw>d & horizontal =ce ex]t$ by a liquid4 ,f ,ahd4 #d4 ,weight1 mass1 d5sity4 ,ex]cises #a4 ,:at is ! d5sity ( wat]8 #b4 ,:at =ce is press+ upw>d aga9/ ! bottom ( a flat boat1 if x is #fj ft4 long1 #ae ft4 wide & s9ks to a dep? ( #b ft4 9 ! wat]8 ,:at is ! weight ( ! boat8 #c4 ,if a load$ %ip s9ks 9 ! wat] to an av]age dep? ( #bj ft41 ! area ( ! bottom be+ #fjjj sq4 ft41 :at is ! upw>d =ce ( ! wat]8 ,:at is ! weight ( ! %ip8 #d4 ,if ?is %ip s9ks only #aj ft4 :5 empty1 :at is ! weight ( ! %ip alone8 ,:at 0 ! weight ( ! c>go 9 ,problem #c8 #e4 ,:at is ! liquid =ce aga9/ "o side ( an aqu>ium #aj ft4 long1 #d ft4 deep & full ( wat]8 #f4 ,:at is ! liquid =ce on "o side ( a lit] cube full ( wat]8 ,full ( alcohol8 ,full ( m]cury8 ,:at =ce is press+ on ! bottom 9 ea* case8 #g4 ,:at dep? ( wat] w produce a pressure ( #a g4 p] squ>e c5timet]8 #aj g4 p] squ>e c5timet]8 #ajjj g4 p] squ>e c5timet]8 #h4 ,:at dep? ( wat] w produce a pressure ( #a lb4 p] squ>e in*8 #aj lbs4 p] squ>e in*8 #ajj lbs4 p] squ>e in*8 #i4 ,:at w be ! =ce aga9/ a v]tical dam-brea/ #cj met]s long1 ! dep? ( ! wat] be+ #aj met]s8 #aj4 ,a trap door ) an area ( #ajj sq4 dcm4 is set 9 ! bottom ( a tank conta9+ wat] #e met]s deep4 ,:at =ce does ! wat] ex]t aga9/ ! trap door8 #aa4 ,:at is ! =ce on ! bottom ( a conical tank1 fill$ ) wat]1 ! bottom ( :i* is #c met]s 9 diamet]1 ! dep? #a4e met]s8 #ab4 ,if alcohol1 d5sity #j4h 7 us$ 9 problem #aa1 :at w\ld be ! =ce8 ,:at w\ld be ! dep? ( alcohol to h ! same =ce on ! bottom z 9 problem #aa8 #ac4 ,:at is ! pressure 9 p\nds p] squ>e in* at a dep? ( #a mile 9 sea wat]1 d5sity #a4jbf grams p] cc48 #ad4 ,f9d ! =ce on ! sides & bottom ( a rectangul> ci/]n fill$ ) wat]1 #bj ft4 long1 #aj ft4 wide1 & #aj ft4 deep8 #ae4 ,f9d ! =ce on ! bottom ( a wat] tank #ad ft4 9 diamet] :5 ! wat] is #ae ft4 deep1 :5 full ( wat]4 #af4 ,f9d ! =ce on "o side ( a ci/]n #h ft4 deep & #aj ft4 squ>e1 :5 full ( wat]4 #ag4 ,f9d ! =ce on a v]tical dam #cjj ft4 long & #aj ft4 high1 :5 full ( wat]4 #ah4 ,f9d ! pressure at ! bottom ( ! dam 9 "q #ag4 #ai4 ,:y are dams made ?ick] at ! bottom ?an at ! top8 #bj4 ,a %ip draws #bf ft4 ( wat]1 i4e41 its keel is #bf ft4 "u wat]4 ,:at is ! liquid =ce aga9/ a squ>e foot surface ( ! keel8 ,f9d ! pressure on ! bottom4 7#b7 ,,transmission ,,( ,,liquid ,,pressure #dj4 ,pascal's ,pr9ciple4--,liquids ex]t pressure n only due to _! own weight1 b :5 conf9$1 may be made to transmit pressure to consid]able di/ances4 ,?is is a matt] ( common k :]ev] a sy/em ( wat]works ) connections to h\ses is f\nd1 z 9 cities4 ,! transmission ( liquid pressure has a numb] ( important applications4 ,! pr9ciple und]ly+ ea* ( ^! 0 fir/ discov]$ by ,pascal1 a ,fr5* sci5ti/ ( ! sev5te5? c5tury4 ,pascal's ,pr9ciple1 z x is call$1 may be illu/rat$ z foll[s3 ,suppose a vessel ( ! %ape %[n 9 ,fig4 #ah1 ! upp] "p ( :i* we may assume has an area ( #a sq4 cm41 is fill$ ) wat] up to ! level ,,ab4 ,a pressure w be ex]t$ ^u ea* squ>e c5timet] ( area dep5d+ ^u ! dep?4 ,suppose t ! height ( ,,ab above ,,cd is #aj cm41 !n ! =ce ^u #a sq4 cm4 ( ,,cd is #aj g41 or if ! area ( ,,cd is #af sq4 cm41 x receives a =ce ( #afj g4 ,illu/ration3 ,,fig4 #ah4--,! =ce increases ) ! dep?4 ,if n[ a cubic c5timet] ( wat] be p\r$ ^u ,,ab x w raise ! level #a cm41 or ! head ( wat] ex]t+ pressure ^u ,,cd becomes #aa cm41 or ! total =ce 9 ,,cd is #afaa g41 i4e41 ea* squ>e c5timet] ( ,,cd receives an additional =ce ( #a g4 ,h5ce ! =ce ex]t$ on a unit area at ,,ab is transmitt$ to e unit area )9 ! vessel4 ,! usual =m 9 :i* ?is law is express$ is z foll[s3 ,pressure appli$ to any "p ( a conf9$ liquid is transmitt$ un*ang$1 9 all directions1 & adds ! same =ce to all equal surfaces 9 contact ) ! liquid4 ,illu/ration3 ,,fig4 #ai4--,! =ce is proportional to ! area4 ,! importance ( ?is pr9ciple1 z ,pascal himself po9t$ out1 lies 9 ! fact t by its aid we are able to ex]t a great =ce ^u a l>ge area by apply+ a small =ce ^u a small area ( a conf9$ liquid1 bo? areas be+ 9 contact ) ! same liquid4 ,?us 9 ,fig4 #ai if ! area ( ! surface ,,cd is #bjjj times ! area ( ! surface ,,ab1 !n #a lb4 appli$ to ! liquid on ,,ab w ex]t or su/a9 a =ce ( #bjjj lbs4 on ,,cd4 #da4 ,hydraulic ,press4--,an important application ( ,pascal's pr9ciple is ! hydraulic press4 ,see ,fig4 #bj4 ,x is us$ = _m purposes :]e great =ce is requir$1 z 9 press+ pap] or clo?1 extract+ oil f se$s1 lift+ heavy objects1 etc4 ,_m high s*ool pupils h be5 seat$ 9 a hydraulic *air us$ by a d5ti/ or b>b]4 ,?is *air is a modifi$ hydraulic press4 ,illu/ration3 ,,fig4 #bj4--;,cross-section ( a hydraulic press4 ,! hydraulic press conta9s two movable pi/ons1 ,p & p 7see ,fig4 #bj74 ,! l>g] ( ^!1 ,p1 has a cross-sectional area t may be #ajj or #ajjj times t ( ! small]4 ,! small] "o is mov$ up & d[n by a lev]2 on ea* up/roke1 liquid is drawn 9 f a res]voir1 :ile ea* d[n-/roke =ces "s ( ! liquid into ! space ab\t ! l>ge pi/on4 ,valves at ,v & ,v prev5t ! return ( ! liquid4 ,if ! area ( ,p is #a1jjj times t ( p1 !n ! =ce ex]t$ by ,p is #ajjj times ! =ce employ$ 9 mov+ p4 ,on ! o!r h&1 s9ce ! liquid mov$ by ! small pi/on is di/ribut$ ov] ! area ( ! l>ge "o1 ! latt] w move only #a_/ajjj z f> z does ! small pi/on4 ,! relation betwe5 ! motions ( ! two pi/ons & ! =ces ex]t$ by !m may be /at$ concisely z foll[s3 ,! motions ( ! two pi/ons ( ! hydraulic press are inv]sely proportional to ! =ces ex]t$ by !m4 ,! cross-sectional areas ( ! two pi/ons are1 on ! o!r h&1 directly proportional to ! =ces ex]t$ by !m4 ,an application ( ,pascal's pr9ciple (t5 employ$ 9 cities is ! hydraulic elevator4 ,9 ?is device a long plung] or pi/on ext5ds d[nw>d f ! elevator c> into a cyl9d] sunk into ! e>?1 sometimes to a dep? ( #cjj ft4 ,wat] =c$ into ?is cyl9d] pu%es ! pi/on upw>d & :5 ! wat] is releas$ f ! cyl9d] ! pi/on desc5ds4 ,fig4 #ba repres5ts ano!r =m ( hydraulic elevator1 :]e ! cyl9d] & pi/on are at "o side ( ! elevator %aft4 ,9 ?is type1 to raise ! elevator1 wat] is admitt$ to ! cyl9d] pu%+ ! pi/on d[nw>d4 #db4 ,artesian ,wells4--,sometimes a por\s /ratum conta9+ wat] 9 ! e>?'s cru/ is incl9$4 ,!n if !re are imp]vi\s /rata 7see ,fig4 #bb71 bo? above & bel[ ! wat]-be>+ "o1 & ! latt] comes to ! surface s t ra9 may fill x1 a well sunk to ! wat]-be>+ /ratum at a po9t :]e x is bel[ ! surface w usually give an artesian well1 t is1 "o 9 :i* ! wat] rises to or above ! surface4 ,_m are f\nd 9 ! ,unit$ ,/ates4 ,illu/ration3 ,,fig4 #ba4--;,a hydraulic freight elevator4 ,illu/ration3 ,,fig4 #bb4--;,conditions produc+ an artesian well4 ,illu/ration3 ,,fig4 #bc4--;,a /&pipe4 #dc4 ,/&pipes & ,air ,cu%ions4--,_m :o h liv$ 9 cities :]e wat] is pump$ into h\ses "u pressure "k t ! wat] pressure is *ang$ :5 sev]al faucets are op5$ at ! same "t4 ,aga91 if sev]al p]sons are us+ a hose = spr9kl+1 ! pressure may be less5$ s z to be insuffici5t to =ce ! wat] above ! fir/ floor4 ,9 ord] to all[ = ^! *anges "s flexibility or spr+ mu/ be introduc$ some:]e into ! wat]-pipe sy/em4 ,wat] is ne>ly incompressible & if no means 7 employ$ to take c>e ( ! pressure *anges1 ! sudd5 /opp+ & />t+ ( ! fl[ w\ld cause s]i\s j>s & />t leaks 9 ! pipes4 ,two common devices = controll+ sudd5 *anges 9 ! wat] pressure are ! /&pipe & ! air cu%ion4 ,! /&pipe is simply a l>ge v]tical tube connect$ to ! wat] ma9s f :i* & into :i* wat] readily fl[s4 ,:5 _m faucets are op5$ ! wat] l[]s2 :5 mo/ faucets are clos$ ! wat] rises1 giv+ a simple automatic control ( ! surplus wat] & a supply ( wat] = a %ort "t dur+ a %ut-d[n ( ! pumps4 ,/&pipes are (t5 us$ 9 t[ns & small cities4 ,fig4 #bc repres5ts ! /&pipe at ,j]ome1 ,idaho4 ,! air cu%ion 7,fig4 #bd7 is a metal pipe or dome fill$ ) air atta*$ to a wat] pipe :]e sudd5 *anges 9 pressure are to be controll$4 ,at _m faucets 9 a city wat] sy/em su* an air cu%ion is employ$4 ,x conta9s air2 ?is1 unlike wat]1 is easily compressible & ! conf9$ air :5 ! tap is sudd5ly clos$ receives & *ecks gradually ! ru% ( wat] 9 ! pipe4 ,ev5 ) an air cu%ion1 ! p\nd ( ! wat] 9 ! pipe :5 a tap is sudd5ly clos$ is (t5 he>d4 ,if air cu%ions 7 n provid$1 ! wat] hamm] w\ld frequ5tly crack or break ! pipes4 ,illu/ration3 ,,fig4 #bd4--,! %ort pipe above ! faucet conta9s air =m+ an air cu%ion4 ,important ,topics #a4 ,pascal's law4 #b4 ,hydraulic press4 #c4 ,artesian wells4 #d4 ,/&pipes & air cu%ions4 ,ex]cises #a4 ,:]e h y se5 an air cu%ion8 ,describe x & its use4 #b4 ,:]e h y se5 an hydraulic press8 ,:y & h[ us$8 #c4 ,:]e h y se5 hydraulic elevators8 ,:at moves !m8 #d4 ,:]e d y "k ( liquids "u pressure8 ,?ree examples4 #e4 ,:at is ! pressure 9 wat] at a dep? ( #aejj cm4 ,express 9 grams p] squ>e c5timet] & 9 kilograms p] squ>e c5timet]4 #f4 ,:at head,c ( wat] is requir$ to give a pressure ( #bjj g4 p] squ>e c5timet]8 #b kg4 p] squ>e c5timet]8 ,c ,head is a t]m us$ to express ! v]tical height ( wat] 9 pipes4 #g4 ,:at pressure w be produc$ by a head ( wat] ( #bj met]s8 #h4 ,if #agbh cu4 94 ( wat] are plac$ 9 a v]tical tube #a sq4 94 9 cross section to :at height w\ld ! wat] rise8 ,x w\ld give h[ _m feet ( head8 #i4 ,:at w\ld ! wat] 9 problem #h weigh8 ,:at pressure w\ld x produce at ! bottom1 9 p\nds p] squ>e in*8 ,f ?is1 compute h[ _m feet ( head ( wat] w produce a pressure ( #a lb4 p] squ>e in*4 #aj4 ,us+ ! result 9 problem #i1 :at head ( wat] w produce a pressure ( #aj lbs4 p] squ>e in*8 #ajj lbs4 p] squ>e in*8 #aa4 ,f ! result 9 #i1 #ajj ft4 ( head ( wat] w produce :at pressure8 #ajjj ft4 ( head8 #ab4 ,if ! diamet] ( ! pump pi/on 9 a hydraulic press is #b cm4 & t ( ! press pi/on #ej cm4 :at w be ! =ce aga9/ ! latt] if ! =m] is pu%$ d[n ) a =ce ( #dj kg48 7#c7 ,,ar*im$es' ,,pr9ciple #dd4 ,a ,body ,support$ by a ,liquid4--,among ! applications ( ! =ce ex]t$ by a liquid ^u a surface1 ,ar*im$es' ,pr9ciple is "o ( ! mo/ important4 ,mo/ p]sons h not$ t a body plac$ 9 wat] is p>tly or :olly support$ by ! =ce ( ! wat] ^u x4 ,a /one held by a cord & l[]$ into wat] is felt to h a "p ( its weight support$1 :ile a piece ( cork or wood is :olly support$ & floats4 ,! human body is almo/ entirely support$ 9 wat]1 9 fact1 _m p c easily float 9 wat]4 ,x 0 ! consid]ation ( ?is fact t l$ ! ,greek philosoph] ,ar*im$es to discov] & /ate ! pr9ciple t describes ! support+ ( a body 9 a liquid4 ,illu/ration3 ,,fig4 #be4--,!oretical pro( ( ,ar*im$es' pr9ciple4 #de4 ,ar*im$es' ,pr9ciple4--,a body imm]s$ 9 a liquid is pu%$ up by a =ce equal to ! weight ( ! liquid t x displaces4 ,! pro( = ?is law is simply demon/rat$4 ,suppose a cube1 abcd1 is imm]s$ 9 wat] 7,fig4 #be74 ,! upw>d =ce on cd is equal to ! weight ( a column ( wat] equal to cdef4 7,see ,art4 #ci47 ,! d[nw>d =ce ^u ! top ( ! cube is equal to ! weight ( ! column ( wat] abef4 ,!n ! net upw>d =ce ^u ! cube1 t is1 ! upw>d =ce ^u ! bottom less ! d[nw>d =ce ^u ! top1 or ! buoyant =ce ex]t$ by ! liquid is exactly equal to ! weight ( ! displac$ wat] abcd4 #df4 ,law ( ,float+ ,bodies4--,?is same reason+ may be appli$ to any liquid & to any body imm]s$ to any dep? bel[ ! surface ( ! liquid4 ,if ! body weighs m ?an ! displac$ liquid x w s9k4 ,if x weighs less ?an ! displac$ liquid x w float or rise 9 ! wat]4 ,a block ( wood rises out ( ! wat] 9 :i* x floats until its own weight j equals ! weight ( ! wat] x displaces4 ,f ?is we h ! law ( float+ bodies4 ,a float+ body displaces its own weight ( ! liquid 9 :i* x floats4 ,illu/ration3 ,,fig4 #bf4--;,a float+ body displaces its own weight ( wat]4 ,to te/ ! law ( float+ bodies1 take a rod ( light wood #a cm4 squ>e & #cj cm4 long 7,fig4 #bf74 ,bore out "o end & fill ! op5+ ) lead & seal ) p>aff9 s t ! rod w float v]tically :5 plac$ 9 wat]4 ,m>k ^u "o side ( ! rod a c5timet] scale1 & dip ! rod 9 hot p>aff9 to make x wat]pro(4 ,n[ f9d ! weight ( ! /ick 9 grams & note ! dep? to :i* x s9ks 9 wat] 9 c5timet]s4 ,compute ! weight ( ! displac$ wat]4 ,x w equal ! weight ( ! rod4 #dg4 ,applications ( ,ar*im$es' ,pr9ciple4 ,!re are num]\s applications ( ,ar*im$es' ,pr9ciple & ! law ( float+ bodies4 7a7 ,to ,f9d ! ,weight ( a ,float+ ,body3 ,problem4--,a boat #bj ft4 long & ) an av]age wid? ( #f ft4 s9ks to an av]age dep? ( #c ft4 9 ! wat]4 ,f9d ! weight ( ! boat4 ,:at weight ( c>go w s9k x to an av]age dep? ( #e ft48 ,solution4--,! volume ( ! wat] displac$ is #bj #f #c cu4 ft4 #cfj cu4 ft4 ,s9ce #a cu4 ft4 ( wat] weighs #fb4d lbs41 #cfj #fb4d lbs4 #bb1dfd lbs41 ! weight ( wat] displac$4 ,by ! law ( float+ bodies ?is is equal to ! weight ( ! boat4 ,:5 load$ ! volume ( wat] displac$ is #bj ft4 #f #e ft4 :i* equal #fjj cu4 ft4 #fjj #fb4d lbs4 #cg1ddj lbs4 ,?is is ! weight ( ! wat] displac$ :5 load$4 #cg1ddj lbs4 - #bb1dfd lbs4 #ad1igf lbs41 ! weight ( ! c>go4 7b7 ,to ,f9d ! ,volume ( an ,imm]s$ ,solid3 ,problem4--,a /one weighs #ahg4b lbs4 9 air & appe>s to weigh #abd4h lbs4 9 wat]4 ,:at is its volume8 ,solution4--#ahg4b lbs4 - #abd4h lbs4 #fb4d lbs41 ! buoyant =ce ( ! wat]4 ,by ,ar*im$es' ,pr9ciple1 ?is equals ! weight ( ! displac$ wat] :i* has a volume ( #a cu4 ft4 :i* is !re=e ! volume ( ! /one4 7c7 ,to ,f9d ! ,d5sity ( a ,body3 ,! d5sity ( a body is def9$ z ! mass ( unit volume4 ,we c easily f9d ! mass ( a body by weigh+ x1 b ! volume is (t5 impossible to obta9 by measurem5ts1 especially ( irregul> solids4 ,ar*im$es' ,pr9ciple1 h[ev]1 provides a me?od ( f9d+ ! volume ( a body accurately by weigh+ x fir/ 9 air & !n 9 wat] 7,fig4 #bg71 ! app>5t loss 9 weight be+ equal to ! weight ( ! displac$ wat]4 ,"o ne$s only to f9d ! volume ( wat] hav+ ! same weight z ! loss ( weight to f9d ! volume ( ! body4 ,if ! metric sy/em is us$1 #a ccm4 ( wat] weighs #a g41 & ! volume is num]ically ! same z ! loss ( weight4 ,illu/ration3 ,,fig4 #bg4--;,a me?od ( weigh+ a body "u wat]4 ,important ,topics #a4 ,ar*im$es' ,pr9ciple4 #b4 ,law ( float+ bodies4 #c4 ,! applications ( ,ar*im$es' ,pr9ciple are to det]m9e 7a7 ! weight ( a float+ body2 7b7 ! volume ( an imm]s$ solid1 & 7c7 ! d5sity ( a body4 ,ex]cises #a4 ,look up ! /ory ( ,ar*im$es & ! cr[n4 ,write a brief acc\nt ( x4 #b4 ,:y is x easi] = a fat man to float 9 wat] ?an = a lean "o8 #c4 ,a fi% weigh+ #a lb4 is plac$ 9 a pail full ( wat]4 ,w ! pail & cont5ts weigh m ?an be=e add+ ! fi%8 ,:y8 #d4 ,:y c a l>ge /one be lift$ m easily :ile "u wat] ?an :5 on ! l&8 #e4 ,:y does ! air bubble 9 a _s level move z "o end ( ! in/rum5t is rais$ or l[]$8 #f4 ,:y does a dead fi% always float8 #g4 ,a %ip is built = use 9 fre% wat]4 ,:at w be ! effect on its wat] l9e :5 pass+ into ! ocean8 #h4 ,:y c small bugs walk on wat] :ile l>ge animals _c8 #i4 ,if an object weigh+ #fb4d lbs4 j floats 9 wat]1 :at weight ( wat] does x displace8 ,:at volume ( wat] is displac$8 ,:at is ! volume ( ! body8 #aj4 ,:at is ! volume ( a man :o j floats 9 wat] if he weighs #abd4h lbs48 ,if he weighs #ahg4b lbs48 #aa4 ,an object weigh+ #ejj g4 j floats 9 wat]4 ,:at is its volume8 ,h[ mu* wat] does a float+ block ( wood displace if x weighs #abe lbs48 #abe g48 #b kg48 #bjjj kg48 #ab4 ,a flat boat #aj #dj ft4 9 size w s9k h[ mu* 9 ! wat] :5 #aj horses ea* weigh+ #abej lbs4 are plac$ on bo>d8 #ac4 ,a %ip #ijj ft4 long & #hj ft4 av]age wid? s9ks to an av]age dep? ( #be ft4 :5 empty & #dj ft4 :5 load$4 ,:at is ! weight ( ! %ip & ( its load8 #ad4 ,w a #ajjj cc4 block s9k or float 9 wat] if x weighs #hjj g48 ,if x weighs #abjj g48 ,expla94 #ae4 ,if a #ajjj cc4 block ( metal weigh+ #abjj g4 is plac$ 9 ! wat] 9 mid ocean :at w become ( x8 #af4 ,prove ,ar*im$es' ,pr9ciple by use ( ! pr9ciples ( liquid pressure4 #ag4 ,an irregul> /one1 d5sity #b4e g4 p] ccm4 displaces #b cu4 ft4 ( wat]4 ,:at is its weight8 ,its app>5t weight 9 wat]8 #ah4 ,w ! dep? to :i* a vessel s9ks 9 wat] *ange z %e sails f ,lake ,ont>io into ! ,atlantic ,ocean8 ,:y8 #ai4 ,if ! d5sity ( sea wat] is #a4jbfi g4 p] cubic c5timet] & t ( ice #j4iah g4 p] ccm41 :at portion ( an iceb]g is above wat]8 #bj4 ,9 draw+ wat] f a well by means ( a bucket1 :y is less =ce us$ :5 x is "u wat] ?an :5 entirely above8 #ba4 ,a /one :i* weighs #cjj lbs4 c be lift$ "u wat] ) a =ce ( #aej lbs4 ,:at is ! volume ( ! /one8 #bb4 ,! av]age d5sity ( ! human body is #a4jg grams p] c4c4 ,h[ mu* wat] w a man :o weighs #aej lbs4 displace :5 div+8 ,h[ mu* :5 float+8 7#d7 ,,d5sity ,,& ,,specific ,,gravity #dh4 ,d5sity4--,! d5sity ( a sub/ance is (t5 us$ z a te/ ( its purity4 ,ar*im$es 9 te/+ ,k+ ,hi]o's cr[n to f9d out if x 7 made ( pure gold det]m9$ fir/ its d5sity4 ,x is by su* te/s t ! purity ( milk1 ( alcohol1 ( gold1 & a great v>iety ( sub/ances is (t5 det]m9$4 ,k ( me?ods ( f9d+ d5sity is ( value to ev]yone & %\ld be includ$ 9 ! education ( e /ud5t4 ,! d5sity ( a sub/ance is ! mass ( unit volume ( ! sub/ance4 ,9 ! metric sy/em1 = example1 ! d5sity ( a sub/ance is ! mass 9 grams p] #a ccm4 ,tak+ wat]1 #a ccm4 weighs #a gr4 or its d5sity is !re=e #a g4 to ! cubic c5timet]4 ,a cubic c5timet] ( alum9ium weighs #b4g g4 ,its d5sity !re=e is #b4g g4 p] ccm4 #di4 ,specific ,gravity4--,specific gravity is ! ratio ( ! weight ( any volume ( a sub/ance to ! weight ( an equal volume ( wat]4 ,its mean+ is n q ! same z t ( d5sity1 s9ce specific gravity is always a ratio1 i4e41 an ab/ract numb]1 z #b4g4 ,d5sity ( a sub/ance is a concrete numb]1 z #b4g grams p] ccm4 ,9 ! metric sy/em ! d5sity ( wat] is "o gram p] cubic c5timet]1 !re=e we h3 ,d5sity 7g4 p] ccm47 7num]ically7 specific gravity4 ,9 ! ,engli% sy/em1 ! d5sity ( wat] is #fb4d p\nds p] cubic foot1 !re=e 9 ?is sy/em we h3 ,d5sity 7lbs4 p] cu4 ft47 7num]ically7 #fb4d sp4 gr4 #ej4 ,me?ods = ,f9d+ ,d5sity & ,specific ,gravity 7a7 ,regul> ,solids4--,solids ( regul> %apes su* z cubes1 sph]es1 etc41 ^: volumes may be readily f\nd by measurem5t1 may be weigh$4 ,! mass divid$ by ! volume gives ! d5sity1 or ,d ,m_/v4 7b7 ,irregul> ,solids4--) ^! ! volume _c be f\nd by measurem5t b may be obta9$ by ,ar*im$es' ,pr9ciple4 ,weigh ! solid fir/ 9 ! air & !n 9 wat]4 ,! app>5t loss ( weight equals ! weight ( ! equal volume ( wat] displac$4 ,f ?is ! volume may be f\nd4 ,& !n ! d5sity equals mass_/volume2 ! specific gravity wt4 9 air _/ wt4 ( equal volume ( wat] wt4 9 air _/ 77wt4 9 air7 - 7wt4 9 wat]77 mass d5sity equals ------2 ! specific gravity volume wt4 9 air wt4 9 air ---------------------------- ----------------------------- wt4 ( equal volume ( wat] 77wt4 9 air7 - 7wt4 9 wat]77 7c7 ,solids ,light] ?an ,wat]4--,?is w require a s9k] to hold ! body "u wat]4 ,weigh ! solid 9 air 7w74 ,weigh ! s9k] 9 wat] 7s74 ,atta* ! s9k] to ! solid & weigh bo? 9 wat] 7w74 ,! specific gravity equals 7wt4 ( solid 9 air7_/7loss 9 wt4 ( solid 9 wat]7 or w_/77w s7 - w7 wt4 ( solid 9 air w --------------------------- or ------------ loss ( wt4 ( solid 9 wat] 7w s7 - w ,! app>5t loss ( weight ( ! solid is equal to ! sum ( its weight 9 air plus ! weight ( ! s9k] 9 wat]1 less ! comb9$ weight ( bo? 9 wat]4 7d7 ,! ,d5sity ( a ,liquid by a ,hydromet]4--,"o may also easily f9d ! d5sity ( any liquid by ,ar*im$es' ,pr9ciple4 ,if "o takes ! rod describ$ 9 ,art4 #df1 & places x 9 wat]1 ! numb] ( cubic c5timet]s ( wat] x displaces indicates its weight 9 grams4 ,on plac+ ! rod 9 ano!r liquid 9 :i* x floats1 x w ( c\rse displace its own weight & ! height to :i* ! liquid rises on ! scale gives ! volume4 ,by divid+ ! weight ( ! rod z %[n by its position 9 wat] by ! volume ( ! liquid displac$ we obta9 ! d5sity ( ! liquid4 ,comm]cial hydromet]s = te/+ ! d5sity ( milk1 alcohol & o!r liquids are made ( glass ( ! =m %[n 9 ,fig4 #bh4 ,! long n>r[ /em p]mits small diff]5ces 9 volume to be notic$1 h5ce !y are m accurate ?an ! rod describ$ 9 ! prec$+ p>agraph4 ,= conv5i5ce ?is rod conta9s a pap] scale1 s t :5 ! height ( ! liquid on ! /em is not$1 ! d5sity is read at once4 ,illu/ration3 ,,fig4 #bh4--;,a hydromet] us$ to f9d ! d5sity ( a liquid4 ,d5sity ( ,liquids by ,loss ( ,weight4 ,weigh a piece ( glass 9 air 7,wa71 9 wat] 7,ww71 & 9 ! liquid to be te/$ 7,wl74 ,!n 7,wa - ,ww7gives ! weight ( ! wat] displac$4 ,& 7,wa - ,wl7 gives ! weight ( ! liquid displac$4 ,h5ce1 7,wa - ,wl7_/7,wa - ,ww7 equals ! specific gravity ( ! liquid4 ,important ,topics #a4 ,def9itions ( d5sity & specific gravity4 #b4 ,me?ods ( f9d+ d5sity3 7a7 regul> solids2 7b7 irregul> solids2 7c7 solids light] ?an wat]2 7d7 liquids by hydromet]2 7e7 liquids by loss ( weight4 ,ex]cises ,note4--,consid] t #a cu4 ft4 ( wat] weighs #fb4d lbs4 ,consid] t #a ccm4 ( wat] weighs #a g4 #a4 ,:at is meant by ! /atem5t t a block ( wood has a specific gravity ( #j4f8 #b4 ,consid]+ t ! d5sity ( ! human body is ! same z t ( wat]1 :at is ! volume ( a #abe-lb4 boy8 ,( a #bej-lb4 man8 ,( a #fb4d-lb4 boy8 ,:at is ! volume ( y\r body8 #c4 ,h[ is ! weight ( l>ge %ips f\nd8 ,give an example4 #d4 ,m5tion ?ree cases :]e det]m9ations ( d5sity are important4 #e4 ,a body weighs #dj g4 9 air1 #ae g4 9 wat]1 #e g4 9 an acid4 ,f9d 7a7 ! d5sity ( ! body2 7b7 its volume2 7c7 d5sity ( ! acid4 #f4 ,if ! specific gravity ( a horse is #a1 :at is ! volume ( a horse weigh+ #ejj kg48 ,( "o weigh+ #abdh lbs48 #g4 ,a weight$ wood5 box s9ks to a dep? ( #bj cm4 9 wat] & #bd cm4 9 alcohol1 & to a dep? ( #ah cm4 9 br9e4 ,:at is ! d5sity ( ! alcohol & ( ! br9e8 #h4 ,a glass /opp] weighs 9 ! air #be g41 9 wat] #ae g41 9 oil #ah g4 ,f9d ! d5sity & volume ( ! /opp]4 ,f9d ! d5sity ( ! oil4 #i4 ,:at w\ld a cubic foot ( wood weigh if ! specific gravity 7 #j4e48 #aj4 ,! specific gravity ( alum9um is #b4g4 ,f9d ! weight ( a cubic foot ( x4 #aa4 ,a block ( wood weighs #dj g4 ,a piece ( lead appe>s to weigh #gj g4 9 wat]4 ,bo? toge!r appe> to weigh #fj g4 9 wat]4 ,f9d ! d5sity ( ! wood4 #ab4 ,a /one weighs #cj g4 9 air1 #bb g4 9 wat]1 & #bj g4 9 salt wat]4 ,f9d ! d5sity ( ! salt wat]4 #ac4 ,w iron s9k 9 m]cury8 ,:y8 #ad4 ,a subm>9e boat weigh+ #bjj tons mu/ h :at volume 9 ord] to float8 #ae4 ,f9d ! weight ( #b cu4 ft4 ( copp] f its d5sity4 #af4 ,:at is ! weight 9 wat] ( a mass ^: specific gravity is #c4c & ^: weight is #ej kg48 #ag4 ,a block ( granite weighs #afef lbs42 its volume is #aj cu4 ft41 :at is its d5sity8 #ah4 ,if ! specific gravity ( h>d coal is #a4ge h[ w\ld y det]m9e h[ _m tons ( coal a b9 w\ld hold8 #ai4 ,a holl[ copp] ball weighs #b kg4 ,:at mu/ be its volume to enable x to j float 9 wat]8 #bj4 ,a mass hav+ a volume ( #ajj ccm4 & a specific gravity ( #b4fg is fa/5$ to #bjj ccm4 ( wood1 specific gravity #j4ee4 ,:at w ! comb9ation weigh 9 wat]8 #ba4 ,a block weigh+ #d oz4 9 air is ti$ to a s9k] :i* appe>s to weigh #ad oz4 9 wat]4 ,bo? toge!r appe> to weigh #f oz4 9 wat]4 ,:at is ! specific gravity ( ! block8 ,,*apt] ,,iv ,,me*anics ,,( ,,gases 7#a7 ,,weight ,,& ,,pressure ,,( ,,! ,,air #ea4 ,weight ( ,air4--,x is said t savages are unaw>e ( ! pres5ce ( air4 ,!y feel ! w9d & he> & see x mov+ ! leaves & bran*es ( ! trees1 b ( air itself !y h little conception4 ,to ord9>y obs]v]s1 x seems to h no weight1 & to (f] little resi/ance to bodies pass+ ?r\gh x4 ,t x has weight may be readily %[n z foll[s3 7,see ,fig4 #bi47 ,if a holl[ metal sph]e1 or a glass flask1 provid$ ) tube & /opcock1 be weigh$ :5 ! /opcock is op51 & !n aft] ! air has be5 exhau/$ f x by an air pump1 a def9ite loss ( weight is noticeable4 ,illu/ration3 ,,fig4 #bi4--,pro( t air has weight4 ,if ! volume ( ! sph]e is kn[n & x is well exhau/$ ( air1 a fair approximation ( ! weight ( air may be obta9$4 ,"u /&>d conditions1 :i* means at ! freez+ temp]ature & a b>ometric pressure ( #gf cm41 a lit] ( air weighs #a4bic g4 :ile #ab cu4 ft4 ( air weigh approximately #a lb4 #eb4 ,pressure ( ,air4--,s9ce air has weight x may be suppos$ to ex]t pressure l a liquid4 ,t x does s may be %[n 9 a v>iety ( ways4 ,if a plung] fitt+ tightly 9 a glass cyl9d] be drawn upw>d1 :ile ! l[] end ( ! tube is "u wat]1 ! wat] w rise 9 ! tube 7,fig4 #cj74 ,! common explanation ( ?is is t ! wat] rises because ( suction4 ,! philosoph]s ( ! anci5t ,greeks expla9$ x by say+ t nature abhors a vacuum1 & !re=e ! wat] rises4 ,nei!r explanation is correct4 ,x 0 f\nd 9 #afdj t wat] w\ld n rise 9 a pump m ?an #cb ft4 despite ! fact t a vacuum 0 ma9ta9$ above ! wat]4 ,galileo 0 appli$ to = an explanation4 ,he said1 evid5tly nature's horror ( a vacuum does n ext5d above #cb ft4 ,galileo began te/s ^u ! p[] ( a vacuum b dy+ left 8 pupil ,torricelli to cont9ue ! exp]im5t4 ,torricelli reason$ t if wat] w\ld rise #cb ft41 !n m]cury1 :i* is #ac4f times z d5se z wat]1 w\ld rise ab\t #a_/ac z mu*4 ,to te/ ?is1 he p]=m$ ! foll[+ fam\s exp]im5t4 ,illu/ration3 ,,fig4 #cj4--;,air pressure =ces ! liquid up ! tube4 #ec4 ,torricelli's ,exp]im5t 7#afdc74--,take a glass tube ab\t #c ft4 long1 seal$ at "o end1 & fill x ) m]cury4 ,close ! end ) ! f+] & inv]t1 plac+ ! end clos$ by ! f+] "u m]cury 9 a di% 7,fig4 #ca74 ,remove ! f+] & ! m]cury s9ks until ! top ( ! m]cury is ab\t #cj 94 above ! level ( ! m]cury 9 ! di%4 ,torricelli conclud$ t ! rise ( liquids 9 exhau/$ tubes is due to ! pressure ( ! atmosph]e act+ on ! surface ( ! m]cury 9 ! di%4 ,to te/ ?is1 place ! tube ) its m]cury ^u ! plate ( an air pump & place a tubulat$ bell j> ov] ! app>atus s t ! tube projects ?r\gh a tightly fitt+ /opp]4 7,see ,fig4 #cb47 ,if ! air pressure is ! cause ( ! rise ( m]cury 9 ! tube1 on remov+ ! air f ! bell j> ! m]cury %\ld fall 9 ! tube4 ,?is is se5 to happ5 z soon z ! pump is />t$4 ,x is difficult to remove all ! air f ! receiv] s ! m]cury r>ely falls to ! same level 9 ! tube z 9 ! di%4 ,a small tube conta9+ m]cury is (t5 atta*$ to air pumps to indicate ! degree ( exhau/ion4 ,su* tubes are call$ manomet]s4 ,illu/ration3 ,,fig4 #ca4--,torricelli's exp]im5t4 ,illu/ration3 ,,fig4 #cb4--,! m]cury drops z ! air is remov$4 #ed4 ,! ,am\nt ( ,atmosph]ic ,pressure4--,torricelli's exp]im5t enables u to compute readily ! pressure ( ! atmosph]e1 s9ce x is ! atmosph]ic pressure t balances ! column ( m]cury 9 ! tube4 ,by ,pascal's ,law1 ! pressure ( ! atmosph]e on ! surface ( ! m]cury 9 ! di% is transmitt$ z an exactly equal pressure on ! m]cury column 9 ! tube at ! same level z ! m]cury outside4 ,?is pressure1 due to ! air1 mu/ balance ! weight ( ! column ( m]cury 9 ! tube4 ,x !re=e equals ! weight ( ! column ( m]cury ( unit cross-section4 ,! av]age height ( ! column ( m]cury at sea-level is #gf cm4 ,s9ce ! weight ( #a cc4 ( m]cury is #ac4f grams1 ! pressure inside ! tube at ! level ( ! surface ( ! m]cury 9 ! di% is equal to #a #gf #ac4f or #ajcc4f g4 p] squ>e c5timet]4 ,!re=e ! atmosph]ic pressure on ! surface ( ! m]cury 9 ! di% is #ajcc4f g4 p] squ>e c5timet]1 approximately #a kg4 p] squ>e c5timet] or #ae lbs4 p] squ>e in*4 #ee4 ,pascal's ,exp]im5t4--,pascal te/$ 9 ano!r way ! action ( atmosph]ic pressure ^u ! column ( m]cury by reque/+ 8 bro!r-9-law1 ,p]ri]1 :o liv$ ne> a m\nta91 to try ! exp]im5t on its top4 ,p]ri] f\nd t on asc5d+ #ajjj met]s ! m]cury fell #h cm4 9 ! tube4 ,travel]s1 surveyors1 & aviators frequ5tly det]m9e ! altitude above sea-level by read+ ! b>omet]1 an asc5t ( #aa met]s giv+ a fall ( ab\t #a mm4 9 ! m]cury column1 or #j4a 94 = e #ij ft4 ( asc5t4 ,illu/ration3 ,,fig4 #cc4--;,a /&>d b>omet]4 #ef4 ,! ,b>omet]4--,! mod]n b>omet] 7,fig4 #cc71 consi/s ( a ,torricellian tube prop]ly m\nt$4 ,read+ a b>omet] consi/s 9 accurately read+ ! height ( ! m]cury column4 ,?is height v>ies f #ge to #gf4e cm4 or #bi to #cj 94 9 localities n f> f ! sea-level4 ,! atmosph]ic pressure v>ies because ( di/urbances 9 ! atmosph]e4 ,x is f\nd t ^! di/urbances ( ! atmosph]e pass across ! c\ntry f we/ to ea/ 9 a some:at regul> mann]1 h5ce a s]ies ( read+s ( ! b>omet] may give reliable in=mation ( ! movem5t ( ^! di/urbances & s assi/ 9 =eca/+ ! wea!r4 ,! wea!r ,bureau has obs]vations tak5 at ! same mom5t at v>i\s /ations ov] ! c\ntry4 ,^! obs]vations =m ! basis = ! daily =eca/ ( ! wea!r4 ,illu/ration3 ,,fig4 #cd4--;,an an]oid b>omet] ,ano!r =m ( b>omet] 9 common use is ! ,an]oid ,b>omet] 7,fig4 #cd74 ,its ess5tial p>ts are a cyl9drical air-tight box ) an ela/ic corrugat$ cov]4 ,inside ! box is a p>tial vacuum4 ,?is makes ! cov] v s5sitive to slight *anges ( pressure4 ,! motion ( ! top ( ! box is convey$ by a s]ies ( lev]s to an indicat+ h& :i* moves ov] a dial4 ,?is b>omet] c be made s s5sitive z to indicate ! *ange ( air pressure f a table top to ! floor4 ,x is mu* us$ by travel]s1 explor]s1 survey+ p>ties & aviators1 s9ce ! m]curial b>omet] is inconv5i5t to c>ry4 ,important ,topics #a4 ,weight & ,pressure ( air 9 ,engli% & metric units4 ,h[ %[n4 ,evid5ces4 #b4 ,"w ( ,galileo1 ,torricelli1 & ,p]ri]4 #c4 ,b>omet]3 con/ruction1 action1 m]curial1 an]oid4 ,illu/ration3 ,,fig4 #ce4--;,air pressure keeps ! wat] ,9 ! tumbl]4 ,illu/ration3 ,,fig4 #cf4--;,cross-section ( a mod]n dr9k+ f\nta94 ,ex]cises #a4 ,d y ?9k ,ar*im$es' ,pr9ciple applies to ! air8 ,does ,pascal's ,law8 ,:y8 #b4 ,f9d ! d[nw>d pressure ( ! m]cury 9 a b>omet] tube if ! cross-section is #a sq4 cm4 & ! height #ge cm4 at ! level ( ! m]cury surface 9 contact ) ! air4 7,! d5sity ( m]cury is #ac4f grams p] cc47 #c4 ,:at is ! weight ( ! air 9 a room if x is #aj #h #d met]s8 #d4 ,:at weight ( air is 9 a room #aj #ae #aj ft48 #e4 ,:5 smoke rises 9 a /raight l9e f *imneys1 is x an indication ( a high or l[ b>ometric pressure8 ,:y8 #f4 ,:y does a tumbl] fill$ ) wat] & inv]t$ 9 a di% ) its rim "u wat] rema9 full8 #g4 ,if ! b>omet] tube is incl9$ ! m]cury rema9s at ! same horizontal level4 ,h[ c ?is be expla9$8 #h4 ,:5 ! m]curial b>omet] /&s at #gf cm41 h[ high w\ld a wat] b>omet] /&8 ,expla94 #i4 ,expla9 :y x is possible = "o to suck soda wat] ?r\gh a tube8 #aj4 ,fill a tumbl] ) wat]4 ,place a %eet ( pap] ov] ! top & inv]t4 ,! pap] cl+s to ! tumbl] & prev5ts ! wat] f escap+4 ,expla94 7,see ,fig4 #ce47 #aa4 ,:y mu/ a k]os5e oil c h two op5+s 9 ord] to all[ ! oil to fl[ freely8 #ab4 ,expla9 ! action ( ! mod]n dr9k+ f\nta9 7,fig4 #cf74 7#b7 ,,compressibility ,,& ,,expansibility ,,( ,,! ,,air #eg4 ,effect ( ,pressure on ,liquids & ,gases4--,bo? classes ( fluids1 liquids & gases1 h _m *>act]i/ics 9 common4 ,bo? are compos$ ( molecules t move freely2 h5ce bo? fl[4 ,at any po9t )9 a fluid ! pressure is ! same 9 all directions4 ,ar*im$es' ,pr9ciple applies1 !re=e1 to bo? liquids & gases4 ,we n[ come to an important diff]5ce betwe5 liquids & gases4 ,liquids are practically incompressible4 ,s mu* s1 t if wat] is subject$ to a pressure ( #cjjj kg4 p] sq4 cm41 its volume is r$uc$ only ab\t "o-t5?4 ,gases %[ a v diff]5t behavior f liquids on be+ subject$ to pressure4 ,!y may readily be compress$ to a small fraction ( _! volume z is notic$ on inflat+ a pneumatic tire4 ,a gas has also ! ability to spr+ back to a l>g] volume z soon z ! pressure is releas$1 z :5 a cork is driv5 f a pop gun4 ,n only is compress$ air able to exp&1 b air "u ord9>y conditions w exp& if x is releas$ 9 a space :]e ! pressure is less4 ,holl[ bodies1 animals & plants1 are n cru%$ by atmosph]ic pressure1 because ! air & gases conta9$ )9 ex]t z mu* =ce outw>d z ! air ex]ts inw>d4 #eh4 ,boyle's ,law4--,! relation betwe5 ! volume & pressure ( a gas 0 fir/ inve/igat$ by ,rob]t ,boyle 9 ! sev5te5? c5tury4 ,! exp]im5t by :i* he fir/ discov]$ ! law or ! relation betwe5 ! volume & ! pressure ( a gas is briefly describ$ z foll[s3 ,illu/ration3 ,,fig4 #cg a4 ,,fig4 #cg b4 ,,figs4 #cg a ,,& #cg b4--,boyle's law app>atus4 ,a glass tube is b5t 9 ! =m ( ! capital lett] ,j1 ! %ort arm be+ clos$4 ,a little m]cury is p\r$ 9 to cov] ! b5d4 7,see ,fig4 #cg a47 ,s9ce ! m]cury is at ! same level 9 bo? arms1 ! pressure 9 7,a7 is ! same z 9 7,b74 ,m]cury is n[ p\r$ into 7,a7 until x /&s 9 ! long tube at a height above t 9 7,b7 :i* is equal to ! height ( ! m]cury column ( ! b>omet]4 7,see ,fig4 #cg b47 ,! air 9 7,,bc7 is n[ "u a pressure ( two atmosph]es 7"o atmosph]e is due to ! m]cury column74 ,on measurem5t ! air 9 7,,bc7 w be f\nd to h j "o-half ( its orig9al volume4 ,?us d\bl+ ! pressure to :i* a gas is subject$ r$uces its volume to "o-half4 ,tripl+ ! pressure1 r$uces ! volume to "o-?ird & s on4 ,c>eful exp]im5ts reveal ! foll[+ law3 ,! volume ( a giv5 mass ( gas at con/ant temp]ature is inv]sely proportional to ! pressure to :i* x is subject$4 ,?is law is (t5 express$ ma!matically4 ,p_/,p ,v_/,v1 or ,,pv ,p,v4 ,s9ce d\bl+ ! pressure r$uces ! volume "o-half1 x d\bles ! d5sity4 ,tripl+ ! pressure triples ! d5sity4 ,we !re=e h ,p_/,p ,d_/,d or ! d5sity ( a gas directly proportional to its pressure4 ,illu/ration3 ,,fig4 #ch4--;,height & d5sity ( ! air4 #ei4 ,height ( ! ,atmosph]e4--,f its prop]ties ( compression & expansion1 ! air v>ies 9 d5sity & pressure z "o asc5ds 9 x4 ,at a height ( #c miles ! pressure is r$uc$ to ab\t "o-half4 ,?is is an indication t "o-half ( ! air is bel[ ?is level4 ,ballooni/s h gone to a height ( #g miles1 ,glas] & ,coxwell 9 ,engl& 9 #ahfb & ,b]son 9 ,france 9 #aija4 ,! atmosph]e has be5 explor$ to a height ( #cj1ejj met]s 7#ah4ie miles7 by s5d+ up self-regi/]+ b>omet]s 9 small balloons :i* bur/ at great altitudes4 ,a p>a*ute protects ! in/rum5ts f breakage f too rapid fall4 ,?is height ( #cj1ejj met]s 0 rea*$ by a balloon s5t up by ,william ,r4 ,blair1 at ,huron1 ,s\? ,dakota1 ,septemb] #a1 #aiaj4 ,at a height ( #ce miles1 ! d5sity is e/imat$ at #a_/cj1jjj ( its value at sea-level4 7,see ,fig4 #ch47 ,x is believ$ t "s r>efi$ air exi/s = a consid]able di/ance above ?is po9t1 "s e/imates plac+ ! ext5t at #ajj miles1 & o!rs f #bjj to #ejj miles4 ,evid5ces ( "s air at su* heights are %[n by3 7a7 ! height at :i* meteors fir/ appe>1 7b7 ! height ( ! ,aurora ,borealis1 & 7c71 ! di/ance t ! sun is bel[ ! horizon :5 ! la/ traces ( color disappe> f ! sky 9 ! ev5+4 ,al?\gh ! exact limits ( ! atmosph]e are unkn[n1 ! weight ( a column ( air #a sq4 cm4 9 cross-section1 & ext5d+ upw>d z high z ! atmosph]e1 may be accurately comput$4 ,= ?is column ( air exactly balances ! column ( m]cury 9 ! tube ( ! b>omet]4 ,bel[ sea-level1 ! air increases rapidly 9 d5sity & x is e/imat$ t at a dep? ( #ce miles1 ! d5sity ( ! air w\ld be a ?\s& times t at ! e>?'s surface1 or m ?an t ( wat]4 ,important ,topics #a4 ,evid5ce ( compressibility ( gases & incompressibility ( liquids4 #b4 ,boyle's ,law4 ,pro(1 applications4 #c4 ,ext5t ( ! atmosph]e--?ree evid5ces4 ,ex]cises #a4 ,m5tion ?ree illu/rations ( ! compressibility & expansibility ( air t y "k f y\r own exp]i5ce4 #b4 ,increas+ ! pressure increases ! am\nt ( a gas t w be absorb$ by a liquid8 ,expla9 ?is4 ,h y ev] obs]v$ ?is fact8 ,:]e8 #c4 ,if a toy balloon conta9+ #bjjj ccm4 ( gas at ! e>?'s surface :]e ! b>omet] read+ is #gf cm41 rises to an elevation :]e ! b>omet] reads #ed cm41 ! balloon w t5d to exp& to :at volume8 ,expla94 ,w x atta9 ?is volume8 #d4 ,if a gas is compress$1 x *anges 9 temp]ature4 ,h[ d y expla9 ?is8 #e4 ,:at *ange 9 temp]ature w occur :5 compress$ air is all[$ to exp&8 ,expla94 #f4 ,air bl[+ up a m\nta9 side has its pressure less5$ z x approa*es ! top4 ,h[ w ?is affect ! temp]ature8 ,:y8 ,:at may result f ?is *ange 9 temp]ature8 ,expla94 #g4 ,to :at pressure mu/ #ejj ccm4 ( air be subject$ to compress x to #cjj ccm4 ! b>omet] read+ at fir/ be+ #ge cm4 ,expla94 ,illu/ration3 ,,fig4 #ci4--,! air pump4 7#c7 ,,pneumatic ,,appliances #fj4 ,! ,air ,pump4--,! air pump is us$ to remove air or o!r gases f a clos$ vessel4 ,x 0 inv5t$ ab\t #afej by ,otto ,von ,gu]icke1 burgoma/] ( ,magdeburg1 ,g]many4 ,"o =m ( air pump is %[n 9 ,fig4 #ci4 ,c is a cyl9d] )9 :i* slides a tightly fitt+ pi/on4 ,r is ! vessel f :i* ! air is to be exhau/$4 r & u are valves op5+ upw>d4 ,! action ( ! pump is z foll[s3 ,on pu%+ ! pi/on d[n1 ! air 9 ,c is compress$4 ,?is op5s valve r all[+ ! conf9$ air to escape above ! pi/on4 ,! pi/on is !n rais$ mak+ ! space 9 ,c a p>tial vacuum4 ,! pressure 9 ,r n[ be+ great] ?an 9 ,c1 u is pu%$ up & ! air f ,r ru%es into ,c1 until ! pressure is equaliz$4 ,on pu%+ d[n ! pi/on aga91 valve u closes & ! process is repeat$ until ! pressure 9 ,r is no long] able to raise ! valve u4 ,"s air pumps are s con/ruct$ t ! valves are op5$ & clos$ automatically by ! movem5t ( ! pi/on4 ,) ^! pumps a high] degree ( r>efaction c be obta9$4 ,air is (t5 p>tially exhau/$ f receiv]s or vessels by ! use ( a filt] pump or aspirator4 ,a /ream ( wat] fl[+ ?r\gh a con/riction causes a r$uc$ pressure1 draws 9 air & c>ries x away1 & ?us produces a p>tial vacuum4 ,see ,fig4 #dj = a section ( ! device4 ,illu/ration3 ,,fig4 #dj4--;,an aspirator4 #fa4 ,! ,cond5s+ ,pump4--,?is is l ! exhau/ pump except t its valves are rev]s$4 ,x is us$ 9 compress+ illum9at+ gases into cyl9d]s = use 9 light+ vehicles1 /]eopticons1 ,p9ts* lights1 gas light buoys1 etc41 & also = compress+ air to op]ate air brakes1 pneumatic hamm]s & drills1 & = o!r uses4 ,! common cond5s+ pump is ! k9d us$ = inflat+ tires4 7,see ,fig4 #da47 ,9 ?is1 a loosely fitt+ metal pi/on is atta*$ to a disc ( lea!r some:at l>g] ?an ! cyl9d]4 ,?is device is call$ a cup valve4 ,on rais+ ! pi/on1 air ru%es 9 f ! top pa/ ! valve1 b on pu%+ ! pi/on d[n1 ! valve is press$ tightly aga9/ ! sides ( ! cyl9d] & prev5ts ! escape ( any air4 ,! compress$ air pu%es op5 a valve on ! tire & ent]s x4 ,?is valve closes z soon z ! pressure is less5$ f outside4 ,x is well to notice 9 all ( ^! pumps t two valves are us$4 ,"o holds ! air already secur$ :ile ! o!r op5s = a new supply4 ,bo? valves are nev] op5 at ! same "t4 ,illu/ration3 ,,fig4 #da4--;,cond5s+ pump us$ 9 inflat+ tires4 #fb4 ,wat] ,pumps4--,! ,common ,lift ,pump4 ,?is1 ! simple/ pump = rais+ wat]1 consi/s ( a cyl9d] ,c 7,fig4 #db7 connect$ by a pipe ,r to a supply ( wat] z a ci/]n or well4 ,a valve op5+ upw>d is plac$ at ! bottom ( ! cyl9d] ov] ! entrance to ! pipe4 ,9 ! cyl9d] is a tightly fitt+ pi/on connect$ by a rod to a lev] = ease 9 action4 ,! pi/on conta9s a valve op5+ upw>d4 ,9 op]at+ ?is pump wat] is usually fir/ p\r$ into ! cyl9d] to prime x4 ,?is helps to close ! valves & prev5ts air leak+ pa/ !m4 ,:5 ! pi/on is l[]$ ! l[] valve closes1 ! air 9 ! cyl9d] be+ compress$ pu%es ! upp] valve op5 & passes above ! pi/on4 ,on rais+ ! pi/on ! upp] valve closes4 ,?is =ms a p>tial vacuum 9 ! cyl9d]4 ,! air press+ on ! surface ( ! wat] bel[ =ces ! wat] & air t may be 9 ! tube upw>d ?r\gh ! l[] valve to fill ?is p>tial vacuum4 ,:5 ! cyl9d] becomes fill$ ) wat]1 ?is is lift$ out on ! up-/roke1 :5ce its "n1 lift pump4 ,s9ce ! atmosph]ic pressure at sea-level c only support a column ( wat] ab\t #cd ft4 high1 ! l[] valve mu/ be )9 ?is di/ance ( ! wat] surface4 ,9 actual practice ! limit is ab\t #bg ft4 ,9 deep] wells1 ! cyl9d] & valves are plac$ s t !y are )9 #be or #bg ft4 ( ! surface ( ! wat] 9 ! well1 a long pi/on rod rea*+ above ! surface ( ! gr\nd & connect$ to a pump h&le op]ates ! pi/on4 ,a dis*>ge pipe ext5ds f ! cyl9d] to ! surface ( ! gr\nd above4 ,illu/ration3 ,,fig4 #db4--,! common lift pump4 ,illu/ration3 ,,fig4 #dc4--;,a =ce pump ) an air *amb] 7,a74 #fc4 ,! ,=ce ,pump4--,! =ce pump is us$ to deliv] wat] "u pressure ei!r = spray+ or to an elevat$ res]voir4 ,! pi/on is solid1 ! second valve be+ plac$ at ! entrance ( ! dis*>ge pipe4 7,see ,fig4 #dc47 ,! action is ! same z t ( ! lift pump1 ) ?is exception2 ! pi/on 9 its d[n /roke =ces ! wat] out ?r\gh ! dis*>ge pipe1 ! velocity dep5d+ ^u ! pressure ex]t$4 ,a =ce pump is usually provid$ ) an air *amb] :i* is connect$ ) ! dis*>ge pipe4 ,on ! d[n /roke ( ! pi/on1 wat] is =c$ into ! air *amb]4 ,?is compresses ! air x conta9s4 ,! compress$ air reacts & ex]ts pressure on ! wat] =c+ x out 9 a /eady /ream4 ,=ce pumps are us$ 9 deep wells1 be+ plac$ at ! bottom4 ,! pumps us$ 9 city wat] works1 fire eng9es1 & all /eam pumps1 are =ce pumps4 7,see ,fig4 #dd47 ,illu/ration3 ,,fig4 #dd4--;,a /eam pump us$ on a fire eng9e4 #fd4 ,! ,siphon4--,! siphon is a tube us$ to convey a liquid f "o level ov] an elevation to a l[] level by atmosph]ic pressure4 ,x is us$ to remove liquids f tanks or vessels t h no op5+ at ! bottom4 ,! siphon _c be completely und]/ood until "o has ma/]$ ! laws ( ! fl[ ( liquids4 ,! foll[+ is (f]$ z an incomplete explanation ( its behavior4 ,consid] ! siphon to be full ( wat] & clos$ at d 7,fig4 #de74 ,atmosph]ic pressure on a w hold ! siphon full if ab does n exce$ #cd feet4 ,if d is op5$ ! wat] falls out ) a spe$ equal to t acquir$ 9 fall+ f ! level ( a to t ( d4 ,?is spe$ is acquir$ by all ! wat] 9 ! siphon & results 9 a drop 9 pressure ?r\gh\t x4 ,! pressure at a inside ! siphon becomes less ?an ! pressure at ! same level outside z soon z ! wat] />ts fl[+4 ,! wat] 9 ! vessel !n fl[s into ! siphon & out at d4 ,?is fl[ cont9ues z long z !re is a fall f ! free surface ( ! wat] 9 ! vessel to ! outlet at d4 ,illu/ration3 ,,fig4 #de4--;,cross-section ( a siphon4 ,illu/ration3 ,,fig4 #df4--,! ,c>tesian div]4 #fe4 ,! ,c>tesian ,div]4--,?is is a device :i* illu/rates at ! same "t transmission ( pressure by liquids1 ,ar*im$es' pr9ciple1 & compressibility ( gases4 ,x 0 inv5t$ by ,des ,c>tes 7#aeif-afej74 ,z ord9>ily made1 x is a holl[ glass image ) a small op5+ 9 ! foot4 ,x conta9s air & wat] 9 su* am\nts t ! av]age d5sity ( image & cont5ts is slightly less ?an t ( wat]4 ,x is plac$ 9 a tall glass j> fill$ ) wat] & cov]$ ) tightly /ret*$ rubb] tissue4 7,see ,fig4 #df47 ,by press+ on ! rubb] cov] ! div] may be made to s9k1 s9ce ! air & wat] transmit ! pressure on ! cov] :i* compresses ! air inside ! figure admitt+ "s wat] to x1 ?us mak+ ! div] m d5se ?an wat]4 ,by v>y+ ! pressure x c be made to s9k1 rise1 or rema9 /ation>y at w4,d ,a small vial c be us$ in/ead ( ! image4 ,d ,! position ( a subm>9e 9 or "u wat] is controll$ 9 a simil> mann]4 #ff4 ,hydraulic ,ram4--,! hydraulic ram 7see ,fig4 #dg7 is an automatic device t is mu* us$ = rais+ wat] f spr+s to h\ses locat$ on high] gr\nd4 ,wat] fl[s ?r\gh ! pipe ,a ?r\gh ! op5+ at ,b4 ,! pressure closes ! valve at ,b4 ,! increas$ pressure 9 ! pipe due to ! clos+ ( ,b op5s ! valve ,c & "s ( ! wat] fl[s into ! air *amb] ,d4 ,?is r$uces ! pressure aga9/ ! valve ,b s t x drops & all[s a little wat] to escape4 ,j z ?is happ5s1 valve ,c closes4 ,! pressure 9 ! pipe !n closes ,b & =ces wat] pa/ ,c4 ,?is action be+ cont9ually repeat$1 ! air 9 ,d becomes s compress$ t x has ela/ic =ce en\gh to raise ! wat] 9 a /eady /ream to a height ( _m feet4 ,illu/ration3 ,,fig4 #dg4--;,cross-section ( a hydraulic ram4 #fg4 ,! ,balloon4--,s9ce air is a fluid1 ,ar*im$es' pr9ciple applies to x z well z to liquids4 ,!re=e any object 9 ! air is lift$ up by a =ce equal to ! weight ( ! air x displaces4 ,! object w rise1 if x weighs less ?an ?is displac$ air & w cont9ue to rise until bo? weights are equal4 ,! ,balloon 7,fig4 #dh7 rises because x weighs less ?an ! air x displaces1 & !re=e x is pu%$ up by ! heavi] air1 ! lift+ p[] be+ ! diff]5ce betwe5 its weight & t ( ! air displac$4 ,! neck at ! bottom is left op5 to all[ = expansion ( ! gas4 ,:5 ! a]onaut wi%es to desc5d1 he op5s a valve at ! top all[+ "s ( ! gas to escape4 ,illu/ration3 ,,fig4 #dh4--,w9n] ( int]national *ampion%ip race1 ,p>is1 #aiac4 ,hydrog5 is ! lighte/ gas1 weigh+ #j4ji kg4 p] cubic met]1 & s gives ! greate/ lift+ p[]1 b z x is exp5sive to make1 coal gas1 d5sity #j4ge kg4 p] cubic met]1 is ord9>ily employ$4 ,helium has rec5tly be5 us$ to fill milit>y balloons because x _c be set on fire4 ,! ,p>a*ute 7,fig4 #di7 is an umbrella-%ap$ device = use 9 desc5d+ f a balloon4 ,aft] fall+ a few seconds x op5s1 ! l>ge surface expos$ to ! air caus+ x to desc5d sl[ly4 ,! hole 9 ! top keeps ! p>a*ute upright by all[+ ! air to escape ?r\gh x1 ?us reliev+ ! pressure4 ,illu/ration3 ,,fig4 #di4--;,a p>a*ute4 ,illu/ration3 ,,fig4 #ej4--;,cross-section ( a ,we/+h\se air brake4 #fh4 ,! ,air ,brake4--,compress$ air is us$ to d "w 9 _m ma*9es1 su* z pneumatic drills1 hamm]s1 & air brakes4 ,! ,we/+h\se air brake 7,fig4 #ej7 uses air at a pressure ( ab\t #gj lbs4 to ! squ>e in*4 ,! ess5tial p>ts z %[n are a res]voir ,r1 ! brake cyl9d] ,c & a triple valve ,v1 plac$ "u ea* c> ) an air pipe ,p1 lead+ to ! eng9e4 ,?is is connect$ to ,r by ! triple valve ,v4 ,:5 ! pressure 9 ,p is r$uc$ by ! eng9e] or by accid5t1 ! triple valve op]ates s z to admit air f ,r into ! cyl9d] ,c pu%+ ! pi/on ,h to ! left4 ,h is connect$ to ! brakes by lev]s :i* press ! brake %oes /rongly aga9/ ! :eels4 ,:5 ! air pressure 9 ,p is re/or$ ! triple valve acts s z to p]mit ! air 9 ,c to escape :ile ,r is fill$ aga9 f ,p4 ,! hiss+ s\nd he>d :5 a tra9 /ops is caus$ by air escap+ f cyl9d] ,c4 ,! spr+ 9 ,c keeps ! brakes f ! :eels except :5 ! air is on4 ,illu/ration3 ,,fig4 #ea4--;,cross-section ( a gas met] %[+ its con/ruction & action4 #fi4 ,! ,gas ,met]4--,! gas met] consi/s ( a box divid$ into two p>ts by a v]tical p>tition 7,fig4 #ea74 ,two bell[s are atta*$ to ?is p>tition1 "o on ea* side4 ,! valves t regulate ! fl[ ( gas to & f ! bell[s & ! *amb]s ,a & ,d are op5$ & clos$ by lev]s connect$ ) ! bell[s4 ,^! lev]s also op]ate ! h&s ^u ! dials4 ,:5 ! inlet to ! bell[s ,b is op5$1 ! outlet ( ,a is also op5$4 ,gas ent]+ ,b op5s ! bell[s & =ces ! gas 9 ,a out into ! h\se-pipe ,e4 ,:5 ,b is full its inlet valve closes & its outlet valve op5s4 ,! inlet ( ,a also op5s & its outlet closes4 ,gas n[ fl[s into ,a1 compress+ ! bell[s & ,b1 & =c+ ! gas f x into ! h\se-pipe4 ,at ea* fill+ ( ! bell[s ,b !re w be displac$ f ,a & =c$ into ! h\se-pipe z mu* gas z ent]s ,b4 ,x is evid5t t at ea* empty+ ( ,b an equal am\nt ( gas ent]s ,a4 ,?us we h ,a & ,b alt]nately fill+ & empty+ z long z ! gas burn] is op54 ,to h a cont9u\s fl[ ( gas 9 ! h\se-pipes two pipes & two *amb]s are necess>y1 "o be+ fill$ :ile ! o!r is be+ empti$4 ,fig4 #eb repres5ts ! dials ^u a gas met] %[+ a read+ ( #ed1fjj cu4 ft4 ,illu/ration3 ,,fig4 #eb4--;,dials ( a gas met]4 #gj4 ,c5trifugal ,pumps4 ,fluids1 su* z wat] & air1 are (t5 put 9 motion by devices call$ c5trifugal pumps 7see ,art4 #gh74 ,^! pumps conta9 a revolv+ "p1 l a :eel )\t a rim1 ^: spokes are replac$ by ?9 blades4 ,?is revolv+ "p resembles ! paddle :eel ( "s /eam boats & is enclos$ 9 a case or cov] hav+ "o op5+ at ! rim & ano!r op5+ on "o side ab\t ! axle4 ,illu/ration3 ,,fig4 #ec4--;,a vacuum sweep]4 7,c\rtesy ( ! ,hoov] ,suction ,sweep] ,co47 ,:5 ! :eel is rapidly revolv$1 ! fluid is driv5 out ) consid]able =ce ?r\gh ! op5+ at ! rim1 :ile a p>tial vacuum is produc$ at ! axle caus+ a rapid fl[ into ! device at ?is po9t4 ,?is is ! pr9ciple ( ! action ( ! vacuum clean]4 ,fig4 #ec is a section ( a vacuum sweep] %[+ ! revolv+ :eel & ! curr5t ( air pass+ into ! :eel at ! l[] side & out ( ! rim ( ! case at ! re>4 ,c5trifugal wat] pumps "w on ! same pr9ciple & furni% a cont9u\s fl[ ( wat]1 (t5 l>ge 9 volume & at consid]able pressure4 ,important ,topics #a4 ,air pump4 #b4 ,cond5s+ pump4 #c4 ,lift & =ce pumps4 #d4 ,siphon4 #e4 ,c>tesian div]4 #f4 ,hydraulic ram4 #g4 ,balloon4 #h4 ,air brake4 #i4 ,gas met]4 #aj4 ,vacuum clean]4 ,ex]cises #a4 ,expla9 :y smoke settles to ! gr\nd be=e /orms4 #b4 ,:y does ! wat] rise 9 ! suction pipe ( a pump8 #c4 ,:y is x easi] to float 9 wat] :5 ! lungs are fill$ ) air ?an :5 !y are n fill$8 #d4 ,:y is x easi] to swim 9 salt wat] ?an 9 fre% wat]8 #e4 ,h[ are subm>9es made to s9k8 to rise to ! surface8 #f4 ,h[ c a fi% rise or s9k 9 wat]8 #g4 ,expla9 :y a life pres]v] made ( cork w enable a p]son to float4 #h4 ,hold ! op5 h& out flat ) ! f+]s toge!r4 ,place und]nea? ! f+]s a piece ( pap]4 ,bl[ betwe5 ! fir/ & second f+]s aga9/ ! pap]4 ,z long z y bl[ h>d ! pap] w n fall b w /ick to ! h&4 ,expla94 #i4 ,:y does press+ ! bulb ( an atomiz] =ce out ! liquid 9 a f9e spray8 #aj4 ,:y is air t conta9s a l>ge am\nt ( wat] vapor light] ?an air t only conta9s a small am\nt8 #aa4 ,h[ are heights above sea-level asc]ta9$ by a b>omet]8 #ab4 ,oil floats on wat] b s9ks 9 alcohol4 ,expla94 #ac4 ,9 a balloon ! l[] end is (t5 op5 to ! air4 ,:y does n ! gas escape & prev5t ! balloon f ris+8 #ad4 ,h[ long w a balloon cont9ue to rise8 #ae4 ,if ! pressure aga9/ ! #h-;94 pi/on ( an air brake is #gj lbs4 p] squ>e in*1 h[ mu* =ce does ! pi/on ex]t8 #af4 ,! capacity ( a balloon is #dj1jjj cu4 ft4 ,! weight ( ! balloon1 c>1 etc41 is #fjj lbs42 specific gravity ( ! gas us$ is #j4df t ( ! air4 ,f9d h[ mu* weight ! balloon c c>ry4 #ag4 ,! s-call$ ,magdeburg hemisph]es 7 inv5t$ by ,otto von ,gu]icke ( ,magdeburg1 ,g]many4 ,:5 ! hemisph]es 7see ,fig4 #ed7 are plac$ 9 contact & ! air exhau/$ x is f\nd v difficult to pull !m ap>t4 ,expla94 #ah4 ,von ,gu]icke's hemisph]es _h an inside diamet] ( #bb 94 ,:at =ce w\ld be requir$ to pull !m ap>t if all ! air 7 exhau/$ f !m8 7,f9d ! atmosph]ic =ce on a circle1 #bb 94 9 diamet]47 #ai4 ,von ,gu]icke made a wat] b>omet] ^: top ext5d$ ?r\gh ! ro( ( 8 h\se4 ,on ! top ( ! wat] 9 ! tube 0 plac$ a wood5 image4 ,9 fair wea!r ! image appe>$ above ! ro(1 b x desc5d$ be=e a /orm4 ,expla94 #bj4 ,! balloon ,goodye> 7,fig4 #dh71 :i* won ! ,int]national *ampion%ip race at ,p>is 9 #aiac1 has a capacity ( #hj1jjj cu4 ft4 ,! gas bag weighs #fec lbs41 ! net #bdj lbs4 & ! basket #ib lbs4 ,h[ l>ge a load c x c>ry :5 fill$ ) hydrog5 specific gravity #j4jfi 7comp>$ ) air74 ,illu/ration3 ,,fig4 #ed4--,magdeburg hemisph]es4 ,review ,outl9e3 ,liquids & ,gases ,liquids3 ,=ce1 pressure1 & d5sity4 ,float+ & imm]s$ bodies4 ,laws3 ,liquid =ce1 ,f ,a4h4d1 ,pascal's1 ,ar*im$es4 ,illu/rations & ,applications3 ,specific gravity1 ,wa_/7,wa - ,ww71 7,wa - ,wl7_/7,wa - ,ww71 ,boyle's1 ,,pv ,p,v ,devices3 ,hydraulic press1 air cu%ion1 b>omet]--m]curial & an]oid4 ,pumps1 lift1 =ce1 vacuum1 compression1 c5trifugal1 balloon1 siphon1 etc4 ,con/ruction & action ( ea*4 ,,*apt] ,v ,,=ce ,,& ,,motion 7#a7 ,,=ce1 ,,h[ ,,measur$ ,,& ,,repres5t$ #ga4 ,=ce4--,we h be5 /udy+ v>i\s =ces1 su* z air pressure1 pressure 9 liquids1 & ! =ce ( ela/icity 9 solids1 & h consid]$ !m simply z pu%es or pulls4 ,a m =mal /udy ( =ces 9 g5]al & ( devices = repres5t+ & measur+ !m w be helpful at ?is po9t ( ! c\rse4 ,a =ce is t :i* t5ds to cause a *ange 9 ! size or %ape ( a body or 9 its /ate ( motion4 ,9 o!r words a =ce is a pu% or a pull4 ,t is1 =ce t5ds to produce di/ortion or *ange ( motion 9 a body4 ,=ce itself is invisible4 ,we measure x by ! effect x produces4 ,=ces are usually associat$ ) ! objects ex]t+ !m4 ,?us we speak ( muscul> =ce1 air pressure1 liquid pressure1 ! =ce ( a spr+1 ! =ce ( ! e>?'s attraction & s on4 ,=ces are classifi$ 9 v>i\s ways4 ,i4 ,) respect to ! duration & /ead9ess ( ! =ce4 7a7 ,con/ant1 z ! e>?'s attraction4 7b7 ,impulsive1 z ! /roke ( a bat on a ball4 7c7 ,v>iable1 z ! =ce ( ! w9d4 ,,ii4 ,) respect to ! direction ( ! =ce4 7a7 ,attractive1 z ! e>?'s attraction4 7b7 ,repulsive1 z air pressure1 liquid pressure1 etc4 #gb4 ,me?ods ( ,measur+ ,=ce4--,s9ce =ces are measur$ by _! effects :i* are ei!r di/ortion or *ange ( motion1 ei!r ( ^! effects may be us$ to measure !m4 ,= example1 ! =ce ex]t$ by a locomotive is sometimes comput$ by ! spe$ x c develop 9 a tra9 ( c>s 9 a giv5 "t1 or ! =ce ( ! bl[ ( a baseball bat is e/imat$ by ! di/ance ! ball goes be=e x /rikes ! gr\nd4 ,! m common me?od ( measur+ =ce1 h[ev]1 is by di/ortion1 t is1 by measur+ ! *ange ( %ape ( a body caus$ by ! =ce4 ,9 do+ ?is1 use is made ( ,hooke's ,law 7,art4 #cb71 9 :i* x is /at$ t )9 ! limits ( p]fect ela/icity1 *anges ( size or %ape are directly proportional to ! =ces employ$4 ,t is1 twice z great a =ce w produce twice z great a *ange ( %ape & s on4 ,illu/ration3 ,,fig4 #ee4--;,a spr+ balance4 ,a common contrivance us+ ?is pr9ciple is ! spr+ balance 7,fig4 #ee71 ) :i* all are famili>1 z ice scales1 meat scales1 po/al scales1 etc4 ,! object :i* *anges %ape 9 ?is device is a coil$ spr+ conta9$ 9 ! case ( ! in/rum5t4 ,! balance is s con/ruct$ t :5 ! spr+ is pull$ out z f> z possible x has n rea*$ its limit ( ela/icity1 s9ce1 if ! spr+ 7 /ret*$ s z to exce$ its ela/ic limit1 ! index w\ld n return to its fir/ position on remov+ ! load4 7,see ,arts4 #cj-cb47 #gc4 ,graphic ,repres5tation ( ,=ces4--,a =ce is said to h ?ree elem5ts4 ,^! are 7a7 its po9t ( application1 7b7 its direction1 & 7c7 its magnitude4 ,= example1 if !re is hung ^u ! hook ( a spr+ balance a weight ( #e lbs41 !n we h3 7a7 its po9t ( application on ! hook ( ! balance1 7b7 its d[nw>d direction & 7c7 its magnitude1 or #e lbs4 ,^! ?ree elem5ts may be repres5t$ by a l9e4 ,?us 9 ,fig4 #ef;a1 a l9e ,,ab is drawn z %[n1 five units long2 ,a repres5ts ! po9t ( application2 ,b1 ! arr[ head1 %[s ! direction2 & ! l5g? ( ! l9e 7five units7 %[s ! magnitude ( ! =ce4 ,?is is call$ a graphic repres5tation s9ce x repres5ts by a l9e ! quantity 9 "q4 ,if ano!r weight ( #e lbs4 7 hung f ! fir/ "o1 ! graphic repres5tation ( bo? =ces w\ld be z 9 ,fig4 #ef;b4 ,"h ! fir/ =ce is repres5t$ by ,,ab z be=e1 ,,bc repres5t+ ! second =ce appli$4 ,! :ole l9e repres5ts ! resultant ( ! two =ces or ! result ( _! comb9ation4 ,if ! two weights 7 hung "o at ea* end ( a %ort /ick ,,ac 7,fig4 #ef;c71 & ! latt] susp5d$ at its c5t] _! comb9$ weight or resultant w\ld ( c\rse be appli$ at ! c5t]4 ,! direction w\ld be ! same z t ( ! two weights4 ,! resultant !re=e is repres5t$ by ,,on4 ,9 ord] to exactly balance ?is resultant ,,on1 a =ce ( equal magnitude b opposite 9 direction mu/ be appli$ at ! po9t ( application ( ,,on1 or ,o4 ,,om !n repres5ts a =ce t w j balance or hold 9 equilibrium ! resultant ( ! two =ces ,,ab & ,,cd4 ,?is l9e ,,om !re=e repres5ts ! equilibrant ( ! weights ,,ab & ,,cd4 ,! resultant ( two =ces at an angle ) ea* o!r is =m$ diff]5tly1 z 9 ,fig4 #eg a4 ,"h two =ces ,,ab & ,,ac act at an angle ) ea* o!r4 ,lay (f at ! designat$ angle ! l9es ,,ab & ,,ac ( su* l5g? z w accurately repres5t ! =ces4 ,lay (f ,,bd equal to ,,ac & ,,cd equal to ,,ab4 ,! figure ,,abcd is !n a p>allelogram4 ,its diagonal ,,ad repres5ts ! resultant ( ! =ces ,,ab & ,,ac act+ at ! angle ,,bac4 ,if ,,bac equals #ij degrees or is a "r angle1 ,,ad may be comput$ ?us3 ,,ab ,,bd ,,ad4 ,:y8 & ,,ad 7l9e,,ab l9e,,bd74 ,illu/ration3 ,,fig4 #ef4--;,graphic repres5tation ( =ces act+ along ! same or p>allel l9es4 ,illu/ration3 ,,fig4 #eg4--;,graphic repres5tation ( two =ces act+ 7a7 at a "r angle1 7b7 at an acute angle4 ,?is me?od ( det]m9+ ! resultant by computation may be us$ :5 ! two =ces are at "r angles4 7,9 any case1 ,,ad may be measur$ us+ ! same scale t is laid (f ^u ,,ab & ,,ac1 z %[n 9 ,fig4 #eg b47 ,! ?ree cases ( comb9+ =ces j giv5 may be classifi$ z foll[s3 ,! fir/ is t ( two =ces act+ along ! same l9e 9 ! same or opposite direction1 z :5 two horses are hit*$ t&em1 or 9 a tug ( w>4 ,! second is t ( two =ces act+ along p>allel l9es1 9 ! same direction1 z :5 two horses are hit*$ side by side or abrea/4 ,! ?ird is t ( two =ces act+ at ! same po9t at an angle4 ,x may be repres5t$ by ! device %[n 9 ,fig4 #eh1 consi/+ ( two spr+ balances susp5d$ f nails at ! top ( ! blackbo>d at ,a & ,b4 ,a cord is atta*$ to bo? hooks & is pass$ ?r\gh a small r+ at ,o f :i* is susp5d$ a kn[n weight1 ,w4 ,l9es are drawn on ! blackbo>d "u ! /ret*$ cords1 f ,o t[>d ,,oa1 ,,ob1 & ,,ow & di/ances measur$ on ea* f ,o to correspond to ! ?ree =ces z read on balance ,a & ,b & ! weight ,w4 ,let a p>allelogram be con/ruct$ on ! l9es measur$ (f on ,,oa & ,,ob4 ,its diagonal drawn f ,o w be f\nd to be v]tical & ( ! same l5g? z ! l9e measur$ on ,,ow4 ,! diagonal is ! resultant ( ! two =ces & ,,ow is ! equilibrant :i* is equal & opposite to ! resultant4 ,illu/ration3 ,,fig4 #eh4--;,exp]im5tal pro( ( p>allelogram ( =ces4 ,aga91 ! fir/ case may be repres5t$ by a boat mov+ up or d[n a /ream2 ! resultant motion be+ ! comb9$ effect ( ! boat's motion & t ( ! /ream4 ,! second1 may be repres5t$ by two horses atta*$ side by side to ! same ev5]4 ,! resultant =ce equals ! sum ( ! two compon5t =ces4 ,! ?ird1 may be repres5t$ by a boat go+ across a /ream1 ! resultant motion be+ repres5t$ by ! diagonal ( ! p>allelogram =m$ by us+ ! l9es t repres5t ! motion ( ! /ream & ( ! boat4 #gd4 ,units = ,measur+ ,=ce4--,=ce is commonly measur$ 9 units ( weight3 9 p\nds1 kilograms1 & grams4 ,= example1 we speak ( #ae lbs4 pressure p] squ>e in* & #ajcc4f g4 pressure p] squ>e c5timet] z repres5t+ ! air pressure4 ,x %\ld be not$ "h t ! words p\nd1 kilogram1 & gram are us$ n only to repres5t weight or =ce b also ! masses ( ! objects consid]$4 ,?us1 "o may speak ( a p\nd-mass mean+ ! am\nt ( mat]ial 9 ! object4 ,x w help to avoid confusion if we res]ve ! simple t]ms gram & p\nd to d5ote exclusively an am\nt ( matt]1 t is1 a mass1 & to use ! full expression gram ( =ce or p\nd ( =ce :5ev] we h 9 m9d ! pull ( ! e>? ^u ^! masses4 ,or1 "o may speak ( a p\nd-weight mean+ ! am\nt ( attraction ex]t$ by ! e>? ^u ! object4 ,! same is true ( gram-mass & gram-weight4 ,! mass ( a body does n *ange :5 ! body is transf]r$ to ano!r place4 ,! weight1 h[ev]1 may v>y1 = on mov+ a body f ! equator t[>d ! poles ( ! e>? ! weight is kn[n to increase4 ,important ,topics #a4 ,def9ition ( =ce4 #b4 ,classification ( =ces4 7a7 ,duration3 con/ant1 impulsive1 v>iable4 7b7 ,direction3 attractive1 repulsive4 #c4 ,me?ods ( measur+ =ce4 7a7 ,by di/ortion4 7b7 ,by *ange ( motion4 #d4 ,graphic repres5tation ( =ces3 compon5t1 resultant1 equilibrant4 #e4 ,?ree cases ( comb9+ =ces4 7#a7 ,two =ces act+ on ! same l9e4 7#b7 ,two =ces act+ 9 p>allel l9es4 7#c7 ,two =ces act+ at ! same po9t at an angle4 #f4 ,units = measur+ =ce1 p\nd1 gram4 ,ex]cises #a4 ,"n five natural =ces4 ,:i* produce a t5sion8 ,:i* a pressure8 #b4 ,h[ mu* c y lift8 ,express 9 p\nds & kilograms4 #c4 ,%[ graphically ! resultant ( two =ces at "r angles1 "o ( #ab lbs41 ! o!r ( #af lbs4 ,:at is ! magnitude ( ?is resultant8 ,!n det]m9e ! answ]1 fir/ by measurem5t & !n by computation4 ,:i* answ] is m accurate8 ,:y8 #d4 ,repres5t by a p>allelogram ! two =ces t support a p]son sitt+ 9 a hammock & draw ! l9e repres5t+ ! resultant4 #e4 ,f9d graphically ! resultant ( ! pull ( two =ces1 "o ( #ejj lbs4 ea/ & "o ( #fjj lbs4 nor?we/4 #f4 ,det]m9e ! equilibrant ( two =ces1 "o ( #hjj lbs4 s\? & "o ( #fjj lbs4 we/4 #g4 ,w\ld ! fact t weight v>ies on go+ f ! equator to ei!r pole be %[n by a spr+ balance or a beam balance8 ,expla94 7#b7 ,,motion4 ,,newton',s ,,laws ,,( ,,motion #ge4 ,motion a ,*ange ( ,position4--,motion is def9$ z a cont9u\s *ange 9 ! position ( a body4 ,! position ( a body is usually describ$ z its di/ance & direction f "s fix$ po9t4 ,?us a man on a boat may be at re/ ) respect to ! boat & mov+ ) respect to ! e>?4 ,or1 if he walks t[>d ! /]n z fa/ z ! boat moves =w>d1 he may keep directly ov] a rock on ! bottom ( ! lake & h5ce n be mov+ ) ref]5ce to ! rock & yet be 9 motion ) respect to ! boat4 ,motion & re/1 !re=e1 are relative t]ms4 ,! e>? itself is 9 motion 9 turn+ on its axis1 9 mov+ along its orbit1 & 9 foll[+ ! sun 9 its motion ?r\gh space4 ,motions are classifi$ 9 sev]al ways3 7,a7 ,,modes ,,( ,,motion #a4 ,translation4--,a body is said to h motion ( translation :5 e l9e 9 x keeps ! same direction4 #b4 ,rotation4--,a body has motion ( rotation :5 x turns ^u a fix$ axis )9 ! body1 z a :eel ^u its axle or ! e>? ^u its axis4 #c4 ,vibration or ,oscillation4--,a body is said to h vibratory or oscillatory motion :5 x returns to ! same po9t at regul> int]vals by rev]sals ( motion along a giv5 pa?1 e4g41 a p5dulum4 7,b7 ,,direction ,,( ,,motion #a4 ,rectil9e>4--,a body has rectil9e> motion :5 its pa? is a /raight l9e4 ,absolute rectil9e> motion does n exi/1 al?\gh ! motion ( a tra9 on a /raight /ret* ( track is ne>ly rectil9e>4 #b4 ,curvil9e>4--,a body has curvil9e> motion :5 its pa? is a curv$ l9e1 e4g41 ! pa? ( a ?r[n ball4 7,c7 ,,uni=mity ,,( ,,motion #a4 ,uni=m4--,a body has uni=m motion :5 its spe$ & direction ( motion d n *ange4 ,uni=m motion = ext5d$ p]iods is r>ely obs]v$4 ,a tra9 may cov]1 on an av]age1 #dj miles p] h\r b dur+ ea* h\r its spe$ may rise & fall4 #b4 ,v>iable4--,a body has v>iable motion :5 its spe$ or direction ( motion is cont9ually *ang+4 ,mo/ bodies h v>iable motion4 #c4 ,accel]at$4--,a body has accel]at$ motion :5 its spe$ or direction ( motion cont9ually *anges4 ,if ! spe$ *anges by ! same am\nt ea* second1 & ! direction ( motion does n *ange ! motion is said to be uni=mly accel]at$1 e4g41 a fall+ body4 ,uni=mly accel]at$ motion w be /udi$ fur!r "u ! topic ( fall+ bodies4 ,velocity is ! rate ( motion ( a body 9 a giv5 direction4 ,= example1 a bullet may h a velocity ( #acjj ft4 a second upw>ds4 ,accel]ation is ! rate ( *ange ( velocity 9 a giv5 direction1 or ! *ange ( velocity 9 a unit ( "t4 ,a tra9 />t+ f a /ation gradually increases its spe$4 ,! ga9 9 velocity dur+ "o second is its accel]ation4 ,:5 ! velocity is decreas+1 z :5 a tra9 is sl[+ d[n1 ! accel]ation is opposite 9 direction to ! velocity4 ,a fall+ body falls fa/] & fa/]4 ,x has d[nw>d accel]ation4 ,a ball ?r[n upw>d goes m & m sl[ly4 ,x also has d[nw>d accel]ation4 #gf4 ,mom5tum4--,x is a matt] ( common obs]vation t a heavy body is set 9 motion ) m difficulty ?an a light "o1 or if ! same =ce is us$ = ! same l5g? ( "t ^u a light & a heavy body1,e ! light body w be giv5 a great] velocity4 ,?is obs]vation has l$ to ! calculation ( :at is call$ ! quantity ( motion ( a body1 or its mom5tum4 ,x is comput$ by multiply+ ! mass by ! velocity4 ,if ! ,c4,g4,s4 sy/em is us$ we %all h z ! mom5tum ( a #ab g4 body mov+ #be cm4 a second a mom5tum ( #ab #be or #cjj ,c4,g4,s4 units ( mom5tum4 ,?is unit has no "n & is !re=e express$ z indicat$ above4 ,! =mula = comput+ mom5tum is3 ,m mv4 ,e ,by a light body is meant "o ( small mass1 a heavy body possess+ mu* great] mass4 ,newton's ,laws ( ,motion #gg4 ,in]tia1 ,fir/ ,law ( ,motion4--,"o (t5 obs]ves :5 rid+ 9 a tra9 t if ! tra9 moves =w>d sudd5ly ! pass5g]s d n get into motion z soon z ! tra91 & app>5tly are j]k$ backw>d4 ,:ile if ! tra9 is /opp$ sudd5ly1 ! pass5g]s t5d to keep 9 motion4 ,?is t5d5cy ( matt] to keep mov+ :5 9 motion & to rema9 at re/ :5 at re/ is (t5 ref]r$ to z ! prop]ty ( in]tia4 ,newton's fir/ law ( motion1 (t5 call$ ! law ( in]tia1 describes ?is prop]ty ( matt] z foll[s3 ,e body cont9ues 9 a /ate ( re/ or ( uni=m motion 9 a /raight l9e unless x is compell$ to *ange t /ate by "s ext]nal =ce4 ,?is means t if an object l a book is ly+ on a table x w rema9 !re until remov$ by "s outside =ce4 ,no inanimate object c move itself or /op itself4 ,if a ball is ?r[n into ! air x w\ld move on =ev] if x 7 n = ! =ce ( attraction ( ! e>? & ! resi/ance ( ! air4 ,x takes "t to put a mass into motion1 a heavy object requir+ m "t = a *ange ?an a light object4 ,z an example ( ?is1 note ! movem5ts ( pass5g]s 9 a /reet c> :5 x />ts or /ops sudd5ly4 ,ano!r illu/ration ( ! law ( in]tia is ! s-call$ p5ny & c>d exp]im5t4 ,balance a c>d on ! end ( a f+]4 ,place on x a co9 directly ov] ! f+]1 snap ! c>d quickly s z to drive ! c>d f b5ea? ! co94 ,! co9 w rema9 on ! f+]4 7,see ,fig4 #ei47 ,illu/ration3 ,,fig4 #ei4--,! ball rema9s :5 ! c>d is driv5 away4 ,accord+ to ,newton's fir/ law ( motion a mov+ body :i* c\ld be entirely fre$ f ! action ( all ext]nal =ces w\ld h uni=m motion1 & w\ld describe a p]fectly /raight c\rse4 ,! curv$ pa? tak5 by a baseball :5 ?r[n %[s t x is act$ ^u by an outside =ce4 ,?is =ce1 ! attraction ( ! e>?1 is call$ gravity4 ,illu/ration3 ,,sir ,,isaac ,,newton ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,sir ,isaac ,newton 7#afdb-agbg7 ,pr(essor ( ma!matics at ,cambridge univ]sity2 discov]$ gravitation2 inv5t$ calculus2 ann\nc$ ! laws ( motion2 wrote ! ,pr9cipia2 made _m discov]ies 9 light4 ,illu/ration3 ,,galileo ,,galilei ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,galileo ,galilei 7#aefd-afdb74 ,italian4 ,f\nd] ( exp]im5tal sci5ce2 ,orig9ator ( mod]n physics2 made ! fir/ !rmomet]2 discov]$ ! laws ( fall+ bodies & ! laws ( ! p5dulum2 inv5t$ ,galilean telescope4 ,illu/ration3 ,,fig4 #fj4--;,cross-section ( ! ,de,laval cream sep>ator4 #gh4 ,curvil9e> ,motion4--,curvil9e> motion occurs :5 a mov+ body is pull$ or pu%$ away f a /raight pa?4 ,! pull or pu% is call$ c5tripetal 7c5t]-seek+7 =ce4 ,a mov+ /one on ! end ( a /r+ :5 pull$ t[>d ! h& moves 9 a curve4 ,if ! /r+ is releas$ ! /one moves 9 a tang5t to ! curve4 ,! /r+ pulls ! h&4 ,?is phase ( ! pull is call$ c5trifugal =ce4 ,! c5tripetal =ce is ! pull on ! /one4 ,c5tripetal & c5trifugal =ce toge!r cause a t5sion 9 ! /r+4 ,examples ( curvil9e> motion are v common4 ,! rid] & horse 9 a circus r+ lean inw>d 9 ord] to move 9 a curve4 ,! curve on a runn+ track 9 a gymnasium is bank$ = ! same reason4 ,mud fly+ f ! :eel ( a c>riage1 ! skidd+ ( an automobile :5 pass+ rapidly ar\nd a corn]1 & sp>ks fly+ f an em]y :eel1 are illu/rations ( ! ,fir/ ,law ( ,motion4 ,cream is sep>at$ f milk by plac+ ! :ole milk 9 a rapidly revolv+ b[l1 ! cream be+ light] collects 9 ! c5t] & is ?r[n (f at ! top4 7,see ,fig4 #fj47 ,clo!s 9 /eam laundries are dri$ by a c5trifugal dri]4 ,9 amusem5t p>ks _m devices use ?is pr9ciple4 7,see c5trifugal pumps1 ,art4 #gj47 ,illu/ration3 ,,fig4 #fa4--,! two balls rea* ! floor at ! same "t4 #gi4 ,! ,second ,law ( ,motion1 sometimes call$ ! law ( mom5tum1 leads to ! measurem5t ( =ce1 by ! mom5tum or ! quantity ( motion1 produc$ by x4 ,! law is /at$ z foll[s3 ,*ange ( motion1 or mom5tum1 is proportional to ! act+ =ce & takes place 9 ! direction 9 :i* ! =ce acts4 ,9 o!r words1 if two or m =ces act at ! same in/ant ^u a body ea* produces ! same effect t x w\ld if act+ alone4 ,if a c>d be support$ on two nails driv5 horizontally close toge!r into an upright bo>d 7see ,fig4 #fa71 & two m>bles be s plac$ on ! ends z to balance ea* o!r1 :5 "o m>ble is snapp$ horizontally by a bl[1 ! o!r w fall4 ,bo? rea* ! floor at ! same "t4 ,! two balls are equally pull$ d[n by ! e>?'s attraction & /rike ! gr\nd at ! same "t1 ?\gh "o is %ot sidewise1 & ! o!r is dropp$ v]tically4 ,z gravity is a con/ant =ce1 :ile ! bl[ 0 only a mom5t>y =ce1 ! actual pa? or resultant motion w be a curv$ l9e4 ,! con/ant relation1 betwe5 ! act+ =ce & ! *ange ( mom5tum x produces 9 a body1 has l$ to ! adoption ( a conv5i5t ,c4,g4,s4 unit ( =ce call$ ! dyne4 ,! dyne is t =ce :i* c imp>t to a mass ( "o gram a *ange ( velocity at ! rate ( "o c5timet] p] second e second4 ,?is def9ition assumes t ! body act$ ^u is free to move )\t h9drance ( any k9d1 s t ! act+ =ce has to ov]come only ! in]tia ( ! body4 ,h[ev]1 ! law applies 9 e case ( application ( =ce1 s t ea* =ce produces its full effect indep5d5tly ( o!r =ces t may be act+ at ! same "t ^u ! body4 #hj4 ,newton's ,?ird ,law4--,?is law has be5 exp]i5c$ by ev]yone :o has jump$ f a r[boat ne> ! %ore4 ,! muscul> action t pu%es ! body =w>d f ! boat also pu%es ! boat backw>d1 (t5 ) awkw>d results4 ,! law is /at$3 ,to e action1 !re is always an opposite & equal reaction1 or ! mutual actions ( any two bodies are always equal & opposite 9 direction4 ,_m illu/rations ( ?is law are 9 e "o's m9d3 a /ret*$ rope pulls ) ! same =ce 9 "o direction z x does 9 ! opposite direction4 ,if a bat hits a ball1 ! ball hits ! bat ) an equal & opposite =ce4 ,! ?ird law is !re=e sometimes call$ ! law ( reaction4 ,:5 a weight is hung ^u a spr+ balance ! action ( ! weight pulls d[n ! spr+ until x has /ret*$ suffici5tly 7,hooke's ,law7 to produce an ela/ic reaction t equals & h5ce supports ! weight4 ,:5 a man /&s at ! c5t] ( a plank support$ at its ends1 ! action ( ! man's weight b5ds ! plank until ! ela/ic =ce develop$ 9 ! plank equals ! weight appli$4 ,fur!r1 :5 a tra9 or a wagon is on a bridge ! bridge yields until x has develop$ an ela/ic reaction equal to ! weight appli$4 ,if a p]son /&s 9 ! c5t] ( a room1 ! floor beams yield until ! ?ird law is satisfi$4 ,9 fact1 :5ev] a =ce acts1 a contr>y equal =ce always acts4 #ha4 ,/ress & ,/ra94--,a pair ( =ces t con/itute an action & a reaction is call$ a /ress4 ,! two =ces are two p>ts ( "o /ress4 ,if ! two =ces act away f ea* o!r1 z 9 ! break+ ( a /r+1 ! /ress is call$ a t5sion1 b if !y act t[>d ea* o!r z 9 cru%+ any?+1 ! /ress is call$ a pressure4 ,9 ord] = a body to ex]t =ce x mu/ meet ) resi/ance4 ,! =ce ex]t$ is nev] great] ?an ! resi/ance enc\nt]$4 ,?us "o c ex]t b little =ce ^u a fea!r float+ 9 ! air or ^u o!r light objects4 ,a fa/ mov+ %ot ex]ts no =ce unless x enc\nt]s "s resi/ance4 ,=ces1 !n1 are always f\nd 9 pairs4 ,?us to break a /r+1 to /ret* an ela/ic b&1 to squeeze a lemon1 "o mu/ ex]t two equal & opposite =ces4 ,su* a ?+ z a s+le =ce act+ alone is unkn[n4 ,usually1 h[ev]1 we give our att5tion ma9ly to "o ( ! =ces & ignore ! o!r4 ,:5 a =ce acts ^u a body ! *ange ( %ape or size result+ is call$ a /ra94 ,hooke's law 7,art4 #cb7 is (t5 express$ z foll[s3 ,! /ra9 is proportional to ! /ress1 e4g41 ! /ret* ( ! spr+ ( a spr+ balance is proportional to ! load plac$ ^u x4 ,important ,topics #a4 ,motion a *ange ( position4 ,k9ds ( motion4 #b4 ,newton's laws ( motion4 #c4 ,mom5tum4 #d4 ,in]tia4 ,fir/ law ( motion4 ,curvil9e> motion4 #e4 ,second law ( motion4 #f4 ,?ird law ( motion4 ,action & reaction1 /ress & /ra94 ,ex]cises #a4 ,m5tion ?ree illu/rations ( ! ?ird law1 diff]5t f ^? giv54 #b4 ,a rifle bullet ?r[n aga9/ a bo>d /&+ ^u edge w knock x d[n2 ! same bullet fir$ at ! bo>d w pass ?r\gh x )\t di/urb+ its position4 ,expla94 #c4 ,a hamm] is (t5 driv5 on to its h&le by /rik+ ! end ( ! latt]4 ,expla94 #d4 ,consid] a tra9 mov+ #fj miles an h\r1 ) a gun on ! re> plat=m po9t+ /raight backw>d4 ,if a ball is fir$ f ! gun ) a spe$ ( #fj miles an h\r1 :at w happ5 to ! ball8 #e4 ,c\ld "o play ball on ! deck ( an ocean /eam] go+ #be miles an h\r )\t mak+ all[ance = ! motion ( ! %ip8 ,expla94 #f4 ,on a railroad curve1 "o rail is always high]4 ,:i*8 ,:y8 #g4 ,:y c a small boy :5 *as$ by a big boy (t5 escape by dodg+8 #h4 ,w a /one dropp$ f a mov+ tra9 fall 9 a /raight l9e8 ,expla94 #i4 ,a bla/ ( f9e s& driv5 aga9/ a %eet ( glass soon gives x a r\gh surface4 ,expla94 #aj4 ,expla9 ! use ( fly-:eels 9 /eady+ ! motion ( ma*9]y 7= example1 ! sew+ ma*9e74 #aa4 ,is x easi] to walk to ! front or re> ( a pass5g] tra9 :5 x is /opp+8 ,:y8 #ab4 ,:y does l[]+ ! h&les ( a :eel-b>r[ on ! in/ant ( /rik+ make x easi] to g ov] a bump8 #ac4 ,:y %\ld a /rong side w9d int]f]e ) a game ( t5nis8 ,h[ c x be all[$ =8 #ad4 ,on :i* side ( a railroad track at a curve is x ! saf] to walk :ile a tra9 is pass+8 ,:y8 #ae4 ,:y does a bullet :5 fir$ ?r\gh a w9d[ make a clean r\nd hole 9 ! glass1 :ile a small /one ?r[n aga9/ ! w9d[ %att]s ! glass8 #af4 ,a tall[ c&le c be fir$ ?r\gh a p9e bo>d4 ,:y8 #ag4 ,9 cyclones1 /raws are frequ5tly f\nd driv5 a little di/ance into trees2 :y are ! /raws n brok5 & cru%$ in/ead ( be+ driv5 into ! tree unbrok58 #ah4 ,a bullet weigh+ "o-half oz4 is fir$ f a gun weigh+ #h lb4 ,! bullet has a velocity ( #ahjj ft4 p] second4 ,f9d ! velocity ( ! kick or recoil ( ! gun4 #ah4 ,:5 football play]s run into ea* o!r :i* "o is ?r[n ! h>d]8 ,:y8 #bj4 ,a railroad tra9 weigh+ #djj tons has a velocity ( #fj miles p] h\r4 ,an ocean /eam] weigh+ #bj1jjj tons has a velocity ( "o half mile p] h\r4 ,h[ d _! mom5ta comp>e8 #ba4 ,:y is a heavy boy pref]able to a light] weight boy = a football team8 #bb4 ,:y does a blacksmi? :5 he desires to /rike a heavy bl[1 select a heavy sl$ge hamm] & sw+ x ov] 8 head8 #bc4 ,:y does ! cat*] on a baseball team we> a padd$ glove8 7#c7 ,,resolution ,,( ,,=ces #hb4 ,resolution ( ,=ces4--,we h be5 /udy+ ! effect ( =ces 9 produc+ motion & ! results ( comb9+ =ces 9 _m ways2 9 ! same l9e1 9 p>allel l9es1 & 9 div]g+ l9es4 ,ano!r case ( mu* int]e/ & importance is ! det]m9ation ( ! effectiv5ess ( a =ce 9 a direction diff]5t f ! "o 9 :i* x acts4 ,?is case :i* is call$ resolution ( =ces is frequ5tly us$4 ,to illu/rate3 "o ne$s b to recall t a sailor uses ?is pr9ciple 9 a practical way :5ev] he sails 8 boat 9 any o!r direction ?an ! "o 9 :i* ! w9d is bl[+1 e4g41 :5 ! w9d is bl[+1 say f ! nor?1 ! boat may be driv5 ea/1 we/1 or to any po9t s\? betwe5 ! ea/ & we/ & x is ev5 possible to beat back aga9/ ! w9d t[>d ! nor!a/ or nor?we/4 ,take a sl$ drawn by a %ort rope ) ! =ce appli$ along ! l9e ,,ab 7see ,fig4 #fb72 "p ( ?is =ce t5ds to lift ! front ( ! sl$ z ,,ac & a "p to draw x =w>d z ,,ad4 ,h5ce n all ( ! =ce appli$ along ,,ab is us$ 9 draw+ ! sl$ =w>d4 ,its effectiv5ess is indicat$ by ! relative size ( ! compon5t ,,ad comp>$ to ,,ab4 ,illu/ration3 ,,fig4 #fb4--;,,ad is ! effective compon5t4 ,! =ce ( gravity act+ ^u a sph]e t is re/+ on an incl9$ plane may be readily resolv$ into two compon5ts1 "o1 ! effective compon5t1 z ,,or1 & ! o!r1 ! non-effective z ,,os4 7,see ,fig4 #fc47 ,if ! angle ,,acb is #cj degrees1 ,,ab equals #a_/b ( ,,ac & ,,or equals #a_/b ( ,,og1 s t ! spe$ ( ! sph]e d[n ! plane develop$ 9 #a second is less ?an 7ab\t "o-half (7 ! spe$ ( a freely fall+ body develop$ 9 ! same "t4 ,:y is ,,os non-effective8 ,illu/ration3 ,,fig4 #fc4--,! effective compon5t is ,,or4 ,illu/ration3 ,,fig4 #fd4--,resolution ( ! =ces act+ on an a]oplane4 #hc4 ,! ,a]oplane4--,! a]oplane consi/s ( "o or two frames ,,abcd 7see ,fig4 #fd71 ov] :i* is /ret*$ clo? or ?9 %eet metal4 ,x is driv5 ?r\gh ! air by a propell] turn$ by a p[]ful gasol9e motor4 ,?is has ! effect ( creat+ a /rong breeze com+ t[>d ! front ( ! a]oplane4 ,z 9 ! case ( ! sailboat a pressure is creat$ at "r angles to ! plane along ,,gf & ?is may be resolv$ into two compon5ts z ,,gc & ,,ge1 ,,gc act+ to lift ! a]oplane v]tically & ,,ge oppos+ ! action ( ! propell]4 ,fig4 #fe repres5ts ! ,curtis ,fly+ ,boat pass+ ov] ! ,detroit riv]4 ,illu/ration3 ,,fig4 #fe4--,! ,curtis hydroplane4 ,ex]cises4 #a4 ,if a wagon weigh+ #djjj lbs4 is ^u a hill :i* rises #a ft4 9 #f1 :at =ce p>allel to ! hill w j support ! load8 7,f9d ! effective compon5t ( ! weight d[n ! hill47 #b4 ,if a b>rel is be+ roll$ up a #af-;ft4 ladd] into a wagon box #c ft4 f ! gr\nd1 :at =ce w hold ! b>rel 9 place on ! ladd]1 if ! b>rel weighs #bdj lbs4 ,%[ by diagram4 #c4 ,%[ graphically ! compon5ts into :i* a man's pu% ^u ! h&le ( a lawn m[] is resolv$4 #d4 ,does a man %oot+ a fly+ duck aim at ! bird8 ,expla94 #e4 ,:at are ! ?ree =ces t act on a kite :5 x is /&+ 9 ! air8 #f4 ,:at relation does ! resultant ( any two ( ! =ces 9 problem five h to ! ?ird8 #g4 ,into :at two =ces is ! weight ( a wagon desc5d+ a hill resolv$8 ,expla9 by use ( a diagram4 #h4 ,a w9d /rikes ! sail ( a boat at an angle ( #fj degrees to ! p]p5dicul> ) a pressure ( #c lbs4 p] squ>e foot4 ,:at is ! effective pressure1 p]p5dicul> to ! sail8 ,:at w\ld be ! effective pressure :5 x /rikes at #cj degrees8 #i4 ,h[ is ! v]tical compon5t ( ! =ce act+ on an a]oplane affect$ :5 ! front edge ( ! plane is elevat$8 ,%[ by diagram4 7#d7 ,,mom5t ,,( ,,=ce ,,& ,,p>allel ,,=ces #hd4 ,mom5t ( ,=ce4--,9 ! /udy ( motion we f\nd t ! quantity ( motion is call$ mom5tum & is measur$ by ! product ( ! mass times ! velocity4 ,9 ! /udy ( p>allel =ces1 especially su* z t5d to produce rotation1 we consid] a simil> quantity4 ,x is call$ a mom5t ( =ce1 :i* is ! t]m appli$ to ! effectiv5ess ( a =ce 9 produc+ *ange ( rotation4 ,x also measur$ by ! product ( two quantities2 ,"o1 ! magnitude ( ! =ce itself1 & ! o!r1 ! p]p5dicul> di/ance f ! axis ab\t :i* ! rotation takes place to ! l9e repres5t+ ! direction ( ! =ce4 ,illu/ration3 ,,fig4 #ff4--,! mom5ts ab\t ,s are equal4 ,to illu/rate3 ,take a rod1 z a met] /ick1 drill a hole at ,s & place ?r\gh x a screw fa/5$ at ! top ( ! blackbo>d4 ,atta* by cords two spr+ balances & draw to ! "r & left1 ,a & ,b z 9 ,fig4 #ff4 ,draw out ! balance ,b ab\t half way1 hold x /eadily1 or fa/5 ! cord at ! side ( ! blackbo>d1 & read bo? balances4 ,note also ! di/ance ,,z & ,,bs4 ,s9ce ! rod is at re/1 ! t5d5cy to rotate to ! "r & left mu/ be equal4 ,t is1 ! mom5ts ( ! =ces at ,a & ,b ab\t ,s are equal4 ,s9ce ^! are comput$ by ! product ( ! =ce times ! =ce arm1 multiply ,b by ,,bs & ,a by ,,z & see if ! comput$ mom5ts are equal4 ,h5ce a =ce t t5ds to turn or rotate a body to ! "r c be balanc$ by ano!r ( equal mom5t t acts t[>d ! left4 ,illu/ration3 ,,fig4 #fg4--,law ( p>allel =ces illu/rat$4 #he4 ,p>allel ,=ces4--,objects are frequ5tly support$ by two or m upw>d =ces act+ at diff]5t po9ts & =m+ 9 ?is way a sy/em ( p>allel =ces2 z :5 two boys c>ry a /r+ ( fi% on a rod betwe5 !m or :5 a bridge is support$ at its ends4 ,! pr9ciple ( mom5ts j describ$ aids 9 det]m9+ ! magnitude ( su* =ces & ( _! resultant4 ,to illu/rate ?is take a wood5 bo>d #d 94 wide & #d ft4 long ( uni=m dim5sions4 7,see ,fig4 #fg47 ,place sev]al screw hooks on "o edge ) "o set at ,o :]e ! bo>d w hang horizontally :5 ! bo>d is susp5d$ !re4 ,weigh ! bo>d by a spr+ balance hung at ,o4 ,?is w be ! resultant 9 ! foll[+ te/s4 ,n[ hang ! bo>d f two spr+ balances at ,m & ,n & read bo? balances4 ,call read+s f & f4 ,to te/ ! =ces consid] ,m z a fix$ po9t 7see ,fig4 #fg7 & ! weight ( ! bo>d to act at ,o4 ,!n ! mom5t ( ! weight ( ! bo>d %\ld be equal ! mom5t ( ! =ce at ,n s9ce ! bo>d does n move1 or w times ,,om equals f times ,,nm4 ,if ,n is consid]$ ! fix$ po9t !n ! mom5t ( ! weight ( ! bo>d & ( f ) ref]5ce to ! po9t ,n %\ld be equal1 or w times ,,on f times ,,nm4 ,keep+ ?is illu/ration 9 m9d1 ! law ( p>allel =ces may be /at$ at foll[s3 #a4 ,! resultant ( two p>allel =ces act+ 9 ! same direction at diff]5t po9ts 9 a body is equal to _! sum & has ! same direction z ! compon5ts4 ,! mom5t ( "o ( ! compon5ts ab\t ! po9t ( application ( ! o!r is equal & opposite to ! mom5t ( ! support$ weight ab\t ! o!r4 ,problem4--,if two boys c>ry a /r+ ( fi% weigh+ #dj lbs4 on a rod #h ft4 long betwe5 !m1 :at =ce mu/ ea* boy ex]t if ! /r+ is #e ft4 f ! re> boy8 ,solution4--,! mom5t ( ! =ce ,f ex]t$ ab\t ! opposite end by ! re> boy is ,f #h4 ,! mom5t ( ! weight ab\t ! same po9t is #dj 7#h - #e7 #abj4 ,!re=e ,f #h #abj1 or ,f #ae1 ! =ce ex]t$ by ! re> boy4 ,! front boy ex]ts a =ce ( ,f ^: mom5t ab\t ! o!r end ( ! rod is ,f #h4 ,! mom5t ( ! weight ab\t ! same po9t is #dj #e #bjj4 ,s9ce ! mom5t ( ,f equals ?is1 #bjj ,f #h1 or ,f #be4 ,h5ce ! front boy ex]ts #be lbs4 & ! re> boy #ae lbs4 ,illu/ration3 ,,fig4 #fh4--;,a c\ple4 #hf4 ,! ,c\ple4--,if two equal p>allel =ces act ^u a body along diff]5t l9es 9 opposite directions1 z 9 ,fig4 #fh1 !y h no s+le resultant or !re is no "o =ce t w h ! same effect z ! two compon5ts act+ toge!r4 ,a comb9ation ( =ces ( ?is k9d is call$ a c\ple4 ,its t5d5cy is to produce *ange ( rotation 9 a body4 ,an example is ! action ^u a compass ne$le :i* is rotat$ by a =ce :i* urges "o end t[>d ! nor? & by an equal =ce :i* urges ! o!r end t[>d ! s\?4 ,important ,topics #a4 ,mom5t ( =ce1 h[ measur$4 #b4 ,p>allel =ces4 #c4 ,! two laws ( p>allel =ces4 #d4 ,! c\ple4 ,ex]cises #a4 ,%[ by diagram h[ to arrange a ?ree-horse ev5] s t ea* horse mu/ take "o-?ird ( ! load4 #b4 ,two boys support a #aj-;ft4 pole on _! %\ld]s ) a #dj-lb4 /r+ ( fi% support$ f x #d ft4 f ! front boy4 ,:at load does ea* boy c>ry8 ,"w by pr9ciple ( mom5ts4 #c4 ,if two horses draw a load ex]t+ a comb9$ pull ( #cjj lbs41 :at =ce mu/ ea* ex]t if "o is #bh 94 & ! o!r is #cb 94 f ! po9t ( atta*m5t ( ! ev5] to ! load8 ,illu/ration3 ,,fig4 #fi4--;,=ces act+ ^u a /ret*$ rope4 ,illu/ration3 ,,fig4 #gj4--;,a crane ) horizontal tie4 #d4 ,a weight ( #ajj lbs4 is susp5d$ at ! middle ( a rope ,,acb #bj ft4 long4 7,see ,fig4 #fi47 ,! ends ( ! rope are fa/5$ at po9ts ,a & ,b at ! same height4 ,consid] ,d z ! c5t] ( ! l9e ,,ab4 ,:at is ! t5sion ( ! rope :5 ,,cd is #c ft48 ,:5 ,,cd is #a ft48 ,:5 ,,cd is #a 948 #e4 ,a crane is set up ) ! tie horizontal4 7,see ,fig4 #gj47 ,if #ajjj lbs4 is to be lift$1 f9d ! tie /ress & ! boom /ress if ! boom angle is #cj degrees8 ,if #de degrees8 #fj degrees8 #f4 ,a ball is plac$ on a plane incl9$ at an angle ( #cj degrees to ! horizontal4 ,:at fraction ( its weight t5ds to cause motion d[n ! plane8 ,:at effect does ! o!r compon5t ( ! weight h8 ,:y8 #g4 ,a p]son weigh+ #aej lbs4 is ly+ 9 a hammock4 ,! di/ance betwe5 ! supports is #ae ft4 ,! hammock sags #d ft4 ,:at is ! t5sion 9 ! supports at ea* end8 ,:at is ! t5sion :5 ! sag is only #a ft48 #h4 ,a ladd] #cj ft4 long & weigh+ #hj lbs4 leans aga9/ ! side ( a build+ s t x makes an angle ( #cj degrees ) ! build+4 ,f9d ! direction & magnitude ( ! compon5t =ces on ! gr\nd & at ! build+4 #i4 ,a travel+ crane #ej ft4 long weigh+ #aj tons moves f "o end ( a %op to ! o!r1 at ! same "t a load ( #djjj lbs4 moves f end to end ( ! crane4 ,f9d ! pressure ( ! trucks ( ! crane on ! track :5 ! load is at a di/ance ( #e1 #aj1 #ae1 & #be ft4 f ei!r end4 ,illu/ration3 ,,fig4 #ga--;,a truss4 #aj4 ,resolve a =ce ( #ejj lbs4 into two compon5ts at "r angles to ea* o!r1 "o ( :i* %all be f\r times ! o!r4 #aa4 ,a truss 7see ,fig4 #ga71 c>ries a load ( #ajjj lbs4 at ,c4 ,f9d ! =ces act+ along ,,ac1 ,,bc1 & ,,ab4 ,if ,,ac & ,,bc are ea* #ab ft4 & ,,ab #bj ft41 :i* ( ^! =ces are t5sions & :i* are pressures8 7#e7 ,,gravitation ,,& ,,gravity #hg4 ,gravitation4--,gravitation is ! =ce ( attraction t exi/s betwe5 all bodies ( matt] at all di/ances4 ,?is attraction exi/s n only betwe5 ! heav5ly bodies1 ! />s & planets1 etc41 b is also f\nd betwe5 bodies on ! e>?4 ,a book attracts all objects 9 a room & outside ( a room z well1 s9ce its weight %[s t x is attract$ by ! e>? itself4 ,! gravitational attraction betwe5 ord9>y bodies is s slight t x requires c>eful exp]im5ts to detect x4 ,9 fact1 x is only :5 "o ( ! attract+ bodies is l>ge1 z = example ! e>?1 t ! =ce becomes consid]able4 ,c>eful /udies ( ! motions ( ! heav5ly bodies1 especially ( t ( ! moon 9 its orbit ab\t ! e>?1 l$ ,sir ,isaac ,newton to ! /atem5t ( ! law ( gravitation :i* is well express$ 9 ! foll[+ /atem5t3 #hh4 ,law ( ,gravitation4--,e p>ticle ( matt] 9 ! univ]se attracts e o!r p>ticle ) a =ce t is directly proportional to ! product ( _! masses & inv]sely proportional to ! squ>e ( ! di/ance betwe5 !m4 ,! law may be sep>at$ into two p>ts1 "o ref]r+ to ! masses ( ! bodies conc]n$1 ! o!r to ! effect ( ! di/ance betwe5 !m4 ,! fir/ "p is easily und]/ood s9ce we all "k t two qu>ts ( milk w weigh j twice z mu* z "o qu>t4 ,to illu/rate ! second "p ( ! law1 suppose t ! moon 7 remov$ to twice its pres5t di/ance f ! e>?1 !n ! attraction betwe5 ! e>? & ! moon w\ld be "o-f\r? its pres5t attraction4 ,if remov$ to ?ree times its pres5t di/ance1 ! attraction w\ld be "o-n9?1 etc4 ,! attraction ( ! e>? = o!r bodies on or ne> x is call$ gravity4 ,! weight ( a body is ! measure ( ! e>?'s attraction = x2 or x is ! =ce ( gravity act+ ^u x4 ,newton's ?ird law ( motion /ates t e action is accompani$ by an equal & opposite reaction 7,art4 #hj74 ,h5ce1 ! attraction ( ! e>? = a book or any o!r object is accompani$ by an equal attraction ( ! book = ! e>?4 #hi4 ,weight4--,9 advanc$ physics x is prov$ t a sph]e attracts z if x 7 conc5trat$ at its c5t]4 ,?us if ! e>?'s radius be consid]$ z #djjj miles1 !n a body #djjj miles above ! e>?'s surface w\ld be #hjjj miles above ! e>?'s c5t]1 or twice z f> f ! c5t] ( ! e>? z is a body ^u ! e>?'s surface4 ,a body !n #djjj miles above ! e>?'s surface w weigh !n b "o-f\r? z mu* z x w at ! surface ( ! e>?4 ,s9ce ! e>? is flatt5$ at ! poles1 ! surface at ! equator is f>!r f ! c5t] ( ! e>? ?an at po9ts nor? or s\?4 ,?us a body weigh+ #a lb4 at ! equator weighs #a4jjb lb4 at ,*icago1 or ab\t #a_/ejj m4 ,! rotation ( ! e>? also affects ! weight ( a body ^u x s t at ! equator ! weight ( a body is #a_/bhi less ?an at ! pole4 ,bo? effects1 t ( flatt5+ & ( rotation1 t5d to dim9i% ! weight ( bodies at ! equator1 s t a body at ! latt] place weighs ab\t #a_/aib less ?an at ! poles4 ,9 /udy+ ! effect ( ! e>?'s gravity1 ! foll[+ illu/ration w be helpful3 ,imag9e an op5 %aft a mile squ>e ext5d+ ?r\gh ! e>?4 ,:at w\ld happ5 to a /one ?r[n into ! %aft8 ,at fir/ x w\ld h ! attraction ( ! :ole e>? draw+ x & cont9ually increas+ its spe$ d[nw>d4 ,z x desc5ds f ! surface1 ! pull t[>d ! c5t] gr[s less & less4 ,halfway to ! c5t] ! body has lo/ half its weight4 ,:5 ! /one rea*es ! c5t]1 ! pull 9 all directions is ! same1 or 9 o!r words1 x has no weight4 ,x w\ld1 h[ev]1 cont9ue mov+ rapidly on acc\nt ( its in]tia1 & z x cont9ues on f ! c5t]1 ! great] "p ( ! e>? be+ left beh9d1 ! attraction pull+ t[>d ! c5t] w gradually /op x4 ,x w !n fall aga9 t[>d ! c5t] & be /opp$ aga9 aft] pass+ x1 & aft] repeat$ly mov+ up & d[n w f9ally come to re/ at ! c5t] ( ! e>?4 ,at ?is po9t x w be f\nd to be a body )\t weight s9ce x is pull$ equally 9 all directions by ! mat]ial ( ! e>?4 ,:at =ce br+s ! body to re/8 #ij4 ,c5t] ( ,gravity4--,a body is compos$ ( a great _m p>ticles ea* ( :i* is pull$ t[>d ! c5t] ( ! e>? by ! =ce ( gravity4 ,a s+le =ce t w\ld exactly equal ! comb9$ effect ( ! pull ( ! e>? = all ! p>ticles ( a body w\ld be _! resultant4 ,! magnitude ( ?is resultant is ! weight ( ! body4 ,! direction ( ?is resultant is 9 a l9e pass+ t[>d ! e>?'s c5t]1 :ile ! po9t ( application ( ?is resultant is call$ ! c5t] ( gravity ( ! body4 ,! c5t] ( gravity ( a body may also be briefly def9$ z ! po9t ab\t :i* x may be balanc$4 ,z ! location ( ?is po9t dep5ds ^u ! di/ribution ( matt] 9 ! body1 ! c5t] ( gravity is also sometimes call$ ! c5t] ( mass ( ! body4 ,! e>?'s attraction = a body is consid]$ = ! sake ( simplicity1 n z a multitude ( little =ces1 b z a s+le =ce appli$ at its c5t] ( gravity4 ,to f9d ! c5t] ( gravity ( a body f9d two int]sect+ l9es along :i* x balances1 see ,fig4 #gb1 & ! c5t] ( gravity w be at ! int]section4 ,a v]tical l9e ?r\gh ?is po9t is sometimes call$ ! l9e ( direction ( ! weight4 ,illu/ration3 ,,fig4 #gb4--,! c5t] ( gravity is at ! int]section ( ! l9es ( direction4 #ia4 ,equilibrium ( ,bodies4--,equilibrium means equally balanc$4 ,a body at re/ or 9 uni=m motion is !n 9 equilibrium4 ,an object is 9 equilibrium "u gravity :5 a v]tical l9e ?r\gh its c5t] ( gravity passes ?r\gh ! po9t ( support4 ,a trunk is an example ( a body 9 equilibrium s9ce a v]tical l9e f its c5t] ( gravity falls )9 ! base =m$ by ! area ^u :i* x re/s4 ,"w w be necess>y to tip ! trunk f its position4 ,! am\nt ( "w requir$ w dep5d ^u ! weight ( ! body & ! location ( ! c5t] ( gravity4 #ib4 ,k9ds ( ,equilibrium4--7a7 ,/able4--,a body is 9 /able equilibrium "u gravity if its c5t] ( gravity is rais$ :5ev] ! body is displac$4 ,x w return to its fir/ position if all[$ to fall aft] be+ slightly displac$4 ,9 ,fig4 #gc1 a & b if slightly tipp$ w return to _! fir/ position4 ,!y are 9 /able equilibrium4 ,o!r examples are a rock+ *air1 & ! comb9ation %[n 9 ,fig4 #gd4 ,illu/ration3 ,,fig4 #gc4--,/able equilibrium4 7b7 ,un/able4--,a body is 9 un/able equilibrium "u gravity if its c5t] ( gravity is l[]$ :5ev] ! body is slightly displac$4 ,x w fall f>!r f its fir/ position4 ,a p5cil balanc$ on its po9t or a broom balanc$ on ! end ( ! h&le are 9 un/able equilibrium4 ,! slighte/ di/urbance w make ! l9e ( direction ( ! weight fall outside ( 7away f7 ! po9t ( support 7,fig4 #ge a74 ,illu/ration3 ,,fig4 #gd--;,an example ( /able equilibrium4 ,:y8 ,illu/ration3 ,,fig4 #ge4--,un/able equilibrium a1 neutral equilibrium b4 7c7 ,neutral4--,a body is 9 neutral equilibrium if its c5t] ( gravity is nei!r rais$ nor l[]$ :5ev] ! body is mov$4 ,famili> examples are a ball ly+ on a table 7,fig4 #ge b7 & a wagon mov+ on a level /reet 7ref]r+ to its =w>d motion74 ,illu/ration3 ,,fig4 #gf4--;,b is m /able ?an ,a4 #ic4 ,/ability4--,:5 a body is 9 /able equilibrium1 ef=t mu/ be ex]t$ to ov]turn x1 & ! degree ( /ability is measur$ by ! ef=t requir$ to ov]turn x4 ,to ov]turn a body1 x mu/ be mov$ s t ! v]tical l9e ?r\gh its c5t] ( gravity w pass outside ( its support+ base4 ,?is movem5t 9 /able bodies necessitates a rais+ ( ! c5t] ( gravity4 ,! high] ?is c5t] ( gravity mu/ be rais$ 9 ov]turn+ ! body1 ! m /able x is1 e4g41 see ,fig4 #gf4 ,?us a wagon on a hillside w n ov]turn until its weight falls outside ( its base1 z 9 ,fig4 #gg ,b4 ,! /ability ( a body dep5ds ^u ! position ( its c5t] ( gravity & ! area ( its base4 ,! l[] ! c5t] ( gravity & ! l>g] ! base1 ! m /able ! body4 ,:at means are employ$ to give /ability to bodies1 9 e-day use 7su* z clocks1 ink-/&s1 pit*]s1 vases1 *airs1 lamps1 etc478 ,illu/ration3 ,,fig4 #gg4--;,b w ov]turn2 ,a w n4 ,important ,topics #a4 ,gravitation2 law ( gravitation1 gravity1 weight4 #b4 ,c5t] ( gravity4 #c4 ,! ?ree /ates ( equilibrium4 ,/ability4 ,ex]cises #a4 ,:y is a plumb-l9e useful 9 build+ h\ses8 #b4 ,:at is ! c5t] ( gravity ( a body8 #c4 ,expla9 ! action ( a rock+ *air t has be5 tipp$ =w>d4 #d4 ,is ! /ability ( a box great] :5 empty or :5 fill$ ) s&8 ,expla94 #e4 ,h[ c y />t y\rself sw++1 9 a sw+1 )\t t\*+ ! gr\nd8 #f4 ,is ! c5t] ( gravity ( ! beam ( a balance above1 bel[1 or at ! po9t ( a support8 ,h[ did y f9d x out8 #g4 ,:y are "s ink bottles cone %ap$ ) ?ick bottoms8 #h4 ,w\ld an electric fan 9 motion on ! re> ( a light boat move x8 ,w\ld x move ! boat if revolv+ "u wat]8 ,expla94 #i4 ,:at turns a rot>y lawn spr9kl]8 #aj4 ,:y1 :5 y are /&+ erect aga9/ a wall & a co9 is plac$ betwe5 y\r feet1 c y n /oop & pick x up unless y %ift y\r feet or fall ov]8 #aa4 ,:at w\ld become ( a ball dropp$ into a l>ge hole bor$ ?r\gh ! c5t] ( ! e>?8 #ab4 ,:5 an apple falls to ! gr\nd1 does ! e>? rise to meet x8 #ac4 ,h[ f> f ! e>? does ! =ce ( gravity ext5d8 #ad4 ,:y 9 walk+ up a flight ( /airs does ! body b5d =w>d8 #ae4 ,9 walk+ d[n a /eep hill :y d p frequ5tly b5d backw>d8 #af4 ,:y is x s difficult = a *ild to le>n to walk1 :ile a kitt5 or a puppy has no su* difficulty8 #ag4 ,expla9 :y ! use ( a cane by old p makes x easi] = !m to walk8 7#f7 ,,fall+ ,,bodies #id4 ,fall+ ,bodies4--,"o ( ! e>lie/ physical facts le>n$ by a *ild is t a body unsupport$ falls t[>d ! e>?4 ,:5 a *ild lets g ( a toy1 he soon le>ns to look = x on ! floor4 ,x is also ( common obs]vation t light objects1 z fea!rs & pap]1 fall mu* sl[] ?an a /one4 ,! in=mation1 !re=e1 t all bodies actually fall at ! same rate 9 a vacuum or :5 remov$ f ! ret>d+ influ5ce ( ! air is receiv$ ) surprise4 ,?is fact may be %[n by us+ :at is call$ a co9 & fea!r tube4 ,on exhau/+ ! air f ?is tube1 ! fea!r & co9 )9 are se5 to fall at ! same rate4 7,see ,fig4 #gh47 :5 air is aga9 admitt$1 ! fea!r flutt]s along beh9d4 ,illu/ration3 ,,fig4 #gh4--;,bodies fall alike 9 a vacuum4 #ie4 ,galileo's ,exp]im5t4--,! fact t bodies ( diff]5t weight t5d to fall at ! same rate 0 fir/ exp]im5tally %[n by ,galileo by dropp+ a #a-lb4 & a #ajj-lb4 ball f ! top ( ! lean+ t[] ( ,pisa 9 ,italy 7repres5t$ 9 ,fig4 #gi74 ,bo? />t+ at ! same "t /ruck ! gr\nd toge!r4 ,galileo inf]r$ f ?is t fea!rs & o!r light objects w\ld fall at ! same rate z iron or lead 7 x n = ! resi/ance ( ! air4 ,aft] ! inv5tion ( ! air pump ?is supposition 0 v]ifi$ z j expla9$4 ,illu/ration3 ,,fig4 #gi4--,lean+ t[] ( ,pisa4 #if4 ,accel]ation ,due to ,gravity4--,if a body falls freely1 t is )\t meet+ a resi/ance or a ret>d+ influ5ce1 its motion w cont9ually increase4 ,! increase 9 motion is f\nd to be con/ant or uni=m dur+ ea* second4 ,?is uni=m increase 9 motion or 9 velocity ( a fall+ body gives "o ( ! be/ illu/rations t we h ( uni=mly accel]at$ motion4 7,art4 #ge47 ,on ! o!r h&1 a body ?r[n upw>d has uni=mly ret>d$ motion1 t is1 its accel]ation is d[nw>d4 ,! velocity acquir$ by a fall+ body 9 unit "t is call$ its accel]ation1 or ! accel]ation due to gravity1 & is equal to #cb4af ft4 7#ihj cm47 p] second1 d[nw>d1 ea* second ( "t4 ,9 "o second1 !re=e1 a fall+ body ga9s a velocity ( #cb4af ft4 7#ihj cm47 p] second1 d[nw>d4 ,9 two seconds x ga9s twice ?is1 & s on4 ,9 =mulas1 ! accel]ation ( gravity is repres5t$ by g & ! numb] ( seconds by t1 !re=e ! =mula = f9d+ ! velocity1 ,v1,f ( a fall+ body />t+ f re/ is ,v gt4 ,9 /udy+ gravity 7,art4 #hi7 we le>n$ t its =ce v>ies z "o moves t[>d or away f ! equator4 7,h[87 ,9 latitude #ch ! accel]ation ( gravity is #ihj cm4 p] second ea* second ( "t4 ,f ,v repres5ts ! velocity ( a fall+ body at ! end ( t seconds4 #ig4 ,exp]im5tal ,/udy ( ,fall+ ,bodies4--,to /udy fall+ bodies exp]im5tally by obs]v+ ! fall ( unob/ruct$ bodies is a difficult matt]4 ,_m devices h be5 us$ to r$uce ! motion s t ! action ( a fall+ body may be obs]v$ )9 ! limits ( a laboratory or lecture room4 ,! simple/ ( ^!1 & 9 "s respects ! mo/ satisfactory1 0 us$ by ,galileo4 ,x consi/s ( an incl9$ plane :i* r$uces ! effective compon5t ( ! =ce ( gravity s t ! motion ( a body roll+ d[n ! plane may be obs]v$ = sev]al seconds4 ,= illu/rat+ ?is pr9ciple a /eel piano wire has be5 select$ z be+ ! simple/ & ! mo/ easily und]/ood4 ,?is wire is /ret*$ taut across a room by a turn-buckle s t its slope is ab\t "o 9 sixte54 7,see ,fig4 #hj47 ,d[n ?is wire a weight$ pulley is all[$ to run & ! di/ance x travels 9 #a1 #b1 #c1 & #d seconds is obs]v$4 ,f ^! obs]vations we c compute ! di/ance cov]$ ea* second & ! velocity at ! end ( ea* second4 ,illu/ration3 ,,fig4 #hj4--;,app>atus to illu/rate uni=mly accel]at$ motion4 ,9 ,fig4 #fc1 if ,,og repres5ts ! weight ( ! body or ! pull ( gravity1 !n ! l9e ,,or w repres5t ! effective compon5t along ! wire1 & ,,os ! non-effective compon5t aga9/ ! wire4 ,s9ce ! ratio ( ! height ( ! plane to its l5g? is z "o to sixte51 !n ! motion along ! wire 9 ,fig4 #hj w be "o-sixte5? t ( a fall+ body4 #ih4 ,summ>y ( ,results4--,! foll[+ table gives ! results t h be5 obta9$ ) an app>atus arrang$ z %[n above4 ,9 ?is table1 column #b is ! "o :i* conta9s ! results directly obs]v$ by ! use ( ! app>atus4 ,columns1 #c1 #d1 & #e are comput$ f prec$+ columns4 7#a7 7#b7 7#c7 7#d7 7#e7 ,no4 ( ,total ,di/ance ,velocity at ,accel]ation seconds di/ance ea* second end ( second ea* second mov$ ,p] second ,p] second #a #cj cm4 #cj cm4 #fj cm4 #fj cm4 #b #abj cm4 #ij cm4 #abj cm4 #fj cm4 #c #bgj cm4 #aej cm4 #ahj cm4 #fj cm4 #d #dhj cm4 #baj cm4 #bdj cm4 #fj cm4 ,column #e %[s t ! accel]ation is uni=m1 or ! same ea* second4 ,column #d %[s t ! velocity increases ) ! numb] ( seconds or t ,v at4 ,column #c %[s t ! increase 9 motion f #a second to ! next is j equal to ! accel]ation or #fj cm4 ,?is is repres5t$ by ! foll[+ =mula3 s #a_/b a7#bt - #a74 ,! results ( ! second column1 x may be se51 increase z #a3d3i3af1 :ile ! numb] ( seconds v>y z #a3b3c3d4 ,t is1 ! total di/ance cov]$ is proportional to ! squ>e ( ! numb] ( seconds4 ,?is fact express$ z a =mula gives3 ,s #a_/b;at4 ,sub/itut+ g1 ! symbol = ! accel]ation ( gravity1 = a 9 ! above =mulas1 we h3 7#a7 ,v gt1 7#b7 ,s #a_/b;gt1 7#c7 s #a_/b;g7#bt - #a74 #ii4 ,laws ( ,fall+ ,bodies4--,^! =mulas may be /at$ z foll[s = a body :i* falls f re/3 #a4 ,! velocity ( a freely fall+ body at ! end ( any second is equal to #cb4af ft4 p] sec4 or #ihj cm4 p] second multipli$ by ! numb] ( ! second4 #b4 ,! di/ance pass$ ?r\gh by a freely fall+ body dur+ any numb] ( seconds is equal to ! squ>e ( ! numb] ( seconds multipli$ by #af4jh ft4 or #dij cm4 #c4 ,! di/ance pass$ ?r\gh by a freely fall+ body dur+ any second is equal to #af4jh feet or #dij cm4 multipli$ by "o less ?an twice ! numb] ( ! second4 ,important ,topics #a4 ,fall+ bodies4 #b4 ,galileo's exp]im5t4 #c4 ,accel]ation due to gravity4 #d4 ,laws ( fall+ bodies4 ,ex]cises #a4 ,h[ f> does a body fall dur+ ! fir/ second8 ,acc\nt = ! fact t ?is di/ance is num]ically equal to half ! accel]ation4 #b4 7a7 ,:at is ! velocity ( a fall+ body at ! end ( ! fir/ second8 7b7 ,h[ f> does x fall dur+ ! second second8 7c7 ,acc\nt = ! diff]5ce betwe5 ^! numb]s4 #c4 ,:at is ! velocity ( a fall+ body at ! end ( ! fif? second8 #d4 ,h[ f> does a body fall 7a7 9 #e seconds 7b7 9 #f seconds 7c7 dur+ ! six? second8 #e4 7a7 ,:at is ! diff]5ce betwe5 ! av]age velocity dur+ ! six? second & ! velocity at ! beg9n+ ( t second8 7b7 ,is ?is diff]5ce equal to t f\nd 9 ! second problem8 ,:y8 #f4 ,a /one dropp$ f a cliff /rikes ! foot ( x 9 #e seconds4 ,:at is ! height ( ! cliff8 #g4 ,:y is x t ! increas$ weight ( a body :5 tak5 to high] latitudes causes x to fall fa/]1 :ile at ! same place a heavy body falls no fa/] ?an a light "o8 #h4 ,:5 a tra9 is leav+ a /ation its accel]ation gradually decreases to z]o1 al?\gh ! eng9e cont9ues to pull4 ,expla94 #i4 ,w\ld y expect ! motion ( equally smoo? & p]fect sph]es ( diff]5t weight & mat]ial to be equally accel]at$ on ! same incl9$ plane8 ,give reason = y\r answ]4 ,try ! exp]im5t4 #aj4 ,a body is ?r[n upw>d ) ! velocity ( #fd4cb ft4 p] sec4 ,h[ _m seconds w x rise8 ,h[ f> w x rise8 ,h[ _m seconds w x /ay 9 ! air be=e /rik+ ! gr\nd8 #aa4 #cb4af feet h[ _m c5timet]s8 #ab4 ,! accel]ation ( a freely fall+ body is con/ant at any "o place4 ,:at does ?is %[ ab\t ! pull :i* ! e>? ex]ts on ! body8 7#g7 ,,! ,,p5dulum #ajj4 ,! ,simple ,p5dulum4--,any body susp5d$ s z to sw+ freely to & fro is a p5dulum1 z 9 ,fig4 #ha4 ,a simple p5dulum is def9$ z a s+le p>ticle ( matt] susp5d$ by a cord )\t weight4 ,x is ( c\rse impossible to con/ruct su* a p5dulum4 ,a small metal ball susp5d$ by a ?read is approximately a simple p5dulum4 ,:5 all[$ to sw+ its vibrations are made 9 equal times4 ,?is feature ( ! motion ( a p5dulum 0 fir/ notic$ by ,galileo :ile wat*+ ! sl[ oscillations ( a bronze *&eli] susp5d$ 9 ! ,ca!dral 9 ,pisa4 ,illu/ration3 ,,fig4 #ha--;,a simple p5dulum4 #aja4 ,def9ition ( ,t]ms4 ,! c5t] ( susp5sion is ! po9t ab\t :i* ! p5dulum sw+s4 ,a s+le vibration is "o sw+ across ! arc4 ,a complete or d\ble vibration is ! sw+ across ! arc & back aga94 ,! "t requir$ = a d\ble vibration is call$ ! p]iod4 ,! l5g? ( a simple p5dulum is approximately ! di/ance f ! po9t ( support to ! c5t] ( ! bob4 ,a seconds p5dulum is "o mak+ a s+le vibration p] second4 ,its l5g? at sea-level1 at ,new ,york is #ii4ca cm4 or #ci4a 941 at ! equator #ci4ja 941 at ! poles #ci4bb 94 ,a comp\nd p5dulum is "o hav+ an appreciable portion ( its mass else:]e ?an 9 ! small compact body or sph]e call$ a bob4 ,! ord9>y clock p5dulum or a met] /ick susp5d$ by "o end are examples ( comp\nd p5dulums4 ,! amplitude ( a vibration is "o-half ! arc ?r\gh :i* x sw+s1 = example1 ! arc ,,dc or ! angle ,,dac 9 ,fig4 #ha4 #ajb4 ,laws ( ! ,p5dulum4--,! foll[+ laws may be /at$3 #a4 ,! p]iod ( a p5dulum is n affect$ by its mass or ! mat]ial ( :i* ! p5dulum is made4 #b4 ,= small amplitudes1 ! p]iod is n affect$ by ! l5g? ( ! arc ?r\gh :i* x sw+s4 #c4 ,! p]iod is directly proportional to ! squ>e root ( ! l5g?4 ,express$ ma!matically1 t_/t l_/l4 #ajc4 ,uses ( ! ,p5dulum4--,! *ief use ( ! p5dulum is to regulate motion 9 clocks4 ,! :eels are kept 9 motion by a spr+ or a weight & ! regulation is effect$ by an escapem5t 7,fig4 #hb74 ,at ea* vibration ( ! p5dulum "o too? ( ! :eel ,d slips pa/ ! prong at "o end ( ! escapem5t ,c1 at ! same "t giv+ a slight pu% to ! escapem5t4 ,?is pu% transmitt$ to ! p5dulum keeps x 9 motion4 ,9 ?is way1 ! motion ( ! :eel "w & ! h&s is controll$4 ,ano!r use ( ! p5dulum is 9 f9d+ ! accel]ation ( gravity1 by us+ ! =mula1 t 7l_/g71 9 :i* t is ! "t 9 seconds ( a s+le vibration & l ! l5g? ( ! p5dulum4 ,if1 = example1 ! l5g? ( ! seconds p5dulum is #ii4ca cm41 !n #a 7#ii4ca_/;g72 squ>+ bo? sides ( ! equation1 we h #a 7#ii4ca_/;g71 or g #ii4ca_/a #ihj4a cm4 p] sec41 p] sec4 ,f ?is x foll[s t1 s9ce ! =ce ( gravity dep5ds ^u ! di/ance f ! c5t] ( ! e>?1 ! p5dulum may be us$ to det]m9e ! elevation ( a place above sea level & also ! %ape ( ! e>?4 ,important ,topics #a4 ,simple p5dulum4 #b4 ,def9itions ( t]ms us$4 #c4 ,laws ( ! p5dulum4 #d4 ,uses ( ! p5dulum4 ,ex]cises #a4 ,:at is ! usual %ape ( ! bob ( a clock p5dulum8 ,:y is ?is %ape us$ in/ead ( a sph]e8 #b4 ,remov+ ! bob f a clock p5dulum has :at effect on its motion8 ,also on ! motion ( ! h&s8 #c4 ,h[ does ! expansion ( ! rod ( a p5dulum 9 summ] & its contraction 9 w9t] affect ! keep+ ( "t by a clock8 ,h[ c ?is be correct$8 #d4 ,ma/] clocks t control ! "t ( a railway sy/em h a cup ( m]cury = a bob4 ,?is automatically keeps ! same rate ( vibration ?r\gh any *anges ( temp]ature4 ,h[8 #e4 ,h[ w ! l5g? ( a seconds p5dulum at ,d5v]1 #a mile above sea-level1 comp>e ) "o at ,new ,york8 ,:y8 ,illu/ration3 ,,fig4 #hb--;,escapem5t & p5dulum ( a clock4 #f4 ,:at is ! p]iod ( a p5dulum #i 94 long8 ,note4 ,9 problems involv+ ! use ( ! ?ird law1 use ! l5g? ( a seconds p5dulum = l1 & call its p]iod #a4 #g4 ,a sw+ is #bj ft4 high1 f9d ! "t requir$ = "o sw+ across ! arc4 #h4 ,a p5dulum is #fj cm4 long4 ,:at is its p]iod8 #i4 ,if 9 a gymnasium a pupil takes #c sec4 to sw+ once across :ile hang+ f a r+1 h[ long a p5dulum is =m$8 #aj4 ,a clock p5dulum makes f\r vibrations a second1 :at is its l5g?8 ,review ,outl9e3 ,=ce & ,motion ,=ce2 def9ition1 elem5ts1 h[ measur$1 units1 dyne4 ,graphic ,repres5tation2 typical examples ( f9d+ a compon5t1 a resultant1 or an equilibrant4 ,motion2 ,laws ( motion 7#c71 in]tia1 curvil9e> motion1 c5trifugal =ce1 mom5tum1 7,m mv71 reaction1 /ress & /ra94 ,mom5t ( ,=ce2 p>allel =ces1 c\ple1 effective & non-effective compon5t4 ,gravitation2 law2 gravity1 c5t] (2 weight4 ,equilibrium #c =ms2 /ability1 h[ increas$4 ,fall+ ,bodies2 velocity1 accel]ation1 g1 ,laws2 ,v gt1 ,s 7#a_/b7;gt - s 7#a_/b7;g7#bt - #a74 ,p5dulum2 simple1 seconds1 laws 7#c71 t 7l_/g74 ,,*apt] ,,vi ,,"w ,,& ,,en]gy #ajd4 ,"w4--,:5ev] a =ce moves a body ^u :i* x acts1 x is said to d "w ^u t body4 ,= example1 if a man pu%es a :eelb>r[ along a pa?1 he is do+ "w on x z long z ! :eelb>r[ moves1 b if ! :eelb>r[ /rikes a /one & ! man cont9ues to pu% & no motion results1 f a sci5tific po9t ( view he is !n do+ no "w on x4 ,"w signifies ! ov]com+ ( resi/ance1 & unless ! resi/ance is ov]come no "w is done4 ,lift+ a weight is do+ "w on x1 support+ a weight is n1 al?\gh ! latt] may be ne>ly z tiresome z ! =m]4 ,"w z us$ 9 sci5ce is a te*nical t]m4 ,d n atta* to x mean+s :i* x has 9 e-day spee*4 #aje4 ,measurem5t ( ,"w4--,"w is measur$ by ! product ( ! =ce by ! displacem5t caus$ 9 ! direction ( ! =ce1 t is ,w fs4 ,!re=e if a unit ( =ce acts ?r\gh a unit ( space1 a unit ( "w w be done4 ,!re are naturally sev]al units ( "w dep5d+ ^u ! units ( =ce & space employ$4 ,engli% ,"w ,unit4--,if ! =ce ( "o p\nd acts ?r\gh ! di/ance ( "o foot1 a foot-p\nd ( "w is done4 ,a foot-p\nd is def9$ z ! "w done :5 #a lb4 is lift$ #a ft4 aga9/ ! =ce ( gravity4 ,metric ,"w ,unit4--,if ! =ce is "o kilogram & ! di/ance "o met]1 "o kilogram-met] ( "w is done4 ,absolute ,"w ,unit4--,if ! =ce ( "o dyne acts ?r\gh ! di/ance ( "o c5timet] a dyne-c5timet] ( "w is done4 ,?is usually is call$ an i4 ,o!r "w units are sometimes us$ dep5d+ ^u ! =ce & di/ance units employ$4 ,"o1 ! i1 is equal to #aj1jjj1jjj ergs or #aj ergs4 ,problem4--,if a load is drawn #b miles by a team ex]t+ #ejj lbs4 =ce1 h[ mu* "w is done8 ,solution4--,s9ce ! =ce employ$ is #ejj lbs41 & ! di/ance is #b #ebhj ft41 ! "w done is #ejj #b #ebhj or #e1bhj1jjj ft4-lbs4 #ajf4 ,en]gy4--,9 ! v>i\s cases sugge/$ 9 ! p>agraphs ^u "w1 an ag5t1 a man1 an animal or a ma*9e1 0 m5tion$ z putt+ =? an ef=t 9 ord] to d ! "w4 ,x is also true t 9 ord] to p]=m "w an ag5t mu/ employ en]gy1 or ! en]gy ( a body is its capacity = do+ "w4 ,:]e an ag5t does "w ^u a body1 z 9 w9d+ up a spr+ or 9 lift+ a weight1 ! body ^u :i* ! "w has be5 done may acquire en]gy by hav+ "w done ^u x4 ,t is1 x may become able to d "w itself ^u "s o!r body4 ,= in/ance1 a lift$ weight 9 fall+ back to its fir/ position may turn :eels1 or drive a po/ into ! gr\nd aga9/ resi/ance2 a coil$ spr+ may run clock "w1 /rike a bl[1 or close a door4 ,h5ce ! en]gy1 or ! capacity = do+ "w1 is (t5 acquir$ by a body because "w has fir/ be5 done ^u t body4 #ajg4 ,pot5tial ,en]gy4--,! w\nd up spr+ may d "w because "w has fir/ be5 done ^u x4 ,! lift$ weight may also d "w because "w has fir/ be5 done 9 rais+ x to its elevat$ position s9ce 9 fall+ x may gr9d an object to p[d]1 lift ano!r weight or d "s o!r k9d ( "w4 ,! en]gy t a body possesses on acc\nt ( its position or %ape & a /ress to :i* x is subject$ is call$ pot5tial en]gy4 ,! pot5tial en]gy ( a body is measur$ by ! "w done 9 lift+ x1 *ang+ its %ape1 or by br++ ab\t ! conditions by :i* x c d "w4 ,?us if a block ( iron weigh+ #bjjj lbs4 is lift$ #bj ft41 x possesses #dj1jjj ft4-lbs4 ( pot5tial en]gy4 ,x is !re=e able to d #dj1jjj ft4-lbs4 ( "w 9 fall+ back to its fir/ position4 ,if ! block j m5tion$ %\ld fall f its elevat$ position ^u a po/1 x c\ld drive ! po/ into ! gr\nd because its motion at ! in/ant ( /rik+ enables x to d "w4 ,to compute pot5tial en]gy y compute ! "w done ^u ! body4 ,t is1 ,p4,e4 w h or f s4 #ajh4 ,k9etic ,en]gy4--,! en]gy due to ! motion ( a body is call$ k9etic en]gy4 ,! am\nt ( k9etic en]gy 9 a body may be measur$ by ! am\nt ( "w done to put x 9 motion4 ,x is usually comput$1 h[ev]1 by us+ its mass & velocity on /rik+4 ,to illu/rate1 a #ajj-lb4 ball is lift$ #af ft4 ,! "w done ^u x1 & h5ce its pot5tial en]gy1 is #afjj ft4-lbs4 ,on fall+ to ! gr\nd aga91 ?is w be *ang$ into k9etic en]gy1 or !re w be #afjj ft4-lbs4 ( k9etic en]gy on /rik+4 ,x w be not$ t s9ce en]gy is measur$ by ! "w x c d1 "w units are always us$ 9 measur+ en]gy4 ,to compute ! k9etic en]gy ( a fall+ body by simply us+ its mass & velocity "o proce$s z foll[s1 9 solv+ ! above problem3 ,fir/1 f9d ! velocity ( ! fall+ body :i* has fall5 #af ft4 ,a body falls #af ft4 9 "o second4 ,9 ?is "t x ga9s a velocity ( #cb ft4 p] second4 ,n[ us+ ! =mula = k9etic en]gy ,k4,e4 wv_/7#b;g71 we h ,k4,e4 #ajj #cb #cb_/7b #cb7 #afjj ft4-lbs4 z be=e4 ,! =mula1 ,k4,e4 wv_/7#b;g71 may be d]iv$ 9 ! foll[+ mann]3 ,! k9etic en]gy ( a fall+ body equals ! "w done 9 giv+ x its motion1 t is1 ,k4,e4 w ,s1 9 :i*1 w ! weight ( ! body & ,s ! di/ance ! body mu/ fall freely 9 ord] to acquire its velocity4 ,! di/ance fall5 by a freely fall+ body1 ,s1 #a_/b;gt gt_/7#b;g7 7,art4 #ih1 p4 #aaa74 ,n[1 v gt & v gt4 ,sub/itut+ = gt1 its equal v1 we h ,s v_/7#b;g74 ,sub/itut+ ?is value ( ,s 9 ! equation ,k4,e4 w ,s1 we h ,k4,e4 wv_/7#b;g74 ,s9ce ! k9etic en]gy ( a mov+ body dep5ds ^u its mass & velocity & n ^u ! direction ( motion1 ?is =mula may be us$ to f9d ! k9etic en]gy ( any mov+ body4 ,mass & weight 9 su* problems may be consid]$ num]ically equal4 ,important ,topics #a4 ,"w def9$4 #b4 ,"w units1 foot-p\nd1 kilogram-met]1 erg4 #c4 ,en]gy def9$4 #d4 ,k9ds ( en]gy1 pot5tial & k9etic4 ,problems #a4 ,h[ mu* "w w a #abj-lb4 boy d climb+ a m\nta9 #cjjj ft4 high8 ,%\ld ! v]tical or slant height be us$8 ,:y8 #b4 ,9 a m9e #djjj kg4 ( coal are lift$ #bbc met]s3 h[ mu* "w is done ^u ! coal8 ,:at is ! k9d & am\nt ( en]gy possess$ by ! coal8 #c4 ,a pile driv] weighs #dej lbs4 ,x is lift$ #af ft4 ,h[ mu* "w has be5 done ^u x8 ,:at k9d & am\nt ( en]gy w x h aft] fall+ #af ft4 to ! pile8 #d4 ,a tra9 weigh+ #djj tons is mov+ #cj miles p] h\r4 ,compute its k9etic en]gy4 7,*ange its weight to p\nds & velocity to feet p] second47 #e4 ,:at w\ld be ! k9etic en]gy ( ! tra9 9 problem #d if x 7 go+ #fj miles p] h\r8 ,if x 7 go+ #ij miles p] h\r8 ,h[ does d\bl+ or trebl+ ! spe$ ( an object affect its k9etic en]gy8 ,h[ does x affect its mom5tum8 #f4 ,:at is ! k9etic en]gy ( a #afjj-lb4 cannon ball mov+ #bjjj ft4 p] second8 #g4 ,m5tion z _m k9ds ( me*anical "w z y c & %[ h[ ea* satisfies ! def9ition ( "w4 #h4 ,a pile driv] weigh+ #cjjj lbs4 is lift$ #aj ft4 ,h[ mu* "w is done ^u x8 #i4 ,if ! pile driv] 9 problem #h is dropp$ ^u ! head ( a pile :i* meets an av]age resi/ance ( #cj1jjj lbs41 h[ f> w "o bl[ drive x8 #aj4 ,a #dj kg4 /one is plac$ ^u ! top ( a *imney #ej met]s high4 ,compute ! "w done 9 kilogram-met]s & foot-p\nds4 7#b7 ,,p[] ,,& ,,en]gy #aji4 ,horse-p[]4--,9 comput+ "w1 no acc\nt is tak5 ( ! "t requir$ to accompli% x4 ,b s9ce ! "t ne$$ to p]=m an und]tak+ is ( mu* importance1 ! rate ( "w1 or ! p[] or activity ( an ag5t is an important factor4 ,?us if "o ma*9e c d a piece ( "w 9 "o-fif? ! "t requir$ by ano!r ma*9e1 x is said to h five times ! p[] ( ! o!r4 ,!re=e ! p[] ( a ma*9e is ! rate at :i* x c d "w4 ,james ,watt 7#agcf-ahai71 ! inv5tor ( ! /eam-eng9e1 9 express+ ! p[] ( 8 eng9e1 us$ z a unit a horse-p[]4 ,he consid]$ t a horse c\ld d #cc1jjj ft4-lbs4 ( "w a m9ute4 ,?is is equal to #eej ft4-lbs4 p] second or #gf4je kg4-m4 p] second4 ,?is is too high a value b x has be5 us$ ev] s9ce 8 "t4 ,/eam eng9es usually h _! p[] rat$ 9 horse-p[]4 ,t is1 locomotives produce f #ejj to #aejj horse-p[]4 ,"s /ation>y & m>9e eng9es develop z high z #be1jjj horse-p[]4 ,! p[] ( an av]age horse is ab\t #c_/d horse-p[] & ( a man ab\t #a_/g horse-p[] :5 work+ cont9u\sly = sev]al h\rs4 #aaj4 ,! ,watt4--,9 ! metric sy/em1 ! erg z a unit ( "w w\ld give z a unit ( p[] #a erg p] second4 ,?is am\nt is s small1 h[ev]1 t a l>g] unit is usually employ$1 ! practical unit be+ #aj1jjj1jjj ergs a second1 t is1 "o j\le p] second4 7,see ,art4 #aje47 ,?is practical unit is call$ a ,watt aft] ,james ,watt4 ,! p[] ( dynamos is usually express$ 9 kil[atts1 a kil[att repres5t+ #ajjj watts4 ,/eam-eng9es 9 mod]n practice are (t5 rat$ 9 kil[atts in/ead ( horse-p[]4 ,a horse-p[] is equival5t to #gdf watts1 or is ne>ly #c_/d ( a kil[att4 #aaa4 ,en]gy4 ,its ,transf]5ce & ,trans=mation4 ,we h consid]$ en]gy z ! capacity = do+ "w1 & not$ ! two k9ds1 pot5tial & k9etic1 & ! facility ) :i* "o may *ange into ano!r4 ,9 fact1 ! transf]5ce ( en]gy f "o body to ano!r1 & its trans=mation f "o =m to ano!r is "o ( ! mo/ common processes 9 nature4 ,take a p5dulum 9 motion1 at ! end ( a sw+1 its en]gy be+ entirely due to its elevat$ position is all pot5tial2 at ! l[e/ po9t 9 its pa? its en]gy be+ entirely due to its motion is all k9etic4 ,! *ange goes on automatically z long z ! p5dulum sw+s4 ,a motor atta*$ by a belt to a wa%+ ma*9e is />t$ runn+4 ,! en]gy ( ! motor is transf]r$ by ! belt to ! wa%] :]e x is us$ 9 rubb+ & mov+ ! clo!s4 ,! heat us$ 9 w>m+ a h\se is usually obta9$ by burn+ coal or wood4 ,coal is believ$ to be =m$ f ! rema9s ( plants t grew 9 =m] geologic times4 ,^! plants grew ?r\gh ! help ( ! radiant en]gy ( ! sun4 ,! foll[+ are trans=mations ( en]gy t h occurr$3 ,! radiant en]gy ( sunlight 0 trans=m$ into ! *emical en]gy ( ! plants4 ,?is rema9$ z *emical en]gy :ile ! plants 7 be+ conv]t$ into coal1 0 m9$1 br\ght to ! /ove or furnace & burn$4 ,! burn+ trans=m$ ! *emical en]gy into heat en]gy 9 :i* =m we use x = w>m+ rooms4 ,take ! en]gy us$ 9 runn+ a /reet c> ^: electrical en]gy comes f a wat]fall4 ,! en]gy ( ! c> itself is me*anical4 ,its motor1 h[ev]1 receives electrical en]gy & trans=ms x into me*anical4 ,?is electrical en]gy comes along a wire f a dynamo at ! wat]fall1 :]e wat]-:eels & g5]ators trans=m into electrical en]gy ! me*anical en]gy ( ! fall+ wat]4 ,! wat] obta9$ its en]gy ( position by be+ evaporat$ by ! heat ( ! radiant en]gy ( ! sun4 ,! vapor ris+ into ! air is cond5s$ into cl\ds & ra91 & fall+ on ! m\nta9 side1 has1 f its elevat$ position1 pot5tial en]gy4 ,! ord] ( trans=mation1 !re=e1 is 9 ?is case1 radiant1 heat1 me*anical1 electrical1 & me*anical4 ,c y trace ! en]gy f ! sun /ep by /ep to ! en]gy y are us+ 9 read+ ?is page8 #aab4 ,=ms ( ,en]gy4--,a /eam-eng9e atta*$ to a tra9 ( c>s employs its en]gy 9 sett+ ! c>s 9 motion1 i4e41 9 giv+ !m k9etic en]gy & 9 ov]com+ resi/ance to motion4 ,b :at is ! s\rce ( ! en]gy ( ! eng9e8 ,x is f\nd 9 ! coal :i* x c>ries 9 its t5d]4 ,b ( :at k9d8 ,surely n k9etic1 z no motion is se54 ,x is !re=e pot5tial4 ,:at is ! s\rce ( ! en]gy ( ! coal8 ,?is "q leads u back to ! "t ( ! =mation ( coal b$s1 :5 plants grew 9 ! sunlight & /or$ up ! en]gy ( ! sun's heat & light z *emical en]gy4 ,! sun's light br+s to ! e>? ! en]gy ( ! sun1 t c5tral /oreh\se ( en]gy1 :i* has suppli$ ne>ly all ! available en]gy ^u ! e>?4 ,five =ms ( en]gy are kn[n1 viz41 me*anical1 heat1 electrical1 radiant1 & *emical4 #aac4 ,en]gy ,recogniz$ by its ,effects4--,l =ce1 en]gy is invisible & we are aw>e ( ! =ms only by ! effects produc$ by x4 ,we recognize heat by w>m+1 by expansion1 by pressure4 ,we recognize light by w>m+1 by its affect+ vision4 ,we recognize electrical en]gy by its heat1 light1 motion1 or magnetic effect4 ,we recognize me*anical en]gy by ! motion t x produces4 ,we recognize *emical en]gy by kn[+ t ! s\rce ( en]gy does n belong to any ( ! =ego+4 ,a boy or girl is able to d consid]able "w4 ,!y !re=e possess en]gy4 ,9 :at =m does ! en]gy ( ! body ma9ly occur8 ,"o c det]m9e ?is = himself by apply+ que/ions to ea* =m ( en]gy 9 turn z 9 ,art4 #aad4 #aad4 ,s\rce ( ! ,en]gy ( ! ,human ,body4--,is ! en]gy ( ! human body mo/ly heat8 ,no1 s9ce we are n v w>m4 ,is x light or electrical8 ,evid5tly n s9ce we are nei!r lum9\s nor electrical4 ,is x me*anical8 ,no1 s9ce we h our en]gy ev5 :5 at re/4 ,is x *emical8 ,x mu/ be s9ce x is none ( ! o!rs4 ,*emical en]gy is conta9$ )9 ! molecule4 ,x is a =m ( pot5tial en]gy & x is believ$ to be due to ! position ( ! atoms )9 ! molecule4 ,z a tightly coil$ wat* spr+ may h mu* en]gy )9 x1 :i* is set free on all[+ ! spr+ to uncoil1 s ! *emical en]gy is releas$ on />t+ ! *emical reaction4 ,gunp[d] & dynamite are examples ( sub/ances conta9+ *emical en]gy4 ,on explod+ ^!1 heat1 light1 & motion are produc$4 ,gasol9e1 k]os5e1 & illum9at+ gas are pur*as$ because ( ! pot5tial en]gy !y conta94 ,?is en]gy is set free by burn+ or explod+ !m4 ,! s\rce ( ! en]gy ( our bodies is ( c\rse ! food we eat4 ,! en]gy conta9$ 9 ! food is also *emical4 ,vegetables obta9 _! en]gy f ! sunlight 7radiant en]gy74 ,?is is :y plants w n gr[ 9 ! d>k4 ,! available en]gy is mo/ly conta9$ 9 ! =m ( />*1 sug> & oil4 ,dige/ion is employ$ pr9cipally to dissolve ^! sub/ances s t ! blood may absorb !m & c>ry !m to ! tissues ( ! body :]e !y are ne$$4 ,! en]gy is set free by oxidation 7burn+71 ! oxyg5 ne$$ = ?is be+ suppli$ by brea?+4 ,brea?+ also removes ! c>bon dioxide1 :i* results f ! combu/ion4 ,x is = its en]gy t our food is mo/ly requir$4 #aae4 ,cons]vation ( ,en]gy4--,9 ! /udy ( matt] we le>n$ t x is inde/ructible4 ,en]gy is also believ$ to be inde/ructible4 ,?is pr9ciple /at$ concisely tea*es t despite ! innum]able *anges :i* en]gy und]goes ! am\nt 9 ! univ]se is un*angeable1 & :ile en]gy may leave ! e>? & be lo/ z f> z we are conc]n$1 t x exi/s some:]e 9 "s =m4 ,! pr9ciple :i* tea*es ?is is call$ ! ,cons]vation ( ,en]gy4 ,! =m into :i* en]gy is f9ally trans=m$ is believ$ to be heat4 ,important ,topics #a4 ,p[] def9$4 ,units4 ,horse-p[]4 ,watt4 #b4 ,transf]5ce & trans=mations ( en]gy4 #c4 ,=ms ( en]gy2 heat1 electrical1 me*anical1 radiant1 *emical4 #d4 ,effects ( ! sev]al =ms ( en]gy4 #e4 ,en]gy ( ! human body4 #f4 ,cons]vation ( en]gy4 ,ex]cises #a4 ,a boy weigh+ #aaj lbs4 ran up a /airs #aj ft4 high1 9 #d seconds4 ,h[ mu* "w 0 done8 ,:at 0 8 rate ( "w 7foot-p\nds p] second78 ,express also 9 horse-p[]4 #b4 ,a locomotive draw+ a tra9 ex]ts a draw b> pull ( #aa1jjj lbs4 ,h[ mu* "w does x d 9 mov+ #c miles8 ,:at is its rate ( "w if x moves #c miles 9 #e m9utes8 ,express 9 horse-p[]4,g ,g ,! foll[+ =mula is ( assi/ance 9 comput+ horse-p[] 9 problems3 ,h4 p4 7lbs4 ft47_/7#eej sec474 #c4 ,if #djj kg4 are lift$ #ce met]s 9 #e seconds :at "w is done8 ,:at is ! rate ( "w8 ,express 9 horse-p[]1 watts & kil[atts4 #d4 ,trace ! en]gy ( a mov+ railway tra9 back to its s\rce 9 ! sun4 #e4 ,:y does turn+ ! propell] ( a motor boat cause ! boat to move8 #f4 ,does x require m p[] to g up a flight ( /airs 9 #e seconds ?an 9 #aj seconds8 ,expla94 ,is m "w done 9 "o case ?an 9 ! o!r8 ,:y8 #g4 ,c #a man c>ry+ bricks up to a c]ta9 elevation = #abj days d z mu* "w z #abj m5 c>ry+ up bricks = #a day8 #h4 ,if ! #a man & #abj m5 ( problem #g d ! same am\nt ( "w h !y ! same p[]8 ,expla94 #i4 ,if #afj cu4 ft4 ( wat] fl[ ea* second ov] a dam #ae;ft4 high :at is ! available p[]8 #aj4 ,:at p[] mu/ an eng9e h to fill a tank #aa #h #e ft4 ) wat] #abj ft4 above ! supply1 9 #e m9utes8 #aa4 ,a hod c>ri] weigh+ #aej lbs4 c>ries a load ( bricks weigh+ #ajj lbs4 up a ladd] #cj ft4 high4 ,h[ mu* "w does he d8 #ab4 ,h[ mu* "w c a #d-;horse-p[] eng9e d 9 #e m9utes8 #ac4 ,f9d ! horse-p[] ( a w9dmill t pumps #f tons ( wat] f a well #ij ft4 deep 9 #cj m9utes4 #ad4 ,h[ _m horse-p[] are !re 9 a wat]fall #bj ft4 high ov] :i* #ejj cu4 ft4 ( wat] pass 9 a m9ute8 #ae4 ,! ,*icago dra9age canal has a fl[ ( ab\t #fjjj cu4 ft4 a second4 ,if at ! controll+ works !re is an available fall ( #cd ft4 h[ _m horse-p[] c be develop$8 #af4 ,h[ long w x take a #aj-;horse-p[] pump to fill a tank ( #djjj gallons capacity1 /&+ #cjj ft4 above ! pump8 #ag4 ,a boy weigh+ #afb lbs4 climbs a /airway a v]tical height ( #ad ft4 9 #ad4f seconds4 ,h[ mu* p[] does he ex]t8 #ah4 ,! same boy does ! same "w a second "t 9 #d4b seconds4 ,h[ mu* p[] does he ex]t ?is "t8 ,:at causes ! diff]5ce8 #ai4 ,:at is a horse-p[]-h\r8 a kil[att-h\r8 7#c7 ,,simple ,,ma*9es ,,& ,,! ,,lev] #aaf4 ,ma*9es & ,_! ,uses4--,a man1 :ile /&+ on ! gr\nd1 c draw a flag to ! top ( a pole1 by us+ a rope pass+ ov] a pulley4 ,a boy c unscrew a tightly fitt+ nut t he _c move ) 8 f+]s1 by us+ a wr5*4 ,a woman c sew a long seam by us+ a sew+ ma*9e 9 mu* less "t ?an by h&4 ,a girl c button h] %oes mu* quick] & easi] ) a button-hook ?an ) h] f+]s4 ,^! illu/rations %[ "s ( ! reasons :y ma*9es are us$4 ,9 fact x is almo/ impossible to d any k9d ( "w effici5tly )\t us+ "o or m ma*9es4 #aag4 ,advantages ( ,ma*9es4--7a7 ,_m ma*9es make possible an increas$ spe$ z 9 a sew+ ma*9e or a bicycle4 7b7 ,o!r ma*9es ex]t an increas$ =ce4 ,a rope & a set ( pulleys may enable a man to lift a heavy object su* z a safe or a piano4 ,by ! use ( a b> a man c m easily move a l>ge rock4 7,see ,fig4 #hc47 ,illu/ration3 ,,fig4 #hc4--,! rock is easily mov$4 7c7 ,! direction ( a =ce may be *ang$ ?us enabl+ "w to be done t c\ld n be readily accompli%$ o!rwise4 ,z1 e4g41 ! use ( a pulley 9 rais+ a flag to ! top ( a flag pole1 or 9 rais+ a bucket ( ore f a m9e by us+ a horse atta*$ to a rope pass+ ov] two or m pulleys4 7,see ,fig4 #hd47 7d7 ,o!r ag5ts ?an man or animals c be us$ su* z electricity1 wat] p[]1 ! w9d1 /eam1 etc4 ,fig4 #he repres5ts a w9dmill (t5 us$ 9 pump+ wat]4 ,a ma*9e is a device = transf]r+ or trans=m+ en]gy4 ,x is usually !re=e an in/rum5t = do+ "w4 ,an electric motor is a ma*9e s9ce x trans=ms ! en]gy ( ! electric curr5t into motion or me*anical en]gy1 & transf]s ! en]gy f ! wire to ! driv+ pulley4 ,illu/ration3 ,,fig4 #hd4--,! horse lifts ! bucket ( ore4 #aah4 ,a ,ma*9e ,_c ,create ,en]gy4--,:atev] does "w ^u a ma*9e 7a man1 mov+ wat]1 w9d1 etc47 loses en]gy :i* is employ$ 9 do+ ! "w ( ! ma*9e4 ,a pair ( %e>s is a ma*9e s9ce x transf]s en]gy f ! h& to ! edges t d ! cutt+4 ,our own bodies are (t5 consid]$ z ma*9es s9ce !y bo? transf] & trans=m en]gy4 ,we mu/ keep 9 m9d t a ma*9e _c create en]gy4 ,! pr9ciple ( ,cons]vation ( ,en]gy is j z explicit on "o side z ! o!r4 ,j z en]gy1 _c be de/roy$1 s en]gy _c be creat$4 ,a ma*9e c give out no m en]gy ?an is giv5 to x4 ,x acts simply z an ag5t 9 transf]r+ en]gy f "o body to ano!r4 ,_m ef=ts h be5 made to con/ruct ma*9es t :5 once />t$ w run !mselves1 giv+ out m en]gy ?an !y receive4 ,su* ef=ts1 call$ seek+ = p]petual motion1 h nev] succe$$4 ,?is fact is /rong evid5ce 9 favor ( ! pr9ciple ( ! cons]vation ( en]gy4 ,illu/ration3 ,,fig4 #he4--;,a w9dmill4 #aai4 ,law ( ,ma*9es4--,:5 a body receives en]gy1 "w is done ^u x4 ,!re=e "w is done ^u a ma*9e :5 x receives en]gy & ! ma*9e does "w ^u ! body to :i* x gives ! en]gy4 ,9 ! op]ation ( a ma*9e1 !re=e1 two quantities ( "w are to be consid]$ & by ! pr9ciple ( ! cons]vation ( en]gy1 ^! two mu/ be equal4 ,! "w done by a ma*9e equals ! "w done ^u x1 or ! en]gy giv5 out by a ma*9e equals ! en]gy receiv$ by x4 ,^! two quantities ( "w mu/ ea* be compos$ ( a =ce factor & a space factor4 ,!re=e two =ces & two spaces are to be consid]$ 9 ! op]ation ( a ma*9e4 ,! =ce factor ( ! "w done on ! ma*9e is call$ ! =ce or ef=t4 ,x is ! =ce appli$ to ! ma*9e4 ,! =ce factor ( ! "w done by a ma*9e is call$ ! weight or resi/ance4 ,x is ! =ce ex]t$ by ! ma*9e 9 ov]com+ ! resi/ance & equals ! resi/ance ov]come4 ,if f repres5ts ! =ce or ef=t1 & ,df ! space x acts ?r\gh1 & w repres5ts ! weight or resi/ance1 & ,dw ! space x acts ?r\gh1 !n ! law ( ma*9es may be express$ by an equation1 f ,df w ,dw4 ,t is1 ! ef=t times ! di/ance ! ef=t acts equals ! resi/ance times ! di/ance ! resi/ance is mov$ or ov]come4 ,:5 ! product ( two numb]s equals ! product ( two o!r numb]s ei!r pair may be made ! means & ! o!r ! extremes ( a proportion4 ,! equation giv5 above may !re=e be express$ w3 f ,df3 ,dw4 ,or ! resi/ance is to ! ef=t z ! ef=t di/ance is to ! resi/ance di/ance4 ,! law ( ma*9es may !re=e be express$ 9 sev]al ways4 ,"o %\ld keep 9 m9d1 h[ev]1 t ! same law ( ma*9es is express$ ev5 ?\gh ! =m be diff]5t4 ,:at two ways ( express+ ! law are giv58 #abj4 ,! ,simple ,ma*9es4--,!re are b six simple ma*9es4 ,all ! v>ieties ( ma*9es kn[n are simply modifications & comb9ations ( ! six simple ma*9es4 ,! six simple ma*9es are m easily rememb]$ if we sep>ate !m into two gr\ps ( ?ree ea*4 ,! fir/ or lev] gr\p consi/s ( ^? ma*9es 9 :i* a "p revolves ab\t a fix$ axis4 ,x conta9s ! lev]1 pulley & :eel & axle4 ,! second or incl9$ plane gr\p includes ^? hav+ a slop+ surface4 ,x conta9s ! incl9$ plane1 ! w$ge1 & ! screw4 #aba4 ,! ,lev]4--,! lev] is "o ( ! simple ma*9es mo/ frequ5tly us$1 be+ se5 9 scissors1 broom1 coal %ovel1 :ip1 :eelb>r[1 tongs1 etc4 ,! lev] consi/s ( a rigid b> capable ( turn+ ab\t a fix$ axis call$ ! fulcrum4 ,9 /udy+ a lev]1 "o wi%es to "k :at weight or resi/ance x c ov]come :5 a c]ta9 =ce is appli$ to x4 ,diagrams ( lev]s1 !re=e1 conta9 ! lett]s w & f4 ,9 addition to ^!1 ,o /&s = ! fulcrum on :i* x turns4 ,by ref]r+ to ,fig4 #hf1 a1 b1 c1 "o may notice t ea* ( ^! may occupy ! middle position betwe5 ! o!r two4 ,! two =ces 7o!r ?an ! "o ex]t$ by ! fulcrum7 act+ on a lev] always oppose ea* o!r 9 ! matt] ( *ang+ rotation4 ,!y may be consid]$ z a pair ( p>allel =ces act+ on a body1 ea* t5d+ to produce rotation4 ,illu/ration3 ,,fig4 #hf4--,! ?ree classes ( lev]s4 #abb4 ,mom5t ( ,=ce4--,! effectiv5ess ( ea* =ce may !re=e be det]m9$ by comput+ its mom5t ab\t ! fix$ axis 7see ,art4 #hd71 t is1 by multiply+ ea* =ce by its di/ance to ! fulcrum or axis ( rotation4 ,let a met] /ick h a small hole bor$ ?r\gh x at ! #ej cm4 m>k ne> "o edge1 & let x be m\nt$ on a nail driv5 into a v]tical support & balanc$ by slid+ a b5t wire along x4 ,susp5d by a f9e wire or ?read a #ajj g4 weight1 #ae cm4 f ! nail & a #ej g4 weight #cj cm4 f ! nail1 on ! o!r side ( ! support4 ,^! two weights w be f\nd to balance4 ,:5 view$ f ?is side ,a 7,fig4 #hg7 t5ds to turn ! lev] 9 a clockwise direction 7d[n at "r71 ,b 9 ! c\nt]-clockwise direction 7d[n at left74 ,s9ce ! lev] balances1 ! =ces h equal & opposite effects 9 *ang+ its rotation z may also be comput$ by det]m9+ ! mom5t ( ea* =ce by multiply+ ea* by its di/ance f ! fulcrum4 ,!re=e ! effectiv5ess ( a =ce 9 *ang+ rotation dep5ds ^u ! di/ance f x to ! axis z well z ^u ! magnitude ( ! =ce4 ,illu/ration3 ,,fig4 #hg4--,! two mom5ts are equal ab\t ,c4 #ajj #ae #ej #cj4 ,f ! exp]im5t j describ$1 ! mom5t ( ! act+ =ce equals ! mom5t ( ! weight or f ,df w ,dw1 or ! ef=t times ! ef=t arm equals ! weight times ! weight arm4 ,?is equation is call$ ! law ( ! lev]4 ,x corresponds to ! g5]al law ( ma*9es & may also be writt5 w3 f ,df3 ,dw4 #abc4 ,me*anical ,advantage4--,a lev] (t5 gives an advantage because by its use "o may lift a /one or weight :i* ! unaid$ /r5g? ( man c\ld n move4 ,if ! lev] is us$ 9 lift+ a /one weigh+ #ejj lbs41 ! =ce available be+ only #ajj lbs41 !n its me*anical advantage w\ld be #e1 ! ratio ( w3f4 ,9 a simil> way1 ! me*anical advantage ( any ma*9e is f\nd by f9d+ ! ratio ( ! resi/ance or weight to ! ef=t4 ,:at mu/ be ! relative l5g?s ( ! ef=t arm & resi/ance or weight arm 9 ! example j m5tion$8 ,s9ce ! ef=t times ! ef=t arm equals ! weight times ! weight arm1 if f ,df w ,dw1 !n ,df is five times ,dw4 ,h5ce ! me*anical advantage ( a lev] is easily f\nd by f9d+ ! ratio ( ! ef=t arm to ! weight arm4 ,important ,topics #a4 ,advantage ( ma*9es4 #b4 ,ma*9es _c create en]gy4 #c4 ,law ( ma*9es4 #d4 ,six simple ma*9es4 #e4 ,lev] & pr9ciple ( mom5ts4 #f4 ,me*anical advantage ( a ma*9e4 ,ex]cises #a4 ,give six examples ( lev]s y use4 #b4 ,fig4 #hh;a repres5ts a pair ( pap] %e>s1 #hh;b a pair ( t9n]'s %e>s4 ,:i* has ! great] me*anical advantage8 ,:y8 ,expla9 :y ea* has ! mo/ effective %ape = its p>ticul> "w4 ,illu/ration3 ,,fig4 #hh4--7;a7 ,pap] %e>s4 7b7 ,t9n]'s %e>s4 #c4 ,f9d examples ( lev]s 9 a sew+ ma*9e4 #d4 ,:at w\ld result if1 9 ,art4 #abb1 ! #ajj g4 weight 7 put #be cm4 f ,o & ! #ej g4 weight #de cm4 f ,o8 ,:y8 ,expla9 us+ pr9ciple ( mom5ts4 #e4 ,h[ is ! lev] pr9ciple appli$ 9 r[+ a boat8 #f4 ,:5 y cut c>dbo>d ) %e>s1 :y d y op5 !m wide & cut ne> ! pivot8 #g4 ,9 c>ry+ a load on a /ick ov] ! %\ld] %\ld ! pack be c>ri$ ne> ! %\ld] or out on ! /ick8 ,:y8 #h4 ,h[ c two boys on a see-saw />t x )\t t\*+ ! gr\nd8 #i4 ,9 lift+ a %ovel full ( s& d y lift up ) "o h& z h>d z y pu% d[n ) ! o!r8 ,:y8 ,illu/ration3 ,,fig4 #hi4--,! hamm] is a b5t lev]4 ,:at is its me*anical advantage8 #aj4 ,:y mu/ ! h+es ( a gate #c ft4 high & #af ft4 wide be /rong] ?an ! h+es ( a gate #af ft4 high & #c ft4 wide8 #aa4 ,:5 "o sweeps ) a broom d ! h&s d equal am\nts ( "w8 ,expla94 #ab4 ,a b> #f ft4 long is us$ z a lev] to lift a weight ( #ejj lbs4 ,if ! fulcrum is plac$ #f 94 f ! weight1 :at w be ! ef=t requir$8 ,note3 two arrangem5ts ( weight1 fulcrum & ef=t are possible4 #ac4 ,! h&le ( a hamm] is #ab 94 long & ! claw t is us$ 9 draw+ a nail is #b4e 94 long4 7,see ,fig4 #hi47 ,a =ce ( #be lbs4 is requir$ to draw ! nail4 ,:at is ! resi/ance ( ! nail8 #ad4 ,! effective l5g? ( ! head ( a hamm] is #b 94 ,! h&le is #ae 94 long & ! nail holds 9 ! wood ) a =ce ( #ejj lbs4 ,only #fj lbs4 ( =ce is available at ! end ( ! h&le4 ,:at w be ! result8 #ae4 ,if an ef=t ( #ej lbs4 act+ on a ma*9e moves #aj ft41 h[ f> c x lift a weight ( #ajjj lbs48 #af4 ,a b> #aj ft4 long is to be us$ z a lev]4 ,! weight is kept #b ft4 f ! fulcrum4 ,:at diff]5t lev]s c x repres5t8 #ag4 ,! ef=t arm ( a lev] is #f ft41 ! weight arm #f 94 ,h[ long w ! lev] be8 ,give all possible answ]s4 #ah4 ,two boys c>ry a weight ( #ajj lbs4 on a pole #e ft4 long betwe5 !m4 ,:]e %\ld ! weight be plac$ 9 ord] t "o boy may c>ry "o & "o-f\r? times z mu* z ! o!r8 7#d7 ,,! ,,:eel ,,& ,,axle ,,& ,,! ,,pulley #abd4 ,! ,:eel & ,axle4--#a4 ,"o ( ! simple ma*9es mo/ commonly appli$ 9 comp\nd ma*9es is ! :eel & axle4 ,x consi/s ( a :eel ,h m\nt$ on a cyl9d] ,y s fa/5$ toge!r t bo? turn on ! same axis4 ,9 ,fig4 #ij1 ropes are %[n atta*$ to ! circumf]5ces ( ! :eel & axle4 ,sometimes a h& :eel is us$ z on ! brake ( a freight or /reet c>1 or simply a crank & h&le is us$1 z 9 ,fig4 #ia4 ,! cap/an is us$ 9 mov+ build+s4 ,sometimes two or ?ree :eels & axles are ge>$ toge!r z on a d]rick or crane z 9 ,fig4 #ib4 ,illu/ration3 ,,fig4 #ij4--,! :eel & axle4 ,illu/ration3 ,,fig4 #ia4--,w9dlass us$ 9 draw+ wat] f a well4 ,illu/ration3 ,,fig4 #ib4--;,a portable crane4 ,illu/ration3 ,,fig4 #ic4--,! :eel & axle consid]$ z a lev]4 ,illu/ration3 ,,fig4 #id4--,view ( transmission ge>s 9 an automobile4 #a1 ,drive ge>2 #b1 ,high & int]m$iate ge>2 #c1 ,l[ & rev]se ge>2 #d1 #h1 ,rev]se idl] ge>s2 #e1 #f1 #g1 ,c\nt]%aft ge>s4 7,c\rtesy ( ! ,automobile ,j\rnal47 ,illu/ration3 ,,fig4 #ie4--,r$uc+ ge> ( a /eam turb9e4 ,fig4 #ic is a diagram %[+ t ! :eel & axle acts l a lev]4 ,! axis ,d is ! fulcrum1 ! ef=t is appli$ at ,f1 at ! extremity ( a radius ( ! :eel & ! resi/+ weight ,w at ! extremity ( a radius ( ! axle4 ,h5ce1 if ,df1 ! ef=t di/ance1 is ?ree times ,dw1 ! weight di/ance1 ! weight t c be support$ is ?ree times ! ef=t4 ,"h z 9 ! lev]1 f ,df w ,dw1 or w3f ,df3,dw1 or ! ratio ( ! weight to ! ef=t equals ! ratio ( ! radius ( ! :eel to ! radius ( ! axle4 ,?is is !re=e ! me*anical advantage ( ! :eel & axle4 ,s9ce ! diamet]s or circumf]5ces are 9 ! same ratio z ! radii ^! c be us$ in/ead ( ! radii4 ,sometimes1 :5 increas$ spe$ in/ead ( increas$ =ce is desir$1 ! radius ( ! :eel or "p to :i* p[] is appli$ is less ?an t ( ! axle4 ,?is is se5 9 ! bicycle1 buzzsaw1 & bl[]4 ,sometimes ge>$ :eels us+ ! pr9ciple ( ! :eel & axle are us$ to r$uce spe$1 z 9 ! transmission ( an automobile 7see ,fig4 #id71 or ! r$uc+ ge> ( a /eam turb9e4 7,see ,figs4 #ie & #bic47 ,a bevel ge> is frequ5tly us$ to *ange ! direction ( ! =ce4 7,see ,fig4 #id47 ,illu/ration3 ,,fig4 #if4--;,a s+le movable pulley4 ,illu/ration3 ,,fig4 #ig4--;,block & tackle4 ,illu/ration3 ,,fig4 #ih4--,! fix$ pulley consid]$ z a lev]4 ,illu/ration3 ,,fig4 #ii4--,! movable pulley consid]$ z a lev]4 #abe4 ,! ,pulley4--,! pulley consi/s ( a :eel turn+ on an axis 9 a frame4 ,! :eel is call$ a %eave & ! frame a block4 ,! rim may be smoo? or groov$4 ,! groov$ rim is us$ to hold a cord or rope4 ,"o use ( ! pulley is to *ange ! direction ( ! act+ =ce z 9 ,fig4 #hd1 :]e pulley ,b *anges a horizontal pull at ,h to a d[nw>d =ce & pulley ,a *anges ?is into an upw>d =ce lift+ ! weight ,w4 ,^! pulleys are fix$ & simply *ange ! direction4 ,)\t consid]+ ! loss by friction1 ! pull at ,w w equal t at ,f4 ,sometimes1 a pulley is atta*$ to ! weight & is lift$ ) x4 ,x is !n call$ a movable pulley4 ,9 ,fig4 #if ! movable pulley is at ,p1 a fix$ pulley is at ,f4 ,:5 fix$ pulleys are us$1 a s+le cord runs ?r\gh f ! weight to ! ef=t1 s t if a =ce ( #ajj lbs4 is appli$ by ! ef=t ! same =ce is receiv$ at ! weight4 ,b ) movable pulleys sev]al sections ( cord may ext5d upw>d f ! weight ea* ) ! =ce ( ! ef=t ^u x4 ,by ?is arrangem5t1 a weight sev]al times l>g] ?an ! ef=t c be lift$4 ,fig4 #ig repres5ts :at is call$ a block & tackle4 ,if a =ce ( #ej lbs4 is ex]t$ at ,f1 ea* section ( ! rope w h ! same t5sion & h5ce ! six sections ( ! rope w support #cjj lbs4 weight4 ,! me*anical advantage ( ! pulley or ! ratio ( ! weight to ! ef=t1 !re=e1 equals ! numb] ( sections ( cord support+ ! weight4 ,! fix$ pulley repres5ts a lev]1 see ,fig4 #ih1 :]e ! ef=t & weight are equal4 ,9 ! movable pulley1 ! fulcrum 7see ,fig4 #ii7 is at ,d2 ! weight1 ,w1 is appli$ at ! c5t] ( ! pulley & ! ef=t at ,f4 ,! weight di/ance1 ,dw1 is ! radius1 & ! ef=t di/ance1 ,df1 is ! diamet] ( ! pulley4 ,s9ce ,w_/,f ,df _/ ,dw #b 9 a movable pulley1 ! weight is twice ! ef=t1 or its me*anical advantage is #b4 ,important ,topics #a4 ,:eel & ,axle1 ,law ( ,:eel & ,axle4 #b4 ,pulley1 ,fix$ & ,movable1 ,block & ,tackle1 ,law ( ,pulley4 ,ex]cises #a4 ,:y d door knobs make x easi] to unlat* doors8 ,:at simple ma*9e d !y repres5t8 ,expla94 #b4 ,:at comb9ation ( pulleys w enable a #afj-lb4 man to raise a #ijj-lb4 piano8 #c4 ,:5 y pull a nail ) an ord9>y claw hamm]1 :at is ! ef=t arm8 ! resi/ance arm8 #d4 ,h[ mu* "w is done by ! ma*9e 9 problem #b 9 lift+ ! piano #bj ft48 ,h[ mu* "w mu/ be done ^u ! ma*9e to d ?is "w8 #e4 ,! pilot :eel ( a boat has a diamet] ( #fj 942 ! diamet] ( ! axle is #f 94 ,if ! resi/ance is #age lbs41 :at =ce mu/ be appli$ to ! :eel8 #f4 ,f\r m5 raise an an*or weigh+ #a #a_/b tons1 ) a cap/an 7see ,fig4 #aaj7 hav+ a b>rel #i 94 9 diamet]4 ,! circle describ$ by ! h&-spikes is #ac #a_/b ft4 9 diamet]4 ,h[ mu* =ce mu/ ea* man ex]t8 ,illu/ration3 ,,fig4 #ajj4--,! ,cap/an4 #g4 ,a bicycle has a #bh-;94 :eel4 ,! re> sprocket is #c 94 9 diamet]1,h ! radius ( ! p$al crank is #g 942 #bd lbs4 appli$ to ! p$al gives :at =ce on ! rim ( ! :eel8 ,:at w be ! spe$ ( ! rim :5 ! p$al makes "o revolution a second8 ,h ,consid] ! diamet] ( ! front sprocket z #f in*es4 #h4 ,measure ! diamet]s ( ! l>ge & small pulleys on ! sew+-ma*9e at y\r home4 ,:at me*anical advantage 9 numb] ( revolutions does x give8 ,v]ify y\r computation by turn+ ! :eel & c\nt+ ! revolutions4 #i4 ,:at =ce is requir$ ) a s+le fix$ pulley to raise a weight ( #bjj lbs48 ,h[ f> w ! ef=t move 9 rais+ ! weight #aj ft48 ,:at is ! me*anical advantage8 #aj4 ,9 ! above problem sub/itute a s+le movable pulley = ! fix$ pulley & answ] ! same que/ions4 #aa4 ,:at is ! smalle/ numb] ( pulleys requir$ to lift a weight ( #fjj lbs4 ) a =ce ( #abj lbs48 ,h[ %\ld !y be arrang$8 #ab4 ,a d]rick 9 lift+ a safe weigh+ #b tons uses a sy/em ( pulleys employ+ #c sections ( rope4 ,:at is ! =ce requir$8 #ac4 ,"n ?ree in/ances :]e pulleys are us$ to d "w t o!rwise w\ld be difficult to d4 #ad4 ,draw a diagram = a set ( pulleys by means ( :i* #ajj lbs4 c lift #djj lbs4 7#e7 ,,! ,,incl9$ ,,plane4 ,,effici5cy #abf4 ,effici5cy4--,! g5]al law ( ma*9es :i* /ates t ! "w done by a ma*9e equals ! "w put into x requires a modification1 :5 we apply ! law 9 a practical way1 = ! reason t 9 us+ any ma*9e !re is develop$ m or less friction due to p>ts ( ! ma*9e rubb+ on ea* o!r & to ! resi/ance ( ! air z ! p>ts move ?r\gh x4 ,h5ce ! /atem5t ( ! law t accords ) actual work+ conditions runs some:at z foll[s3 ,! "w put into a ma*9e equals ! useful "w done by ! ma*9e plus ! wa/$ "w done by x4 ,! effici5cy ( a ma*9e is ! ratio ( ! useful "w done by x to ! total "w done on ! ma*9e4 ,if !re 7 no friction or wa/$ "w1 ! effici5cy w\ld be p]fect1 or1 z x is usually express$1 w\ld be #ajj p] c5t4 ,consid] a sy/em ( pulleys into :i* are put #fjj ft4-lbs4 ( "w4 ,) #dej ft4-lbs4 ( useful "w result+1 ! effici5cy w\ld be #dej #fjj #c_/d1 or #ge p] c5t4 ,9 ?is case #be p] c5t4 ( ! "w done on ! ma*9e is wa/$4 ,9 a simple lev] ! friction is slight s t ne>ly #ajj p] c5t4 effici5cy is (t5 secur$4 ,"s =ms ( ! :eel & axle h high effici5cies z 9 bicycles ) ge> :eels4 ,o!r =ms 9 :i* ropes are employ$ h m friction4 ,pulleys h sometimes effici5cies z l[ z #dj p] c5t4 :5 heavy ropes are us$4 #abg4 ,incl9$ ,plane4--,we n[ come to a type ( simple ma*9e ( l[] effici5cy ?an ^? previ\sly m5tion$4 ,^! belong to ! incl9$ plane gr\p1 :i* includes ! incl9$ plane 7see ,fig4 #aja71 ! w$ge & ! screw4 ,!y are ext5sively us$1 h[ev]1 not)/&+ _! l[ effici5cy1 on acc\nt ( (t5 giv+ a high me*anical advantage4 ,! relation betwe5 ^! ma*9es may be easily %[n1 z ! w$ge is obvi\sly a d\ble incl9$ plane4 ,9 ,art4 #hb x is %[n t ! ef=t requir$ to hold a weight ^u an incl9$ plane is to ! weight support$ z ! height ( ! plane is to its l5g?4 ,illu/ration3 ,,fig4 #aja4--;,an incl9$ plane4 ,or :ile ! weight is be+ lift$ ! v]tical height ,,bc1 ! ef=t has to move ! l5g? ( ! plane ,,ac4 ,s9ce by ! law ( ma*9es ! ef=t times its di/ance equals ! weight times its di/ance1 or ! weight is to ! ef=t z ! ef=t di/ance is to ! weight di/ance1 !re=e ! me*anical advantage ( ! incl9$ plane is ! ratio ( ! l5g? to ! height ( ! incl9$ plane4 ,incl9$ planes are us$ to raise heavy objects %ort di/ances1 z b>rels into a wagon1 & iron safes into a build+4 ,/airways are incl9$ planes ) /eps cut into !m4 #abh4 ,! ,w$ge4--,w$ges are us$ to sep>ate objects1 z 9 splitt+ wood 7see ,fig4 #ajb71 cutt+ wood1 & :]e great =ce is to be ex]t$ = %ort di/ances4 ,an axe is a w$ge1 s is a knife4 ,a =k consi/s ( sev]al r\nd w$ges set 9 a h&le4 ,! edge ( any cutt+ tool is ei!r an incl9$ plane or a w$ge4 ,our front tee? are w$ges4 ,num]\s examples ( incl9$ planes may be se5 ab\t u4 ,no def9ite /atem5t z to ! me*anical advantage ( ! w$ge c be giv5 z ! "w done dep5ds l>gely on friction4 ,! =ce us$ is g5]ally appli$ by bl[s on ! ?ick end4 ,9 g5]al1 ! long] ! w$ge = a giv5 ?ickness ! great] ! me*anical advantage4 ,illu/ration3 ,,fig4 #ajb4--,"o use ( ! w$ge4 #abi4 ,! ,screw4--,! screw is a cyl9d] ar\nd ^: circumf]5ce w9ds a spiral groove4 7,see ,fig4 #ajc47 ,! rais$ "p betwe5 ! two adjac5t grooves is ! ?read ( ! screw4 ,! screw turns 9 a block call$ a nut1 )9 :i* is a spiral groove & ?read exactly correspond+ to ^? ( ! screw4 ,! di/ance betwe5 two consecutive ?reads measur$ p>allel to ! axis is call$ ! pit* ( ! screw4 7,see ,fig4 #ajd47 ,if ! ?read w9ds ar\nd ! cyl9d] t5 times 9 ! space ( #a 941 ! screw is said to h t5 ?reads to ! in*1 ! pit* be+ #a_/aj 94 ,! screw usually is turn$ by a lev] or :eel ) ! ef=t appli$ at ! end ( ! lev]1 or at ! circumf]5ce ( ! :eel4 ,:ile ! ef=t moves once ab\t ! circumf]5ce ( ! :eel ! weight is pu%$ =w>d a di/ance equal to ! di/ance betwe5 two ?reads 7! pit* ( ! screw74 ,! "w done by ! ef=t !re=e equals ,f #br1 r be+ ! radius ( ! :eel1 & ! "w done on ! weight equals ,w s1 s be+ ! pit* ( ! screw4 ,by ! law ( ma*9es ,f #br ,w s or ,w _/ ,f 7#br7 _/ s4 ,!re=e ! me*anical advantage ( ! screw equals 7#br7 _/ s4 ,s9ce ! di/ance ! weight moves is small comp>$ to t ! p[] travels1 !re is a great ga9 9 =ce4 ,! screw is usually employ$ :]e great =ce is to be ex]t$ ?r\gh small di/ances z 9 ! vise 7,fig4 #aje7 ! jack screw 7,fig4 #ajf71 screw clamps1 to accurately measure small di/ances z 9 ! micromet] 7,fig4 #ajg7 & sph]omet]1 & to less5 ! motion 9 spe$-r$uc+ devices4 ,! worm ge> 7,fig4 #ajh7 is a modification ( ! screw t is sometimes us$ :]e a consid]able am\nt ( spe$ r$uction is requir$4 ,illu/ration3 ,,fig4 #ajc4--,! screw is a spiral incl9$ plane4 ,illu/ration3 ,,fig4 #ajd4--,! pit* is ,s4 ,illu/ration3 ,,fig4 #aje4--;,a vise4 ,illu/ration3 ,,fig4 #ajf4--;,a jack screw4 ,illu/ration3 ,,fig4 #ajg4--;,a micromet] screw4 ,illu/ration3 ,,fig4 #ajh4--,?is l>ge worm-:eel is a "p ( ! hoi/+ me*anism employ$ = ! lock gates ( ! ,sault ,/e4 ,m>ie ,canal4 ,important ,topics #a4 ,effici5cy ( ma*9es4 #b4 ,! incl9$ plane1 w$ge & screw4 ,applications4 ,ex]cises #a4 ,a plank #ab ft4 long is us$ to roll a b>rel weigh+ #bjj lbs4 into a wagon #c ft4 high4 ,f9d ! =ce requir$ p>allel to ! incl9e4 #b4 ,h[ long a plank w be ne$$ to roll an iron safe weigh+ #a-a_/b tons into a wagon #c ft4 high us+ a pull ( #fjj lbs4 p>allel to ! incl9e4 #c4 ,an ef=t ( #ej lbs4 act+ p>allel to ! plane prev5ts a #bjj-lb4 b>rel f roll+ d[n an incl9$ plane4 ,:at is ! ratio ( ! l5g? to ! height ( ! plane8 #d4 ,a man c pu% ) a =ce ( #aej lbs4 & wi%es to raise a box weigh+ #abjj lbs4 into a c>t #c ft4 high4 ,h[ long a plank mu/ he use8 #e4 ,! radius ( ! :eel ( a lett] press is #f 941 ! pit* ( its screw is #a_/d 94 ,:at pressure is produc$ by a =ce ( #dj lbs48 #f4 ,! pit* ( a screw ( a vice is #a_/d 941 ! h&le is #a ft4 long4 :at pressure c be expect$ if ! =ce us$ is #ajj lbs48 #g4 ,a jackscrew is us$ to raise a weight ( #b tons4 ,! b> ( ! jackscrew ext5ds #b ft4 f ! c5t] ( ! screw4 ,!re are two ?reads to ! in*4 ,f9d ! =ce requir$4 7#f7 ,,friction1 ,,its ,,uses ,,& ,,laws #acj4 ,friction4--,al?\gh (t5 inconv5i5t & exp5sive1 requir+ p]si/5t & elaborate ef=ts to r$uce x to a m9imum1 friction has its uses1 & advantages4 ,7 x n = friction betwe5 our %oes & ! floor or sidewalk1 we c\ld n keep our foot+4 ,friction is ! resi/ance t mu/ be ov]come :5 "o body moves ov] ano!r4 ,x is ( two k9ds1 slid+ & roll+4 ,if "o draws a block & !n a c> ( equal weight along a bo>d1 ! =ce employ$ 9 ea* case be+ measur$ by a spr+ balance1 a l>ge diff]5ce 9 ! =ce requir$ w be notic$1 %[+ h[ mu* less roll+ friction is ?an slid+ friction4 #aca4 ,ways ( ,r$uc+ ,friction4--7a7 ,friction is (t5 caus$ by ! m9ute projections ( "o surface s9k+ into ! depressions ( ! o!r surface z "o moves ov] ! o!r4 ,x foll[s1 !re=e1 t if ^! projections c\ld be made z small z possible t friction w\ld be less5$4 ,consequ5tly poli%+ is "o ( ! be/ means = r$uc+ friction4 ,9 ma*9es all mov+ surfaces are made z smoo? z possible4 ,9 diff]5t k9ds ( mat]ials ^! little ridges & depressions are diff]5tly arrang$4 7b7 ,9 ,fig4 #aji ! friction betwe5 ,r & ,s w\ld be great] ?an betwe5 ,r & ,t4 ,9 ,r & ,s ! surfaces w fit clos] toge!r ?an 9 ,r & ,t4 ,! use ( diff]5t mat]ials w r$uce friction4 ,! iron axles ( c> :eels revolve 9 be>+s ( brass4 ,jewels are us$ 9 wat*es = ! same reason4 7c7 ,ano!r v common me?od ( r$uc+ friction is by ! use ( lubricants4 ,! oil or grease us$ fills up ! irregul>ities ( ! be>+ surfaces & sep>ates !m4 ,roll+ friction is frequ5tly sub/itut$ = slid+ friction by ! use ( ball & roll] be>+s4 ,^! are us$ 9 _m ma*9es z 9 bicycles1 automobiles1 sew+ ma*9es1 etc4 7,see ,fig4 #aaj47 ,illu/ration3 ,,fig4 #aji4--,! friction betwe5 ,r & ,s is great] ?an betwe5 ,r & ,t4 #acb4 ,value ( ,friction4--,friction always h9d]s motion & :5ev] "o body moves ov] or ?r\gh ano!r ! en]gy us$ 9 ov]com+ ! friction is trans=m$ into heat :i* is tak5 up by surr\nd+ bodies & usually lo/4 ,friction is !re=e ! great ob/acle to p]fect effici5cy 9 ma*9es4 ,friction1 h[ev]1 l mo/ afflictions has its uses4 ,we w\ld f9d x h>d to get along )\t x4 ,)\t friction we c\ld nei!r walk nor run2 no ma*9es c\ld be run by belts2 railroad tra9s1 /reet c>s1 9 fact all ord9>y means ( travel w\ld be impossible1 s9ce ^! dep5d ^u friction betwe5 ! mov+ p[] & ! road = propulsion4 ,illu/ration3 ,,fig4 #aaj4--,timk5 roll] be>+s4 ,z us$ 9 ! front :eel ( an automobile4 #acc4 ,coeffici5t ( ,friction4--,! ratio betwe5 ! friction :5 motion is j />t+ & ! =ce pu%+ ! surfaces toge!r is call$ ! coeffici5t ( friction4 ,if ! block 9 ,fig4 #aaa is drawn along ! bo>d ) uni=m motion1 ! read+ ( ! spr+ balances indicates ! am\nt ( friction4 ,suppose ! friction is f\nd to be #ejj g41 & ! weight ( ! block to be #bjjj g4 ,!n ! coeffici5t ( friction = ^! two sub/ances w be #ejj_/bjjj #a_/d1 or #be p] c5t4 #acd4 ,laws ( ,friction1 ,law ,i4--,! friction :5 motion is occurr+ betwe5 two surfaces is proportional to ! =ce hold+ !m toge!r4 ,?us if "o measures ! friction :5 a brick is drawn along a bo>d1 he w f9d t x is d\bl$ if a second brick is plac$ on ! fir/4 ,on brakes great] pressure causes great] friction4 ,if a rope is drawn ?r\gh ! h&s m pressure makes m friction4 ,illu/ration3 ,,fig4 #aaa4--;,a me?od = te/+ ! friction betwe5 surfaces4 ,law ,,ii4--,friction is indep5d5t ( ! ext5t ( surface 9 contact4 ,?us a brick has ! same friction drawn on its side z on its edge1 s9ce1 al?\gh ! surface is increas$1 ! weight is un*ang$4 ,law ,,iii4--,friction is greate/ at />t+1 b aft] />t+ is practically ! same = all spe$s4 #ace4 ,fluid ,friction4--,:5 a solid moves ?r\gh a fluid1 z :5 a %ip moves ?r\gh ! wat] or railroad tra9s ?r\gh ! air1 ! resi/ance enc\nt]$ is n ! same z ) solids b increases ) ! squ>e ( ! velocity = sl[ spe$s & = high spe$s at a high] rate4 ,?is is ! reason :y x co/s s mu* to increase ! spe$ ( a fa/ tra91 s9ce ! resi/ance ( ! air becomes ! prom95t factor at high spe$s4 ,! resi/ance to ! motion ( a %ip at high spe$ is usually consid]$ to increase z ! cube ( ! velocity s t to d\ble ! spe$ ( a boat its driv+ =ce mu/ be eight times z great4 ,important ,topics #a4 ,friction3 two k9ds2 slid+ & roll+4 #b4 ,f\r ways ( r$uc+ friction4 #c4 ,uses ( friction4 #d4 ,coeffici5t ( friction4 ,?ree laws ( friction4 #e4 ,fluid friction4 ,ex]cises #a4 ,h[ long mu/ an incl9$ plane be :i* is #aj met]s high to enable a c> weigh+ #bjjj kg4 to be pu%$ up its l5g? by a =ce ( #ajj kg4 p>allel to ! incl9e8 #b4 ,/ate h[ & :]e friction is ( use 9 ! op]ation ( ! incl9$ plane1 ! w$ge1 ! screw1 ! :eel & axle4 #c4 ,a :eelb>r[ has h&les #f ft4 long4 ,if a load ( #cjj lbs4 is plac$ #ah 94 f ! axis ( ! :eel1 :at =ce plac$ at ! end ( ! h&les w be requir$ to lift x8 #d4 ,a jackscrew has #c ?reads to ! in*1 & ! lev] us$ to turn x is #d ft4 long4 ,if ! effici5cy ( ! screw is #fj p] c5t41 :at =ce mu/ be appli$ to raise a load ( #e tons8 #e4 ,9 problem #d h[ f> mu/ ! =ce move 9 rais+ ! weight #c 94 ,compute ! "w done ^u ! weight1 ! "w done by ! p[] & ! effici5cy ( ! ma*9e f ^! two am\nts ( "w4 #f4 ,:at simple ma*9es are repres5t$ 9 a jackknife1 a sew+-ma*9e1 a screw-driv]1 a plane1 a saw1 a table =k8 #g4 ,a labor] c>ries #aejj lbs4 ( brick to a plat=m #dj ft4 high4 ,h[ mu* useful "w does he d8 #h4 ,if he weighs #aej lbs4 & 8 hod weighs #aj lbs41 h[ mu* useless "w does he d 9 tak+ #cj trips to c>ry up ! bricks ( problem #g8 ,:at is 8 effici5cy8 #i4 ,if ! labor] hoi/s ! brick ( problem #g 9 a bucket weigh+ #ej lbs41 us+ a fix$ pulley & rope1 :at is ! useless "w done if x takes #ab trips to c>ry up ! brick8 ,:at is ! effici5cy ( ! device8 #aj4 ,! effici5cy ( a set ( pulleys is #gj p] c5t4 ,h[ mu* =ce %\ld be appli$ if act+ ?r\gh #ajj ft4 x is to raise a load ( #djj lbs4 #bj ft48 #aa4 ,! spokes ( ! pilot :eel ( a motor-boat are #a ft4 long1 ! axle ar\nd :i* ! rudd] ropes are w\nd is #c 94 9 diamet]4 ,:at ef=t mu/ be appli$ if ! t5sion 9 ! ropes is #ej lbs48 #ab4 ,:y are ! elevat$ railway /ations frequ5tly plac$ at ! top ( an incl9e1 ! tracks slop+ g5tly away 9 bo? directions8 #ac4 ,! screw ( a press has #d ?reads to ! in* & is work$ by a lev] ( su* l5g? t an ef=t ( #be lbs4 produces a =ce ( #b tons4 ,:at is ! l5g? ( ! lev]8 #ad4 ,x takes a horizontal =ce ( #aj lbs4 to draw a sl$ weigh+ #ej lbs4 along a horizontal surface4 ,:at is ! coeffici5t ( friction8 #ae4 ,! coeffici5t ( roll+ friction ( a railroad tra9 on a track is #j4jji4 ,:at pull w\ld an eng9e h to ex]t to haul a tra9 weigh+ #ajjj tons along a level track8 #af4 ,h[ heavy a cake ( ice c be dragg$ ov] a floor by a horizontal =ce ( #bj lbs41 if ! coeffici5t ( friction is #j4jf8 #ag4 ,! coeffici5t ( friction ( iron on iron is #j4b4 ,:at =ce c a swit* eng9e weigh+ #bj tons ex]t be=e slipp+8 #ah4 ,us+ a sy/em ( pulleys ) a d\ble movable block a man weigh+ #bjj lbs4 is j able to lift #fjj lbs4 ,:at is ! effici5cy ( ! sy/em8 #ai4 ,:at is ! horse-p[] ( a pump t c pump out a cell> full ( wat] #dj ft4 #bj ft4 by #aj ft4 deep1 9 #cj m9utes8 #bj4 ,h[ _m tons ( coal c a #e horse-p[] hoi/+ eng9e raise 9 #cj m9utes f a b>ge to ! coal pockets1 a height ( #ej ft48 7#g7 ,,wat] ,,p[] #acf4 ,en]gy ( ,fall+ ,wat]4--,! en]gy ( fall+ & runn+ wat] has be5 us$ f ! e>lie/ times = develop+ p[] & runn+ ma*9]y4 ,! en]gy is d]iv$ f ! action ( ! mov+ wat] 9 /rik+ & turn+ "s =m ( wat]-:eel1 sev]al v>ieties ( :i* are describ$ bel[4 ,! ,ov]%ot ,:eel4--,! ov]%ot :eel 7,fig4 #aab7 is turn$ by ! weight ( ! wat] 9 ! buckets4 ,x 0 =m]ly mu* us$ 9 ! hilly & m\nta9\s sections ( ?is c\ntry = runn+ sawmills & gri/ mills z x is v easily made & requires only a small am\nt ( wat]4 ,its effici5cy is high1 be+ f #hj to #ij p] c5t41 ! loss be+ due to friction & spill+ ( wat] f ! buckets4 ,to secure ?is high effici5cy ! ov]%ot :eel mu/ h a diamet] equal to ! height ( ! fall :i* may be z mu* z #hj or #ij ft4 ,illu/ration3 ,,fig4 #aab4--,ov]%ot wat] :eel4 ,illu/ration3 ,,fig4 #aac4--,und]%ot wat] :eel4 ,illu/ration3 ,,fig4 #aad4--;,diagram illu/rat+ ! pr9ciple ( ! ,pelton :eel4 ,! ,und]%ot ,:eel4--,! old /yle und]%ot :eel 7,fig4 #aac7 is us$ 9 level c\ntries1 :]e !re is little fall1 (t5 to raise wat] = irrigation4 ,its effici5cy is v l[1 seldom ris+ m ?an #be p] c5t4 ,! pr9ciple ( ! und]%ot :eel1 h[ev]1 is ext5sively us$ 9 ! wat] motor & ! ,pelton :eel 7,fig4 #aad74 ,9 ^! ! wat] is deliv]$ f a nozzle 9 a jet aga9/ ! l[] buckets ( ! :eel4 ,!y h an effici5cy ( ab\t #hj p] c5t4 & are mu* us$ 9 cities = runn+ small ma*9es1 wa%+ ma*9es1 pipe organ bl[]s1 etc41 & 9 m\nta9\s di/ricts :]e ! head is great4 ,illu/ration3 ,,fig4 #aae4--;,diagram ( a hydro-electric p[] h\se %[+ a v]tical turb9e ,a ) p5/ock ,b & tail race ,c4 ,illu/ration3 ,,fig4 #aaf4--,! out] case ( a turb9e %[+ ! me*anism = controll+ ! gates4 ,illu/ration3 ,,fig4 #aag4--;,inn] case ( a turb9e %[+ ! gates & ! l[] end ( ! runn] )94 ,illu/ration3 ,,fig4 #aah4--,! runn] ( a turb9e4 ,illu/ration3 ,,fig4 #aai4--,turb9e & g5]ator ( ! ,tacoma hydro-electric p[] plant4 #acg4 ,! ,turb9e4--,! turb9e is n[ us$ m ?an any o!r =m ( wat]-:eel4 ,x 0 inv5t$ 9 #ahbg by ,de ,f\rneyron 9 ,france4 ,x c be us$ ) a small or l>ge am\nt ( wat]1 ! p[] dep5d+ on ! head 7! height ( ! wat]1 9 ! res]voir above ! :eel74 ,x is ! mo/ effici5t type ( wat]-:eel1 effici5cies ( #ij p] c5t4 (t5 be+ obta9$4 ,! :eel is entirely "u wat] 7,fig4 #aae74 ,x is enclos$ 9 an out] case 7,fig4 #aaf7 :i* is connect$ ) ! res]voir by a p5/ock or pipe & is always kept full ( wat]4 ,! :eel itself is made 9 two p>ts1 a rotat+ "p call$ ! runn] 7see ,fig4 #aah7 & an inn] case 7,fig4 #aag7 ) gates t regulate ! am\nt ( wat] ent]+ ! :eel4 ,?is case has blades curv$ s t ! wat] c /rike ! curv$ blades ( ! rotat+ "p 7,fig4 #aah7 at ! angle t is be/ adapt$ to use ! en]gy ( ! wat]4 ,! wat] !n drops ?r\gh ! c5tral op5+ into ! tail race bel[ 7see ,fig4 #aae74 ,! en]gy available is ! product ( ! weight ( ! wat] & ! head4 ,! turb9e is ext5sively us$ to furni% p[] = g5]at+ electricity at places :]e !re is a suffici5t fall ( wat]4 ,! electrical en]gy ?us develop$ is transmitt$ f #ej to #bjj miles to cities :]e x is us$ 9 runn+ /reet c>s1 electric light+1 etc4 ,turb9es c be made to revolve ab\t ei!r v]tical or horizontal axes4 ,fig4 #aai repres5ts a horizontal wat] turb9e connect$ to a dynamo4 ,comp>e ?is ) ! v]tical turb9e 9 ,fig4 #aae4 ,ex]cises #a4 ,does a p]son d m "w :5 he goes up a flight ( /airs 9 #e seconds ?an :5 he goes up 9 #ae seconds8 ,expla94 #b4 ,a motorcycle has a #d horse-p[] motor & c g at a rate ( #ej miles p] h\r4 ,:y _c #d horses draw x z fa/8 #c4 ,:at is ! effici5cy ( a motor t is runn+ fa/ b do+ no useful "w8 #d4 ,:at horse-p[] c be _h f a wat]fall1 #ab ft4 high1 if #bj cu4 ft4 ( wat] pass ov] x ea* second8 #e4 ,:at is ! horse-p[] ( a fire eng9e if x c ?r[ #fjj gallons ( wat] a m9ute to a height ( #ajj ft48 #f4 ,:y are und]%ot :eels less effici5t ?an ! ov]%ot :eel or turb9e8 #g4 ,a revolv+ electric fan is plac$ on ! /]n ( a boat4 ,does ! boat move8 ,:y8 ,place ! fan "u wat]4 ,does ! boat n[ move8 ,:y8 #h4 ,:y does an electric fan produce a breeze8 #i4 ,expla9 ! action ( ! bell[s 9 an organ4 #aj4 ,at ,niag>a ,falls ! turb9es are #acf ft4 bel[ ! surface ( ! riv]4 ,_! av]age horse-p[] is #ejjj ea*4 #dcj cu4 ft4 ( wat] ea* second pass ?r\gh ea* turb9e4 ,f9d ! effici5cy4 #aa4 ,at ,laxey on ! ,isle ( ,man is ! l>ge/ ov]%ot :eel n[ 9 use4 ,x has a horse-p[] ( #aej1 a diamet] ( #gb4e ft41 a wid? ( #aj ft41 & an effici5cy ( #he p] c5t4 ,h[ _m cubic feet ( wat] pass ov] x ea* second8 #ab4 ,! p[] plant at ! ,pikes ,peak ,hydro-electric ,company utilizes a head ( #baej ft41 :i* is equal to a pressure ( #ice lbs4 p] squ>e in*1 to run a ,pelton :eel4 ,if ! area ( ! nozzle is #a sq4 94 & ! jet has a velocity ( #bb1cjj ft4 p] m9ute1 :at is ! horse-p[] develop$ if ! effici5cy is #hj p] c5t48 #ac4 ,a te/ made 9 #aiji ( ! turb9es at ! ,c5t]ville p[] h\se ( ! ,cali=nia ,gas & ,electric ,corporation %[$ a maximum horse-p[] ( #igjj1 spe$ #djj r4p4m4 "u a head ( #eej ft4 ,! effici5cy 0 #hf4be p] c5t4 ,h[ _m cubic feet ( wat] pass$ ?r\gh ! turb9es ea* second8 #ad4 ,! turb9e 9 ! ,city ( ,tacoma ,p[] ,plant 7see ,fig4 #abj7 uses a head ( #dae ft4 #ade cu4 ft4 a second pass ?r\gh ! turb9e4 ,calculate ! horse-p[]4 #ae4 ,9 problem #ad1 :at is ! wat] pressure p] squ>e in* at ! turb9e8 #af4 ,! p[] plant m5tion$ 9 problem #ac develops #fjjj kw4 ,:at is ! effici5cy8 ,review ,outl9e3 ,"w & ,en]gy ,"w2 h[ measur$1 units1 foot-p\nd1 kilogram met]1 erg4 ,en]gy2 h[ measur$1 units1 pot5tial1 ,p4,e4 w h1 or f s4 ,k9etic 7wv7_/7#b;g74 ,p[]2 h[ measur$1 units1 horse p[]1 watt1 #e =ms ( en]gy1 cons]vation4 ,h4p4 7lbs4 ft47_/7#eej sec474 ,ma*9es2 #f simple =ms1 #b gr\ps1 advantages1 uses1 ,law3 ,w ,dw ,f ,df4 ,lev]2 mom5ts1 me*anical advantage1 uses & applications4 ,:eel & ,axle & ,pulley2 common applications1 me*anical advantage4 ,incl9$ ,plane1 ,w$ge1 & ,screw2 me*anical advantage & effici5cy4 ,friction2 uses1 h[ r$uc$1 coeffici5t (1 laws 7#c74 ,wat] ,:eels2 types1 effici5cy1 uses4 ,,*apt] ,,vii ,,heat1 ,,its ,,production ,,& ,,transmission 7#a7 ,,s\rces ,,& ,,effects ,,( ,,heat #ach4 ,importance ( ! ,/udy ( ,heat4--,heat is br\ght to our att5tion ?r\gh ! s5sations ( heat & cold4 ,9 w9t]1 we w>m our h\ses & prev5t ! escape ( heat f !m z mu* z possible4 ,9 summ] we endeavor to keep our liv+ rooms cool & our bodies f be+ ov]heat$4 ,a cle> und]/&+ ( ! sev]al s\rces1 effects1 & modes ( transf]r+ heat is ( importance to ev]yone liv+ 9 our complex civilization1 especially :5 we consid] ! multitudes ( objects t h z _! pr9cipal use ! production1 transf] or utilization ( heat4 #aci4 ,pr9cipal ,s\rces ( ,heat4--,fir/ & mo/ important is ! ,sun1 :i* is cont9ually s5d+ to u radiant en]gy 9 ! =m ( light & heat waves4 ,^! w>m ! e>?1 make plants gr[1 evaporate wat]1 besides produc+ _m o!r important effects4 ,second1 *emical en]gy is (t5 trans=m$ into heat4 ,"o has b to ?9k ( ! heat produc$ by burn+ coal1 wood1 oil1 & gas1 to recognize ! importance ( ?is s\rce4 ,*emical en]gy is also ! s\rce ( ! heat produc$ )9 our bodies4 ,! action ( quicklime & wat] ^u ea* o!r produces mu* heat4 ,?is action is sometimes employ$ dur+ balloon trips z a means ( w>m+ ?+s4 ,?ird1 ,electrical ,en]gy4--,9 _m cities electric c>s are heat$ by ! electric curr5t4 ,we h all he>d ( electric toa/]s & o!r devices = heat+ by electricity4 ,electric light is produc$ by ! heat+ ( "s mat]ial to inc&esc5ce by an electric curr5t4 ,! electric furnace has a wide application 9 ! prep>ation & ref9+ ( metals4 ,illu/ration3 ,,fig4 #abj4--;,boy-sc\t me?od ( mak+ fire by friction4 ,f\r?1 heat is also produc$ :5ev] me*anical en]gy ( motion is ov]come1 :e!r x be by friction1 concussion1 or compression4 ,friction always results 9 ! production ( heat1 z :5 we w>m our h&s by rubb+ !m toge!r4 ,:5 friction is excessive1 su* z 9 ! case ( a heavy be>+ n prop]ly oil$1 ! be>+ may get v hot4 ,?is is ! cause ( ! hot box on a railway c>4 ,friction may produce heat en\gh to set wood on fire4 ,"s fires 9 mills are believ$ to be due to ?is cause4 ,e boy sc\t mu/ le>n h[ to produce fire by friction4 7,see ,fig4 #abj47 ,concussion may be illu/rat$ by ! heat+ ( a piece ( metal by hamm]+ x1 :ile ! compression ( a gas always makes x w>m]1 z ^? :o h us$ a bicycle pump h obs]v$4 ,! production ( heat by compress+ a gas is illu/rat$ by ! fire syr+e 7,fig4 #aba74 ,?is consi/s ( a glass tube ) a tightly fitt$ pi/on4 ,a sudd5 compression ( ! air conta9$ may ignite a trace ( c>bon bisulfid vapor4 ,illu/ration3 ,,fig4 #aba4--;,a fire syr+e4 ,! int]ior ( ! e>? is hot1 b its heat seldom gets to ! surface except at hot spr+s & volcanoes4 #adj4 ,! ,effects ( ,heat4--,!re are five important *anges produc$ by heat3 7a7 *ange ( size1 7b7 *ange ( temp]ature1 7c7 *ange ( /ate1 z ! melt+ ( ice or evaporat+ ( wat]1 7d7 *emical *ange1 z ! *>r+ ( sug> :5 x is ov]heat$1 & 7e7 electrical *ange4 ,?is is illu/rat$ by ! production ( an electric curr5t1 by ! heat+ ( ! junction ( two diff]5t metals4 ,a !rmo-electric g5]ator 7see ,fig4 #abb7 has be5 con/ruct$ ^u ?is pr9ciple & works successfully4 ,illu/ration3 ,,fig4 #abb4--;,a !rmo-electric g5]ator4 ,important ,topics #a4 ,importance ( a /udy ( heat4 #b4 ,f\r s\rces ( heat4 #c4 ,five effects ( heat4 #d4 ,examples ( ea*4 #e4 ,illu/rations ( trans=mation ( en]gy :i* involve heat4 ,ex]cises #a4 ,write a li/ ( ! s\rces ( heat 9 ! ord] ( _! importance to y4 ,/ate :y ea* is important to y4 #b4 ,:i* ?ree ( ! effects ( heat d y make mo/ use (8 ,expla9 :at use y make ( ea* ( ^! effects4 #c4 ,:i* ( ! =ms ( en]gy c be trans=m$ into heat8 ,h[ 9 ea* case8 #d4 ,into :at o!r =ms ( en]gy may heat be trans=m$8 ,"n ! device or process us$ 9 ea* case4 #e4 ,:at five diff]5t commodities are pur*as$ by p 9 y\r neighborhood = ! production ( heat8 ,:i* ( ^! co/s lea/ = ! am\nt ( heat furni%$8 ,:i* is mo/ exp5sive8 ,h[ d y det]m9e ^! answ]s8 #f4 ,:y d _m p buy heat 9 an exp5sive =m1 z 9 us+ an electric toa/]1 :5 !y c obta9 x 9 a *eap] =m by burn+ gas or coal8 #g4 ,h[ _m ( ! five effects ( heat h y obs]v$ outside ( s*ool8 7#b7 ,,temp]ature ,,& ,,expansion #ada4 ,heat & ,temp]ature4--,we %\ld n[ cle>ly di/+ui% betwe5 ! t]ms1 heat & temp]ature4 ,heat is a =m ( en]gy consi/+ ( molecul> motion4 ,! temp]ature ( a body is its degree ( hotness4 ,! am\nt ( heat pres5t 9 a body & its temp]ature are v diff]5t ?+s4 ,! temp]ature ref]s to ! int5sity ( ! heat 9 ! body4 ,a qu>t ( wat] & a r$ hot iron ball may conta9 equal am\nts ( heat1 al?\gh ! ball has a mu* high] temp]ature ?an ! wat]4 ,a cup ( boil+ wat] w h ! same temp]ature z a tank full ( boil+ wat]1 b ! tank w conta9 m heat4 ,e "o kn[s t x w take long] to boil a kettle full ( wat] ?an a cupful4 ,a hot-wat] bag1 hold+ #b qu>ts ( wat] w give (f heat long] ?an a #a-qu>t bag1 bo? be+ fill$ ) wat] at ! same temp]ature4 ,to put x 9 ano!r way1 m "w is done 9 heat+ a l>ge am\nt ( wat]1 ?an a small am\nt ?r\gh ! same *ange ( temp]ature4 #adb4 ,units ( ,heat & ,temp]ature4--,!re are two common units = measur+ heat3 ! ,calorie & ! ,briti% !rmal unit4 ,! calorie is ! am\nt ( heat requir$ to raise ! temp]ature ( a gram ( wat] "o c5tigrade degree4 ,! ,briti% !rmal unit is ! am\nt ( heat requir$ to raise ! temp]ature ( "o p\nd ( wat] "o ,fahr5heit degree4 ,"o ( ! units pla9ly belongs to ! metric sy/em1 ! o!r to ! ,engli%4 ,an in/rum5t = measur+ temp]ature is call$ a !rmomet]4 ,v>i\s scales are plac$ ^u !rmomet]s4 ,! two !rmomet] scales mo/ commonly us$ 9 ?is c\ntry are ! ,c5tigrade & ! ,fahr5heit4 ,! ,fahr5heit !rmomet] scale has ! temp]ature ( melt+ ice m>k$ #cb4 ,! boil+ po9t or /eam temp]ature ( pure wat] "u /&>d conditions ( atmosph]ic pressure is m>k$ #bab & ! space betwe5 ^! two fix$ po9ts is divid$ into #ahj p>ts4 ,! c5tigrade !rmomet] scale has ! same fix$ po9ts m>k$ #j & #ajj & ! space betwe5 divid$ into #ajj p>ts4 7,see ,fig4 #abc47 ,! c5tigrade scale is ! "o us$ by sci5ti/s ev]y:]e4 ,illu/ration3 ,,fig4 #abc4--;,comp>ison ( c5tigrade & ,fahr5heit scales4 #adc4 ,comp>ison ( ,!rmomet] ,scales4--,x is (t5 necess>y to express 9 c5tigrade degrees a temp]ature = :i* ! ,fahr5heit read+ is giv5 or vice v]sa4 ,s9ce !re are #ahj ,fahr5heit degrees betwe5 ! fix$ po9ts & #ajj c5tigrade degrees1 ! ,fahr5heit degrees are small] ?an ! c5tigrade1 or #a;,f4 #e_/i;,c4 & #a;,c4 #i_/e;,f4 ,"o mu/ also take into acc\nt ! fact t ! melt+ po9t ( ice on ! ,fahr5heit scale is m>k$ #cb4 ,h5ce ! foll[+ rule3 ,to *ange a ,fahr5heit read+ to c5tigrade subtract #cb & take #e_/i ( ! rema9d]1 :ile to *ange c5tigrade to ,fahr5heit multiply ! c5tigrade by #i_/e & add #cb to ! product4 ,^! two rules are express$ by ! foll[+ =mulas4 7,f4 - #cb7e_/i ,c41 #i;,c4_/#e #cb ,f4 ,ano!r me?od ( *ang+ f "o !rmometric scale to ano!r is z foll[s3 ,a temp]ature ( -#dj;,f4 is also repres5t$ by -#dj;,c41 !re=e to *ange a ,fahr5heit read+ into c5tigrade1 we add #dj to ! giv5 read+1 !n divide by #a4h aft] :i* subtract #dj4 ,to *ange f a c5tigrade to ,fahr5heit read+ ! only diff]5ce 9 ?is me?od is to multiply by #a4h or ,c4 7,f4 #dj7_/a4h - #dj & ,f4 #a4h7;,c4 #dj7 - #dj4 ,illu/ration3 ,,fig4 #abd--;,comp>ison ( absolute1 c5tigrade & ,fahr5heit scales4 #add4 ,! ,absolute ,scale ( ,temp]ature4--,"o (t5 he>s ! /atem5t z cold z ice4 ,?is expresses ! incorrect idea t ice _c become cold] ?an its freez+ temp]ature4 ,! fact is t ice may be cool$ bel[ freez+ d[n to ! temp]ature ( its surr\nd+s4 ,if a piece ( ice is plac$ :]e ! temp]ature is bel[ ! melt+ po9t1 ! ice1 l any o!r solid1 cools to ! temp]ature ( ! surr\nd+ space4 ,= example1 a piece ( ice out ( doors is at #aj;,f4 :5 ! air is at ?is temp]ature4 ,x foll[s !n1 t :5 ice has be5 cool$ bel[ ! freez+ temp]ature t heat is requir$ to w>m ! ice up to its melt+ po9t2 or 9 o!r words t ice at its melt+ temp]ature possesses "s heat4 ,! temp]ature at :i* absolutely no heat exi/s is call$ absolute z]o4 ,!re has be5 devis$ an absolute scale ( temp]ature4 ,?is scale is bas$ ^u ! c5tigrade scale1 i4e41 ) #ajj betwe5 ! two fix$ po9ts2 ! scale1 h[ev]1 ext5ds d[n1 bel[ ! c5tigrade z]o1 #bgc1 to :at is call$ absolute z]o4 ,x foll[s !re=e t ^u ! absolute scale1 ! melt+ po9t ( ice1 & ! boil+ po9t ( wat] are #bgc & #cgc respectively4 7,see ,fig4 #abd47 ,! means employ$ to f9d ! location ( absolute z]o are ( mu* int]e/4 ,x has be5 obs]v$ t :5 heat$ a gas t5ds to exp&4 ,if a measur$ volume ( air at #j;,c4 is cool$ or heat$ #a;,c41 x *anges its volume #a_/bgc1 ! pressure rema9+ ! same4 ,if x is cool$ #aj x loses #aj_/bgc1 if cool$ #ajj x loses #ajj_/bgc & s on4 ,no matt] h[ f> x is cool$ ! same rate ( r$uction cont9ues z long z x rema9s 9 ! gase\s /ate4 ,f ^! facts x is conclud$ t if ! cool+ c\ld be c>ri$ d[n #bgc t ! volume w\ld be r$uc$ #bgc_/bgc or t ! volume ( ! gas w\ld be r$uc$ to no?+4 ,?is is believ$ to mean t ! molecul> motion con/itut+ heat w\ld cease r ?an t ! matt] compos+ ! gas w\ld disappe>4 ,sci5ti/s h be5 able to obta9 temp]atures ( extreme cold f> d[n on ! absolute scale4 ,liquid air has a temp]ature ( -#bib;,f41 or -#ahj;,c4 or #ic;,a4 ,! l[e/ temp]ature ?us f> report$ is #a4g;,a4 or -#bga4c;,c41 obta9$ 9 #aiaa1 by evaporat+ liquid helium4 #ade4 ,! ,law ( ,*>les4--,! facts giv5 9 ! la/ p>agraph mean t if #bgc ccm4 ( a gas at #j;,c4 or #bgc ,a4 are cool$ #ajj1 or to -#ajj;,c41 or #agc;,a41 !n x w lose #ajj_/bgc ( its volume or h a volume ( #agc ccm4 ,if w>m$ #ajj1 or up to #ajj;,c41 or #cgc;,a41 x w h a volume ( #cgc ccm4 ,x foll[s !n t 9 e case ! volume w correspond to its absolute temp]ature1 provid+ ! pressure rema9s un*ang$4 ,! expression ( ?is fact 9 sci5tific language is call$ ! law ( ,*>les4 ,at a con/ant pressure ! volume ( a giv5 mass ( gas is proportional to its absolute temp]ature4 ,express$ ma!matically1 we h ,v#a_/,v#b ,t#a_/,t#b4 ,comp>e ! /atem5t & ma!matical expression ( ! laws ( ,*>les & ,boyle4 ,! =mulas = ! laws ( ,boyle & ,*>les are sometimes comb9$ into "o expression z foll[s3 ,,pv_/,t ,p,v_/,t or ! product ( ! volume & pressure ( a con/ant mass ( gas is proportional to its absolute temp]ature4 ,important ,topics #a4 ,heat units2 calorie1 ,briti% !rmal unit4 #b4 ,?ree !rmomet] scales1 fix$ po9ts on ea*4 #c4 ,absolute z]o1 h[ det]m9$4 ,its value on ea* scale4 #d4 ,law ( ,*>les1 its mean+4 ,comb9ation ( laws ( ,boyle & ,*>les4 ,ex]cises #a4 ,does ice melt at ! same temp]ature at :i* wat] freezes8 ,express ! temp]ature ( freez+ wat] on ! ?ree !rmomet] scales4 #b4 ,a com=table room temp]ature is #fh;,f4 ,:at is ?is temp]ature on ! c5tigrade & absolute scales8 #c4 ,*ange a temp]ature ( #ae;,c4 to ,f42 #ae;,f4 to ,c42 -#d;,c4 to ,f42 -#bj;,f4 to ,c4 #d4 ,! temp]ature ( ! human body is #ih4f;,f4 ,:at is ?is temp]ature on ! absolute & c5tigrade scales8 #e4 ,! temp]ature ( liquid air is -#ahj;,c4 ,:at is x on ! ,fahr5heit scale8 #f4 ,m]cury is a solid at -#dj;,f4 ,:at is ?is on ! c5tigrade scale8 #g4 ,h[ mu* heat w be requir$ to raise ! temp]ature ( #h lbs4 ( wat] #cb;,f42 #e lbs4 #aj;,f48 ,illu/ration3 ,,fig4 #abe4--;,a cl9ical !rmomet] us$ to take ! temp]ature ( ! body4 #h4 ,h[ mu* heat w be requir$ to raise ! temp]ature ( #cj g4 ( wat] #dc;,c42 #bj g41 #ej;,c48 #i4 ,compute ! temp]ature ( absolute z]o on ! ,fahr5heit scale4 #aj4 ,take ?ree bas9s ( wat]1 "o hot1 "o cold1 & "o lukew>m4 ,if "o h& be plac$ 9 ! hot wat] :ile ! o!r is plac$ 9 ! cold & aft] a few m9utes bo? are plac$ 9 ! lukew>m wat]1 ?is wat] w feel cool to "o h& & w>m to ! o!r4 ,expla94 #aa4 ,if #bjj ccm4 ( air at #bjj absolute is heat$ to #cjj;,a4 "u con/ant pressure1 :at volume w ! air occupy at ! latt] temp]ature8 #ab4 ,h[ does "o *ange a read+ on ! c5tigrade scale to a correspond+ read+ on ! absolute scale8 7#c7 ,,expansion ,,( ,,liquids ,,& ,,solids #adf4 ,expansion ( ,gases4--,! law ( ,*>les is f\nd to apply to all gases4 ,t is1 all gases *ange 9 volume 9 proportion to ! *ange ( temp]ature provid$ ! pressure rema9s con/ant4 ,x is = ?is reason t we h ! gas !rmomet] 7see ,fig4 #abf7 :i* gives 9 skillful h&s m accurate temp]ature read+s ?an ! be/ m]curial !rmomet]4 ,galileo devis$ & us$ ! fir/ air !rmomet] :i* consi/$ ( a holl[ bulb bl[n on a glass tube & inv]t$ 9 a di% ( wat]4 7,see ,fig4 #a47 ,! wat] !rmomet] consi/s ( a glass bulb fill$ ) wat] :i* rises into a tube atta*$ to ! bulb4 ,"o disadvantage ( ! wat] !rmomet] is its limit$ range s9ce x _c be us$ bel[ #j or above #ajj4 ,:y8 #adg4 ,expansion ( ,liquids4--,! expansion ( liquids diff]s f t ( gases 9 sev]al important respects3 7a7 ,liquids h a small] rate ( expansion ?an gases4 ,! rate ( expansion p] degree is call$ ! ,coeffici5t ( ,expansion4 ,= example1 ! coeffici5t ( expansion ( a gas "u con/ant pressure at #j;,c4 is #a_/bgc ( its volume p] degree c5tigrade4 7b7 ,diff]5t liquids exp& at :olly diff]5t rates1 t is1 _! coeffici5ts ( expansion diff] widely4 ,= example1 ! coeffici5t ( expansion ( m]cury is #j4jjjah p] degree c5tigrade1 ( glyc]9e #j4jjje p] degree c5tigrade1 ( petroleum #j4jjji p] degree c5tigrade4 ,illu/ration3 ,,fig4 #abf4--;,gas !rmomet]4 7c7 ,! same liquid (t5 has diff]5t coeffici5ts ( expansion at diff]5t temp]atures4 ,wat] betwe5 #e;,c4 & #f;,c4 has a coeffici5t expansion ( #j4jjjjb p] degree c5tigrade1 betwe5 #h & #ej ( #j4jjjf1 betwe5 #ii & #ajj ( #j4jjjgf4 ,! coeffici5t ( expansion ( m]cury1 h[ev]1 is con/ant = a wide range ( temp]ature &1 !re=e1 x is well adapt$ = use 9 !rmomet]s4 #adh4 ,peculi>ity 9 ! ,expansion ( ,wat]4--,wat] has a peculi> rate ( expansion4 ,?is is illu/rat$ by ! foll[+ exp]im5t3 ,a te/-tube fill$ ) cold wat] is clos$ by a /opp] conta9+ a small glass tube1 ! wat] ext5d+ up into ! small tube4 7,see ,fig4 #abg47 ,! te/-tube is plac$ 9 a freez+ mixture ( salt & ice conta9$ 9 a tumbl]4 ,z ! wat] cools1 ! level ( ! wat] 9 ! small tube at fir/ s9ks4 ,b be=e ! wat] freezes x rises aga91 %[+ t aft] ! wat] cools to a c]ta9 temp]ature t expansion ( ! wat] occurs ) fur!r cool+4 ,c>eful te/s %[ t ! wat] on cool+ contracts until x rea*es #d;,c4 ,on cool+ bel[ ?is temp]ature x exp&s4 ,= ?is reason1 :5 ! wat] ( a lake or riv] freezes1 ! colde/ wat] is at ! surface4 ,on acc\nt ( ?is ! ice =ms at ! top in/ead ( at ! bottom4 ,if wat] contract$ z x cool$ to ! freez+ temp]ature ! colde/ wat] w\ld be at ! bottom4 ,freez+ w\ld beg9 at ! bottom in/ead ( at ! surface4 ,lakes & riv]s w\ld freeze solid4 ,9 ! summ] only 9 %all[ wat]s w\ld all ! ice melt4 ,! result w\ld be t fi% & o!r aquatic life w\ld be kill$4 ,climate w\ld be s *ang$ t ! e>? might become un9habitable4 ,s9ce wat] is d5se/ at #d;,c4 all ! wat] 9 a lake or riv]1 :5 x is cov]$ ) ice1 is at #d;,c4 except t ne> ! surface4 ,illu/ration3 ,,fig4 #abg4--;,app>atus us$ 9 te/+ ! expansion ( wat]4 #adi4 ,! ,expansion ,( ,solids4--,mo/ solids :5 heat$ exp& less ?an liquids & gases4 ,c>eful exp]im5ts %[ t expansion is3 7a7 ,proportional to ! *ange 9 temp]ature4 7b7 ,diff]5t 9 diff]5t solids4 ,"h are a few coeffici5ts ( l9e> 7l5g?7 expansion4 ,brass #j4jjjjah p] degree ,c4 ,glass #j4jjjjji p] degree ,c4 ,ice #j4jjjjeb p] degree ,c4 ,iron #j4jjjjab p] degree ,c4 ,plat9um #j4jjjjji p] degree ,c4 ,z9c #j4jjjjbg p] degree ,c4 ,! coeffici5t ( l9e> expansion is ! fraction ( its l5g? t a body exp&s :5 heat$ "o degree4 ,! coeffici5t ( cubical expansion is ! fraction ( its volume t a body exp&s :5 heat$ "o degree4 ,! expansion ( solids is us$ or all[$ = 9 _m cases3 a4 ,jo9ts betwe5 ! rails on a railroad all[ = ! expansion ( ! rails 9 summ]4 b4 ,"o end ( a /eel truss bridge is usually support$ on roll]s s t x c exp& & contract ) *ang+ temp]atures4 7,see ,fig4 #abh47 ,illu/ration3 ,,fig4 #abh4--,truss bridge %[+ roll] support at "o end4 c4 ,susp5sion bridges h expansion jo9ts :]e ! ends ( ! iron gird]s c move 9 or out ( an expansion jo9t ?us mak+ ! bridge long] or %ort] accord+ to ! temp]ature4 d4 ,iron tires are heat$1 slipp$ on to wagon :eels & !n cool$1 ! contraction on cool+ sett+ !m tightly 9 place4 e4 ,metallic !rmomet]s dep5d ^u ! movem5t due to ! expansion ( a coil$ /rip ( metal :i* turns a po9t] on ! dial ( ! in/rum5t4 7,see ,fig4 #abi47 f4 ,! wires t are fus$ into glass 9 inc&esc5t light bulbs mu/ h ! same coeffici5t ( expansion z ! glass4 ,plat9um has !re=e be5 us$ = ?is purpose4 7,see table above47 ,illu/ration3 ,,fig4 #abi4--,metallic !rmomet]4 ,important ,topics #a4 ,expansion ( ,liquids2 peculi>ities4 ,anomal\s expansion ( wat] & its results4 #b4 ,expansion ( solids2 peculi>ities1 applications4 #c4 ,coeffici5t ( l9e> expansion4 #d4 ,coeffici5t ( cubical expansion4 ,ex]cises #a4 ,! gas )9 a p>tly inflat$ balloon has a volume ( #ajjj cu4 ft4 at a pressure ( #gd cm41 & a temp]ature ( #ae;,c4 ,:at w be ! volume ( ! gas :5 its pressure is #cg cm4 & ! temp]ature is -#ag;,c48 #b4 ,a man tak+ a full brea? on ! top ( a m\nta9 f\rte5 ?\s& feet high inhales #d lit]s ( air1 ! pressure be+ #dj cm4 ,:at volume w\ld ?is same mass ( air h 9 a place #fjj ft4 above sea-level :5 ! b>omet] reads #ge cm4 & ! temp]ature is ! same z on ! m\nta9 top8 #c4 ,if ! coeffici5t ( l9e> expansion ( iron is #j4jjjjab p] degree ,c41 h[ mu* w an iron bridge #ajjj ft4 long *ange 9 l5g? 9 w>m+ f -#bj;,c4 on a w9t] day to #cj;,c4 ^u a summ] day4 #d4 ,:at are "s ( ! results t w\ld foll[ 9 freez+ wea!r if wat] cont9ually contract$ on be+ cool$ to z]o in/ead ( beg9n+ to exp& :5 cool$ bel[ #d;,c48 #e4 ,m5tion two in/ances t y h notic$ ( expansion occurr+ :5 a body is heat$8 #f4 ,comp>e ! d5sity ( air at #cj;,c4 ) t at #aj;,c4 at ! same pressure4 ,if bo? are pres5t 9 a room1 :]e w ea* be f\nd8 ,:y8 #g4 ,comp>e ! d5sity ( wat] at #dj;,c4 ) t at #aj;,c4 ,if wat] at ! two temp]atures are 9 a tank1 :]e w ea* be f\nd8 ,:y8 #h4 ,if wat] at #j;,c4 & at #d;,c4 are bo? 9 a tank1 :]e w ea* be f\nd8 ,:y8 #i4 ,h[ mu* heat w be requir$ to raise ! temp]ature ( a cubic foot ( wat] #aj;,f48 #aj4 ,h[ mu* heat w be requir$ to raise ! temp]ature ( #d lit]s ( wat] #be;,c48 #aa4 ,h[ mu* long] w\ld ! cables ( ! ,brooklyn susp5sion bridge be on a summ]'s day :5 ! temp]ature is #cj;,c4 ?an 9 w9t] at -#bj;,c41 ! l5g? ( cable betwe5 ! supports be+ ab\t #afjj ft4 #ab4 ,if #be lit]s ( air at -#bc;,c4 is w>m$ to #gg;,c4 "u con/ant pressure1 :at w be ! result+ volume ( air8 ,expla94 #ac4 ,:ite pig iron melts at ab\t #bjjj;,f4 ,express ?is temp]ature ^u ! c5tigrade & absolute scales4 #ad4 ,if #bjj ccm4 ( air at #gf cm4 pressure & #bg;,c4 temp]ature be heat$ to #abg;,c4 at a pressure ( #ch cm4 :at w be ! result+ volume8 #ae4 ,a balloon conta9s #aj1jjj cu4 ft4 ( gas at #ge4b cm4 pressure & #bd;,c4 ,x asc5ds until ! pressure is #ah cm4 & ! temp]ature is -#aj;,c4 ,:at is ! volume ( gas x !n conta9s4 #af4 ,a gas hold] conta9s #ej cu4 ft4 ( gas at a pressure ( "o atmosph]e & #fb;,f4 ,h[ mu* gas w x hold at #aj atmosph]es & #cb;,f4 #ag4 ,"o ?\s& cubic feet ( illum9at+ gas has :at volume ) #ge lbs4 pressure & temp]ature ( #aj;,c4 #ah4 ,def9e a cubic foot ( illum9at+ gas4 #aej4 ,me?ods ( ,transmitt+ ,heat4--,"o ( ! mo/ practical b5efits ( ! /udy ( heat is cle>] und]/&+ ( ! diff]5t me?ods by :i* heat is transf]r$ f "o place to ano!r & an intellig5t idea ( ! means employ$ to prev5t ! transf] ( heat4 ,x %\ld be def9itely und]/ood at ! beg9n+ t cold signifies ! abs5ce ( heat1 j z d>kness implies ! abs5ce ( light1 s :5 "o speaks ( cold gett+ into a h\se :at is really meant is ei!r ! entrance ( cold air by "s op5+ or else ! escape ( ! heat4 ,!re are ?ree di/9ct me?ods by :i* heat en]gy is transf]r$ f "o place to ano!r1 dep5d+ ^u ! m$ium or sub/ance t transf]s ! heat4 a4 ,a solid transmits heat by ! me?od call$ conduction4 b4 ,a fluid1 ei!r a liquid or a gas1 transmits heat ma9ly by ! me?od call$ convection4 c4 ,space transmits ! en]gy ( hot objects by ! me?od call$ radiation4 ,illu/ration3 ,,fig4 #acj4--,solids conduct heat4 #aea4 ,conduction4--,to illu/rate conduction1 place 9 a gas flame ! ends ( same metal wires support$ z 9 ,fig4 #acj4 ,9 a %ort "t ! o!r ends ( ! wires become hot en\gh to burn "o's h&4 ,?is may be expla9$ z foll[s3 ,! hot gas flame conta9s molecules 9 viol5t vibration & ^? /rik+ ! wire set its molecules rapidly vibrat+4 ,s9ce1 9 a solid1 ! molecules are held 9 ! same relative positions1 :5 "o end ( a wire is heat$ ! rapidly vibrat+ molecules at ! hot end set _! neighbors vibrat+ & ^! ! next 9 turn & s on until ! :ole wire is hot4 ,x is a =tunate circum/ance t diff]5t sub/ances h diff]5t rates ( conductivity = heat4 ,to realize ?is1 suppose t our clo?+ 7 z good a conductor z iron1 clo?+ w\ld !n be v uncom=table bo? 9 hot & 9 cold wea!r4 ,! be/ conductors = heat are metals4 ,x is int]e/+ to note t1 z a rule good conductors ( heat are also good conductors ( electricity1 :ile poor conductors ( heat are also poor electric conductors4 ,c>eful exp]im5ts 9 te/+ ! rate t heat w be conduct$ ?r\gh diff]5t sub/ances %[ ! foll[+ rates ( conductivity4 ,illu/ration3 ,,fig4 #aca4--,wat] is a poor conductor ( heat4 ,^! figures are av]ages tak5 ma9ly f ! ,smi?sonian ,physical ,tables3 ,silv] #ajj ,copp] #gd ,alum9um #ce ,brass #bg ,z9c #bf ,iron #ae ,t9 #ad4g ,g]man silv] #h4d ,m]cury #a4g ,granite #j4ec ,lime/one #j4eb ,ice #j4e ,glass #j4b ,wat] #j4abd ,p9e1 ) gra9 #j4jc ,p9e1 across gra9 #j4ja ,felt #j4jjh ,air #j4jje ,to te/ ! conductivity ( liquids1 take a te/-tube ne>ly full ( cold wat]1 hold ! l[] end 9 ! h& :ile ! tube is incl9$ s t ! upp] end is heat$ by a gas flame until ! wat] boils4 ,! l[] end w be f\nd to rema9 cold4 7,see ,fig4 #aca47 ,c>eful measurem5ts ( ! conductivity ( wat] %[ t heat is transmitt$ ?r\gh x only #a_/hjj z rapidly z 9 silv]1 :ile air conducts b #a_/be z rapidly z wat]4 ,illu/ration3 ,,fig4 #acb4--,wall con/ruction ( a refrig]ator4 #a1 ,porcela9 enamel l9+ lock jo9t2 #b1 inside wood l9+2 #c1 #c-ply r$ rope wat]pro( pap]2 #d1 wool felt deaf5+ pap]2 #e1 flaxl9um insulation2 #f1 dead air space2 #g1 flaxl9um insulation2 #h1 wool felt deaf5+ pap]2 #i1 #c-ply r$ rope wat]pro( pap]2 #aj1 outside wood case4 ,illu/ration3 ,,fig4 #acc4--,sectional view ( a ,!rmos bottle4 #aeb4 ,non-conductors & ,_! ,uses4--,_m solids1 h[ev]1 are poor conductors1 z lea!r1 fur1 felt1 & wool5 clo?4 ,^! sub/ances owe _! non-conductivity ma9ly to ! fact t !y are por\s4 ,! air :i* fills ! m9ute spaces ( ^! sub/ances is "o ( ! poore/ conductors kn[n & h9d]s ! transf] ( heat ?r\gh ^! solids4 ,= ! same reason loosely pack$ sn[ is a protection to vegetation cov]$ by x dur+ a p]iod ( sev]e cold 9 w9t]4 ,! effici5cy ( /orm sa% or d\ble w9d[s1 & ( ! d\ble & triple walls ( ice-h\ses & refrig]ators 7see ,fig4 #acb7 9 prev5t+ ! conduction ( heat is also l>gely due to ! poor conductivity ( ! air conf9$ 9 ! spaces betwe5 ! walls4 ,to prev5t ! circulation ( ! air1 sawdu/1 *>coal1 & o!r por\s mat]ial is (t5 loosely pack$ into ! space betwe5 ! walls ( su* /ructure4 ,o!r illu/rations ( effective non-conductors w occur to e "o2 su* z wool5 clo?+1 wood5 h&les = hot objects1 & ! pack+ us$ 9 fireless cook]s4 ,a ,!rmos bottle is effective z a non-conductor ( heat because ! space betwe5 ! d\ble walls has ! air exhau/$ f x 7,figs4 #acc & #acd74 ,( sev]al objects 9 a cold room1 "s feel mu* cold] to ! t\* ?an o!rs1 ?us iron1 m>ble1 oil clo?1 & e>!nw>e w feel cold] ?an wool5 clo?1 c>pet1 fea!rs1 or pap]4 ,! fir/ f\r objects feel cold because !y are conductors1 & conduct ! heat away f ! h& rapidly4 ,! o!r sub/ances nam$ are non-conductors & h5ce remove heat f ! h& less rapidly1 & !re=e d n feel s cold4 ,9 a simil> way1 if sev]al hot objects are t\*$ by ! h&1 ! good conductors are ! ones :i* w burn "o mo/ quickly by conduct+ heat rapidly to ! h&4 ,! non-conductors1 h[ev]1 w r>ely burn "o4 ,:y are ! h&les ( hot ut5sils (t5 made ( non-conduct+ mat]ials su* z wood1 clo?1 asbe/os1 etc48 ,illu/ration3 ,,fig4 #acd4--;,cross-section ( ! vacuum flask 9 a ,!rmos bottle4 #aec4 ,radiation is ! me?od by :i* heat comes to u f ! sun across space conta9+ no tangible matt]4 ,x is also ! me?od by :i* heat gets to u :5 we /& ne> a fire4 ,ev]yone has notic$ t ?is heat is cut (f by hold+ an object betwe5 ! p]son & ! fire4 ,?is fact indicates t radiant heat travels 9 /raight l9es4 ,! radiation ( heat is believ$ to be accompli%$ by means ( waves 9 a m$ium call$ e!r1 :i* is invisible & yet p]vades ev]y?+4 ,?ree ( ! mo/ important *>act]i/ics ( radiation are fir/1 heat is transf]r$ by radiation ) ! spe$ ( light1 or #ahf1jjj miles p] second4 ,?is fact is %[n by ! cutt+ (f ( bo? ! sun's heat & light at ! same in/ant dur+ an eclipse ( ! sun4 ,second1 radiant heat,i travels 9 /raight l9es1 :ile o!r modes ( transf]r+ heat may foll[ irregul> pa?s4 ,! /raight l9e motion ( radiant heat is %[n by its be+ cut (f :]e a scre5 is plac$ betwe5 ! s\rce ( heat & ! object %elt]$4 ,?ird1 radiant heat may pass ?r\gh an object )\t heat+ x4 ,?is is %[n by ! coldness ( ! upp] lay]s ( ! atmosph]e & also by ! fact t a pane ( glass may n be heat$ appreciably by ! heat & light f ! sun :i* passes ?r\gh x4 ,i ,radiant heat is really radiant en]gy & becomes heat :5 x is absorb$ by a body4 ,:5 radiant en]gy falls ^u any object x may be 7a7 reflect$ at ! surface ( ! object1 7b7 transmitt$ ?r\gh ! sub/ance1 7c71 absorb$4 ,all ?ree ( ^! effects occur 9 diff]5t degrees ) diff]5t portions ( ! radiation4 ,well-poli%$ surfaces are good reflectors4 ,r\gh & black5$ surfaces are good absorb]s4 ,transp>5t objects are ^? :i* transmit light well1 b ev5 !y absorb "s ( ! en]gy4 #aed4 ,! ,radiomet]4--,radiant heat may be detect$ by means ( ! radiomet] 7,fig4 #ace74 ,?is consi/s ( a glass bulb f :i* ! air has be5 ne>ly exhau/$4 ,)9 x is a :eel ) f\r vanes ( mica or ( alum9um m\nt$ on a v]tical axis4 ,"o side ( ea* vane is cov]$ ) lampblack1 ! o!r be+ highly poli%$4 :5 expos$ to radiant heat f any s\rce ! vanes revolve ) ! bright side 9 advance4 ,! bulb is s ne>ly exhau/$ ( air t a s+le molecule rema9+ may travel f ! walls ( ! bulb to ! vanes )\t com+ 9 contact ) ano!r molecule4 ,! black5$ sides absorb m heat ?an ! highly poli%$ sides4 ,! air molecules /rik+ ^! black5$ sides receive m heat & s reb\nd ) great] velocity ?an f ! o!r side1 ?us ex]t+ great] pressure4 ,! black5$ sides !re=e are driv5 backw>d4 ,if ! air 7 n s r>ifi$ ! air molecules w\ld hit ea* o!r s frequ5tly z to equalize ! pressure & !re w\ld be no motion4 ,illu/ration3 ,,fig4 #ace4--;,a radiomet]4 ,sun's ,radiation4--,accurate te/s ( ! am\nt ( ! sun's radiation receiv$ ^u a squ>e c5timet] ( ! e>?'s surface p]p5dicul> to ! sun's rays 7 made at ,mt4 ,wilson 9 #aiac4 ,! av]age ( #fij obs]vations gave a value ( #a4icc calories p] m9ute4 ,^! results indicate t ! sun's radiation p] squ>e c5timet] is suffici5t to w>m #a g4 ( wat] #a4icc;,c4 ea* m9ute4 ,al?\gh ! nature ( radiation is n discuss$ until ,art4 #djh-daa 9 light1 x %\ld be said "h t all bodies are radiat+ heat waves at all temp]atures1 ! heat waves f cool bodies be+ mu* long] ?an ^? f hot bodies4 ,glass all[s ! %ort lum9\s waves to pass ?r\gh freely b ! long] heat waves f objects at ! room temp]ature pass ?r\gh ) difficulty4 ,?is is ! reason :y glass is us$ 9 ! cov]+ ( gre5h\ses & hot b$s4 ,wat] also absorbs _m ( ! long] heat waves4 ,x is !re=e us$ 9 /]eopticons to prev5t delicate lant]n slides f be+ injur$ by ov]heat+4 ,important ,topics #a4 ,conduction 9 solids1 liquids1 gases4 #b4 ,non-conductors2 uses1 be/ non-conductors4 #c4 ,radiation1 ?ree *>act]i/ics4 #d4 ,! sun's radiation1 am\nt4 ,! radiomet]4 ,ex]cises #a4 ,does clo?+ ev] af=d u heat 9 w9t]8 ,h[ !n does x keep u w>m8 #b4 ,:y are plants (t5 cov]$ ) pap] on a night :5 fro/ is expect$8 #c4 ,w fro/ =m 9 ! fall ( ! ye> soon] on a wood5 or a cem5t sidewalk8 ,:y8 ,on :i* does ice rema9 long]8 ,:y8 #d4 ,:y 9 freez+ ice-cream d we put ! ice 9 a wood5 pail & ! cream 9 a t9 "o8 #e4 ,is iron bett] ?an brick or porcela9 z a mat]ial = /oves8 ,expla94 #f4 ,:i* is bett]1 a good or a poor conductor = keep+ a body w>m8 = keep+ a body cool8 #g4 ,%\ld ! bottom ( a teakettle be poli%$8 ,expla94 #h4 ,h[ are safes made firepro(8 #i4 ,expla9 ! pr9ciple ( ! ,!rmos bottle4 #aj4 ,expla9 :y ! coil$ wire h&les ( "s objects z /ove-lid lift]s1 ov5 doors1 etc41 d n get hot4 7#e7 ,,transmission ,,( ,,heat ,,9 ,,fluids4 ,,heat+ ,,& ,,v5tilation #aee4 ,convection4--,:ile fluids are poor conductors1 !y may transmit heat m effectively ?an solids by ! mode call$ convection4 ,to illu/rate3 if heat is appli$ at ! top ( a te/-tube ( wat]1 ! hot wat] be+ light] is f\nd at ! top1 :ile at ! bottom ! wat] rema9s cold4 ,on ! o!r h&1 if heat is appli$ at ! bottom ( ! vessel1 z soon z ! wat] at ! bottom is w>m$ 7above #d;,c47 x exp&s1 becomes light] & is pu%$ up to ! top by ! cold]1 d5s] wat] ab\t x4 ,?is circulation ( wat] cont9ues z long z heat is appli$ bel[1 until all ( ! wat] is br\ght to ! boil+ temp]ature4 7,see ,fig4 #acf47 ,:5 a liquid or a gas is heat$ 9 ! mann] j describ$1 ! heat is said to be transf]r$ by convection4 ,?us ! air 9 ! l[] "p ( a room may receive heat by conduction f a /ove or radiator4 ,z x exp&s on be+ w>m$1 x is pu%$ up by ! cold] d5s] air ab\t x1 :i* takes its place1 ?us creat+ a circulation ( ! air 9 ! room4 7,see ,fig4 #acg47 ,! heat$ curr5ts ( air give up _! heat to ! objects 9 ! room z ! circulation cont9ues4 ,^! air curr5ts may be obs]v$ readily by us+ ! smoke f burn+ t\* pap] 7unglaz$ pap] t has be5 dipp$ into a solution ( potassium nitrate saltpet] & dri$74 ,illu/ration3 ,,fig4 #acf4--;,convection 9 a liquid4 #aef4 ,draft ( a ,*imney4--,:5 a fire is />t$ 9 a /ove or a furnace ! air above ! fire becomes heat$1 exp&s1 & !re=e is less d5se ?an x 0 be=e4 ,?is w>m air & ! heat$ gases :i* are ! products ( ! combu/ion ( ! fuel weigh less ?an an equal volume ( ! cold] air outside4 ,!re=e !y are pu%$ upw>d by a =ce equal to ! diff]5ce betwe5 _! weight & ! weight ( an equal volume ( ! cold] air4 ,! *imney soon becomes fill$ ) ^! heat$ gases4 7,see ,fig4 #ach47 ,^! are pu%$ upw>d by ! pressure ( ! cold]1 d5s] air1 because ?is cold] air is pull$ d[nw>d m /rongly by ! =ce ( gravity ?an are ! heat$ gases 9 ! *imney4 ,o!r ?+s be+ equal1 ! tall] ! *imney1 ! great] ! draft1 because !re is a great] diff]5ce betwe5 ! weight ( ! gases inside & ! weight ( an equal volume ( outside air4 ,illu/ration3 ,,fig4 #acg4--;,convection curr5ts 9 a room4 ,illu/ration3 ,,fig4 #ach4--;,fire place %[+ draft ( a *imney4 #aeg4 ,convection ,curr5ts 9 ,nature4--,w9ds are produc$ by diff]5ces 9 ! pressure or d5sity ( ! air1 ! movem5t be+ f places ( high t[>d places ( l[ pressure4 ,"o ( ! causes ( a diff]5ce 9 d5sity ( ! air is a diff]5ce 9 temp]ature4 ,?is is illu/rat$ by :at are call$ ! l& & sea breezes along ! sea %ore or l>ge lakes4 ,dur+ ! day1 ! temp]ature ( ! l& becomes high] ?an t ( ! sea4 ,! air ov] ! l& exp&s & be+ light] is mov$ back & upw>d by ! cold]1 d5s] air f ! sea or lake4 ,?is con/itutes ! sea breezes 7,fig4 #aci74 ,at night ! l& becomes cool] mu* soon] ?an ! sea & ! curr5t is rev]s$ caus+ ! l& breeze4 7,see ,fig4 #adj47 ,illu/ration3 ,,fig4 #aci4--,sea breeze4 ,illu/ration3 ,,fig4 #adj4--,l& breeze4 ,! trade w9ds are convection curr5ts mov+ t[>d ! hot equatorial belt f bo? ! nor? & ! s\?4 ,9 ! hot belt ! air rises & ! upp] air fl[s back to ! nor? & ! s\?4 ,?is region ( asc5d+ curr5ts ( air is a region ( heavy ra9fall1 s9ce ! saturat$ air rises to cool altitudes :]e its moi/ure is cond5s$4 ,! ocean curr5ts are also convection curr5ts4 ,_! motion is due to prevail+ w9ds1 diff]5ces 9 d5sity due to evaporation & freez+1 & to ! rotation ( ! e>?1 z well z to *anges 9 temp]ature4 #aeh4 ,! heat+ & v5tilation ( build+s & ! problems connect$ !re) are matt]s ( s]i\s conc]n to all :o live 9 w9t] 9 ! temp]ate zone4 ,n only %\ld ! air 9 liv+ rooms be com=tably heat$1 b x %\ld be cont9ually *ang$ especially 9 ! cr[d$ rooms ( public build+s1 z ^? ( s*ools1 *ur*es1 & assembly halls1 s t ea* p]son may be suppli$ ) #cj or m cubic feet ( fre% air p] m9ute4 ,9 ! colonial days1 ! op5 fire place af=d$ ! ord9>y means = heat+ rooms4 ,?is heat$ ! room ma9ly by radiation4 ,x 0 wa/eful z mo/ ( ! heat pass$ up ! *imney4 ,?is mode ( heat+ secur$ ample v5tilation4 ,fire places are sometimes built 9 mod]n homes z an aid to v5tilation4 ,b5jam9 ,frankl9 see+ ! wa/e ( heat 9 ! op5 fire places devis$ an iron box to conta9 ! fire4 ,?is 0 plac$ 9 ! room & provid$ heat by conduction1 convection1 & radiation4 ,x 0 call$ ,frankl9's /ove & 9 _m =ms is /ill commonly us$4 ,x saves a l>ge "p ( ! heat produc$ by burn+ ! fuel & "s v5tilation is provid$ by its draft4 ,illu/ration3 ,,fig4 #ada4--;,heat+ & v5tilat+ by means ( a hot-air furnace4 #aei4 ,heat+ by ,hot ,air4--,! pres5ce ( /oves 9 liv+ rooms ( homes is accompani$ by ! annoyance ( scatt]$ fuel1 du/1 a%es1 smoke1 etc4 ,"o attempt to remove ?is inconv5i5ce l$ to plac+ a l>ge /ove or fire box 9 ! basem5t or cell>1 surr\nd+ ?is ) a jacket to provide a space = heat+ air :i* is !n conduct$ by pipes to ! rooms above4 ,?is device is call$ ! hot-air furnace4 7,see ,fig4 #ada47 ,! heat$ air rises because x is pu%$ up by cold]1 d5s] air :i* ent]s ?r\gh ! cold-air pipes4 ,! hot-air furnace provides a good circulation ( w>m air & also v5tilation1 provid$ "s cold air is admitt$ to ! furnace f ! outside4 ,"o objection to its use is t x may n heat a build+ ev5ly1 "o "p be+ v hot :ile ano!r may be cool4 ,to provide ev5 & suffici5t heat ?r\gh\t a l>ge build+1 use is made ( hot wat] or /eam heat+4 ,illu/ration3 ,,fig4 #adb4--;,a hot-wat] sy/em ( heat+4 ,illu/ration3 ,,fig4 #adc4--,"o-pipe sy/em ( /eam heat+4 #afj4 ,hot-wat] ,heat+4--,9 hot-wat] heat+ a furnace arrang$ = heat+ wat] is plac$ 9 ! basem5t4 7,see ,fig4 #adb47 ,atta*$ to ! top ( ! heat] are pipes lead+ to ! radiators 9 ! v>i\s rooms2 o!r pipes connect ! radiators to ! bottom ( ! boil]4 ,! heat]1 pipes1 & radiators are all fill$ ) wat] be=e ! fire is />t$4 ,:5 ! wat] is w>m$1 x exp&s & is pu%$ up ?r\gh ! pipes by ! cold] wat] 9 ! return pipe4 ,! circulation cont9u+ br+s hot wat] to ! radiator :ile ! cool$ wat] returns to ! heat]1 ! hot radiators heat+ ! sev]al rooms4 #afa4 ,/eam ,heat+4--,9 /eam heat+ a /eam boil] is connect$ to radiators by pipes4 7,see ,fig4 #adc47 ,! /eam drives ! air out ( ! pipes & radiators & s]ves z an effici5t s\rce ( heat4 ,heat+ by /eam is quick] ?an heat+ ) hot wat]4 ,x is !re=e pref]r$ :]e quick1 effici5t heat+ is requir$4 ,hot wat] is less int5se & m economical 9 mild wea!r & is (t5 us$ 9 private homes4 ,illu/ration3 ,,fig4 #add4--;,heat+ by an indirect radiator ) side-wall regi/]4 #afb4 ,direct & ,indirect ,heat+4--,9 heat+ by direct radiation 7,figs4 #adb1 #adc71 ! /eam or hot-wat] radiators are plac$ 9 ! rooms to be heat$4 ,) direct radiation1 v5tilation mu/ be provid$ by special means1 su* z op5+ w9d[s1 doors1 & v5tilators4 ,sometimes radiators are plac$ 9 a box or room 9 ! basem5t4 ,air f out ( doors is !n driv5 by a fan ov] & ab\t ! hot radiators4 ,! air ?us heat$ is conduct$ by pipes to ! sev]al rooms4 ,?is arrangem5t is call$ indirect heat+4 7,see ,fig4 #add47 ,! latt] me?od1 x may be obs]v$1 provides bo? heat & v5tilation1 & h5ce is (t5 us$ 9 s*ools1 *ur*es1 c\rt h\ses1 & /ores4 ,s9ce heat$ air1 especially 9 cold wea!r1 has a l[ relative humidity "s means ( moi/5+ ! air ( liv+ rooms %\ld be provid$4 ,air :5 too dry is injuri\s to ! heal? & also to furniture & wood "w4 ,! excessive dry+ ( wood & glue 9 a piece ( furniture (t5 causes x to fall ap>t4 ,illu/ration3 ,,fig4 #ade4--;,an automatic air valve4 ,illu/ration3 ,,fig4 #adf4--;,an automatic vacuum valve4 #afc4 ,vacuum ,/eam ,heat+4--,9 /eam heat+1 air valves 7,fig4 #ade7 are plac$ on ! radiators to all[ ! air !y conta9 to escape :5 ! /eam is turn$ on4 ,:5 all ! air is driv5 out ! valve closes4 ,automatic vacuum valves 7,fig4 #adf7 are sometimes us$4 ,:5 ! fire is l[ & !re is no /eam pressure 9 ! radiators ! pressure ( ! air closes ! valve1 mak+ a p>tial vacuum inside4 ,! boil+ po9t ( wat] falls z ! pressure ^u x is r$uc$4 ,z wat] w n boil "u ord9>y atmosph]ic pressure until its temp]ature is #ajj;,c4 7#bab;,f471 x foll[s t by ! use ( vacuum sy/ems1 (t5 call$ vapor sy/ems1 ( /eam heat+1 wat] w be giv+ (f hot vapor ev5 aft] ! fire has be5 bank$ = h\rs4 ,?is results 9 a consid]able sav+ ( fuel4 ,illu/ration3 ,,fig4 #adg4--,pl5um hot-bla/ sy/em ) temp]ature regulation4 #afd4 ,! ,pl5um ,sy/em ( ,heat+4--,9 ! pl5um sy/em ( heat+ 7see ,fig4 #adg7 fre% air is drawn ?r\gh a w9d[ f outdoors & goes fir/ ?r\gh temp]+ coils :]e ! temp]ature is rais$ to ab\t #gj4 ,! fan !n =ces "s ( ! air ?r\gh heat+ coils1 :]e x is reheat$ & rais$ to a mu* high] temp]ature1 dep5d+ ^u ! wea!r conditions4 ,bo? ! hot & temp]$ air are kept "u pressure by ! fan 9 ! pl5um room & are =c$ f ?is room ?r\gh galvaniz$ iron ducts to ! v>i\s rooms to be heat$4 ,! f\l air is =c$ out ( ! room ?r\gh v5t ducts :i* lead to ! attic :]e x escapes ?r\gh v5tilators 9 ! ro(4 ,illu/ration3 ,,fig4 #adh4--;,a !rmo/at4 7,johnson ,sy/em47 ,a !rmo/at is plac$ 9 ! temp]$-air "p ( ! pl5um room to ma9ta9 ! prop] temp]ature ( ! temp]$ air4 ,?is !rmo/at op]ates ! by-pass damp] "u ! temp]+ coils1 & sometimes ! valves on ! coils4 ,! mix+ damp]s at ! base ( ! galvaniz$-iron ducts are controll$ by _! respective room !rmo/ats4 ,attic-v5t1 fre%-air1 & return-air damp]s are "u pneumatic swit* control4 ,a humidifi] c be provid$ readily = ?is sy/em4 ,?is sy/em ( heat+ is design$ p>ticul>ly = s*ool h\ses :]e adequate v5tilation is a necessity4 #afe4 ,! ,!rmo/at4--,"o ( ! _m examples ( ! expansion ( metals is %[n 9 "o =m ( ! !rmo/at 7,fig4 #adh7 9 :i* two pieces ( diff]5t metals & ( unequal rates ( expansion1 z brass & iron1 are securely fa/5$ toge!r4 ,! !rmo/atic /rip ,t mov+ inw>d & outw>d1 z affect$ by ! room temp]ature1 v>ies ! am\nt ( air :i* c escape ?r\gh ! small port ,c4 ,:5 ! port ,c is completely clos$ 7,fig4 #adh;a7 ! full air pressure collects on ! diaphragm ,b :i* =ces d[n ! ma9 valve1 lett+ ! compress$ air f ! ma9 pass ?r\gh ! *amb] ,d into *amb] ,e z ! valve is =c$ (f its seat4 ,! air f *amb] ,e !n passes into ! bran* to op]ate ! damp]4 ,:5 port ,c is fully op5 7,fig4 #adh;b7 ! air pressure on diaphragm ,b is reliev$1 ! back pressure 9 ,e lifts up ! diaphragm & ! air f ! bran* escapes out ?r\gh ! holl[ /em ( ! ma9 valve1 op]at+ ! damp] 9 ! opposite direction f t :5 ,c is clos$4 ,important ,topics #a4 ,transmission ( heat 9 fluids4 #b4 ,convection4 ,drafts ( a *imney4 ,l& & sea breezes4 #c4 ,heat+ & v5tilation ( build+s4 7a7 ,by hot air4 7b7 ,hot-wat] heat+4 7c7 ,/eam heat+4 7d7 ,direct & indirect heat+4 7e7 ,vacuum /eam heat+4 7f7 ,! pl5um sy/em4 7g7 ,! !rmo/at4 ,ex]cises #a4 ,is a room heat$ ma9ly by conduction1 convection1 or radiation1 f 7a7 a /ove1 7b7 a hot-air furnace1 7c7 a /eam radiator8 #b4 ,"n ?ree natural convection curr5ts4 #c4 ,expla9 ! draft ( a *imney4 ,:at is x8 ,:y does x occur8 #d4 ,make a cross-section sket* ( y\r liv+ room & indicate ! convection curr5ts by :i* ! room is heat$4 ,expla9 ! heat+ ( ! room4 #e4 ,make a sket* %[+ h[ ! wat] 9 ! hot-wat] tank 9 ! kit*5 or laundry is heat$4 ,expla9 y\r sket*1 indicat+ convection curr5ts4 #f4 ,is x economical to keep /oves & radiators highly poli%$8 ,expla94 #g4 ,if y op5 ! door betwe5 a w>m & a cool room :at w be ! direction ( ! air curr5ts at ! top & at ! bottom ( ! door8 ,expla94 #h4 ,if a hot-wat] heat+ sy/em conta9s #ajj cu4 ft4 ( wat] h[ mu* heat w be requir$ to raise its temp]ature #aej;,f48 #i4 ,:y does a tall *imney give a bett] draft ?an a %ort "o8 #aj4 ,expla9 h[ y\r s*ool room is heat$ & v5tilat$4 #aa4 ,%\ld a /eam or hot-wat] radiator be plac$ ne> ! floor or ne> ! ceil+ ( a room8 ,:y8 #ab4 ,9 a hot-wat] heat+ sy/em an op5 tank connect$ ) ! pipes is plac$ 9 ! attic or above ! highe/ radiator4 ,expla9 its use4 7#f7 ,,! ,,moi/ure ,,9 ,,! ,,atmosph]e1 ,,hygrometry #aff4 ,wat] ,vapor 9 ! ,air4--,! am\nt ( wat] vapor pres5t 9 ! air has a m>k$ effect ^u ! wea!r & ! climate ( a locality4 ,! /udy ( ! moi/ure conditions ( ! atmosph]e1 or hygrometry1 is !re=e a matt] ( g5]al int]e/ & importance4 ,! wat] vapor 9 ! atmosph]e is entirely due to evaporation f bodies ( wat]1 or sn[1 or ice4 ,9 ! discussion ( evaporation1 x is describ$ z due to ! gradual escape ( molecules into ! air f ! surface ( a liquid4 ,?is description fits exactly ! conditions f\nd by all c>eful obs]v]s4 ,s9ce ! air molecules are cont9ually /rik+ ! surface ( ! liquid1 _m ( !m p5etrate x & become absorb$4 ,9 ! same mann] _m vapor molecules re5t] ! liquid1 & if en\gh vapor molecules are pres5t 9 ! air s t z _m vapor molecules re5t] ! liquid ea* second z leave x1 ! space above ! liquid is said to be saturat$ z previ\sly describ$4 7,see ,art4 #ah47 #afg4 ,conditions = ,saturation4--,if a liquid is evaporat+ into a vacuum1 ! molecules on leav+ f9d no opposition until !y rea* ! limits ( ! vessel conta9+ ! vacuum4 ,evaporation "u ^! conditions goes on ) great rapidity & ! space becomes saturat$ almo/ in/antly4 ,if1 h[ev]1 air be pres5t at ord9>y pressure1 _m ( ! ord9>y wat] vapor molecules on leav+ are /ruck & return$ to ! wat] by ! air molecules directly above4 ,^? escap+ gradually "w _! way upw>d ?r\gh ! air4 ,?is expla9s :y x is t our atmosph]e is n (t5 saturat$ ev5 ne> l>ge bodies ( wat]1 ! ret>d+ effect ( ! air ^u ! evaporation prev5t+ m ?an ! lay]s ( air ne> ! wat] surface becom+ saturat$4 ,j z ! am\nt ( salt t c be held 9 solution 9 a liquid is less5$ by cool+ ! solution 7,art4 #bf71 s ! am\nt ( wat] vapor t c be held 9 ! air is less5$ by l[]+ its temp]ature4 ,if air n moi/ en\gh to be saturat$ ) wat] vapor is cool$1 x w1 z ! cool+ cont9ues1 f9ally rea* a temp]ature at :i* x w be saturat$ or w conta9 all ! wat] vapor x c hold at ?is temp]ature4 ,if ! air be /ill fur!r cool$ "s ( ! wat] vapor w cond5se & may =m fog1 dew1 ra91 sn[1 etc41 ! =m x takes dep5d+ ^u :]e & h[ ! cool+ takes place4 #afh4 ,! ,=mation ( ,dew4--,if ! cool+ ( ! atmosph]e is at ! surface ( "s cold object :i* l[]s ! temp]ature ( ! air bel[ its saturation po9t1 "s ( its moi/ure cond5ses & collects ^u ! cold surface z dew4 ,?is may be notic$ ^u ! surface ( a pit*] ( ice-wat] 9 summ]4 ,at night1 ! temp]ature ( grass & o!r objects ne> or on ! gr\nd may fall mu* fa/] ?an t ( ! atmosph]e ow+ to ! radiation ( heat f ^! objects4 ,if ! temp]ature falls bel[ ! saturation po9t1 dew w be =m$4 ,?is natural radiation is h9d]$ :5 x is cl\dy1 !re=e little dew =ms on cl\dy nights4 ,cle> nights help radiation1 !re=e we h ! mo/ dew on nights :5 ! sky is cle>4 ,if ! temp]ature is bel[ freez+1 fro/ =ms in/ead ( dew4 #afi4 ,=mation ( ,fog4--,if ! cool+ at night is great en\gh to cool ! body ( air ne> ! e>? bel[ ! saturation temp]ature1 !n n only may dew be =m$1 b "s moi/ure is cond5s$ 9 ! air itself1 usually ^u f9e du/ p>ticles susp5d$ 9 x4 ,?is con/itutes a fog4 ,if ! cool+ ( ! body ( air takes place above ! e>?'s surface z :5 a w>m moi/ curr5t ( air ent]s a cold] region1 e4g41 moves ov] ! top ( a cold m\nta91 or into ! upp] air1 !n z ?is air is cool$ bel[ its saturation po9t1 cond5sation ^u f9e susp5d$ du/ p>ticles takes place1 & a cl\d is =m$4 ,if mu* moi/ure is pres5t 9 ! cl\d1 ! drops ( wat] gr[ 9 size until !y beg9 to fall & ra9 results2 or if x is cold en\gh1 in/ead ( ra91 sn[flakes w be =m$ & fall4 ,sometimes :irl+ w9ds 9 sev]e ?und]/orms c>ry ! ra9drops into cold] & !n w>m] regions1 alt]nately freez+ & moi/5+ ! drops or bits ( ice4 ,x is 9 ?is way t hail is said to be =m$4 #agj4 ,! ,dew ,po9t4--,! temp]ature to :i* air mu/ be cool$ to saturate x or ! temp]ature at :i* cond5sation beg9s is call$ ! dew po9t4 ,?is is (t5 det]m9$ 9 ! laboratory by p>tly fill+ a poli%$ metal vessel ) wat] & cool+ ! wat] by add+ ice until a ?9 film ( moi/ure is =m$ ^u ! out] surface4 ,! temp]ature ( ! surface :5 ! moi/ure fir/ =ms is ! dew po9t4 #aga4 ,! ,humidity ( ! ,atmosph]e4--,aft] ! dew po9t has be5 obta9$1 "o may compute ! relative humidity or degree ( saturation ( ! atmosph]e1 f ! table giv5 bel[4 ,?is is def9$ z ! ratio ( ! am\nt ( wat] vapor pres5t 9 ! air to ! am\nt t w\ld be pres5t if ! air 7 saturat$ at ! same temp]ature4 ,= example1 if ! dew po9t is #e;,c4 & ! temp]ature ( ! air is #bb;,c41 we f9d ! d5sities ( ! wat] vapor at ! two temp]atures1 & f9d _! ratio3 #f4h_/ai4c #ce p] c5t4 ne>ly4 ,det]m9ations ( humidity may give indication ( ra9 or fro/ & are regul>ly made at wea!r bureau /ations4 ,!y are also made 9 build+s su* z gre5h\ses1 hospitals1 & s*oolh\ses to see if ! air is moi/ en\gh4 ,= ! mo/ heal?ful conditions ! relative humidity %\ld be f #dj p] c5t4 to #ej p] c5t4 ,,weight ,,( ,,wat] 7w7 ,,9 ,,grams ,,conta9$ ,,9 #a ,,cubic ,,met] ,,( ,,saturat$ ,,air ,,at ,,v>i\s ,,temp]atures 7t7,c4 -------------- t,c4 w -------------- -#aj #b4a - #i #b4d - #h #b4g - #g #c4j - #f #c4b - #e #c4e - #d #c4h - #c #d4a - #b #d4d - #a #d4f #j #d4i #a #e4b #b #e4f #c #f4j #d #f4d #e #f4h #f #g4c #g #g4g #h #h4a #i #h4h #aj #i4d #aa #aj4j #ab #aj4f #ac #aa4c #ad #ab4j #ae #ab4h #af #ac4f #ag #ad4e #ah #ae4a #ai #af4b #bj #ag4b #ba #ah4b #bb #ai4c #bc #bj4d #bd #ba4e #be #bb4i #bf #bd4b #bg #be4f #bh #bg4j #bi #bh4f #cj #cj4a -------------- #agb4 ,wet & ,dry ,bulb ,hygromet]4--,a device = indicat+ ! relative humidity ( ! air is call$ an hygromet]4 ,!re are v>i\s =ms4 ,! wet & dry bulb hygromet] is %[n 9 ,fig4 #adi4 ,?is device consi/s ( two !rmomet]s1 "o ) its bulb dry & expos$ to ! air1 ! o!r bulb be+ kept cont9ually moi/ by a wick dipp+ into a vessel ( wat]4 ,an application ( ! pr9ciple ( cool+ by evaporation is made 9 ?is in/rum5t4 ,unless ! air is saturat$ s t evaporation is prev5t$1 ! wet-bulb !rmomet] %[s a l[] temp]ature1 ! diff]5ce dep5d+ ^u ! am\nt ( moi/ure 9 ! air1 or ^u ! relative humidity4 ,mo/ det]m9ations ( relative humidity are made ) ?is k9d ( in/rum5t4 ,x is necess>y 9 ord] to make an accurate det]m9ation1 to fan or set ! air 9 motion ab\t ! !rmomet]s = "s "t be=e read+ !m4 ,! relative humidity is !n f\nd by us+ tables giv+ ! relative humidity t corresponds to any read+ ( ! !rmomet]s4 ,illu/ration3 ,,fig4 #adi4--,wet & dry bulb hygromet]4 ,illu/ration3 ,,fig4 #aej4--;,a dial hygromet]4 ,a =m ( hygromet] 9 common use is %[n 9 ,fig4 #aej4 ,9 ?is device1 a ?9 /rip ( hygroscopic mat]ial 7z a piece ( goose quill7 is =m$ into a spiral coil4 ,"o end ( ?is is fa/5$ to a po/4 ,! o!r end c>ri$ a h& or po9t]4 ,! latt] moves ov] a pr9t$ scale & indicates directly ! relative humidity4 ,its indications %\ld be te/$ by comp>+ its read+s ) ! results ( dew-po9t det]m9ations4 ,! position ( ! po9t] may be adju/$ by turn+ ! po/4 ,important ,topics #a4 ,wat] vapor 9 ! air4 ,cause & effect4 #b4 ,=mation ( dew1 fog1 ra91 & sn[4 #c4 ,dew po9t1 relative humidity4 #d4 ,use ( ! dry- & wet-bulb hygromet]4 ,goose-quill hygromet]4 ,ex]cises #a4 ,h[ is ! relative humidity ( ! air affect$ by w>m+ x8 ,expla94 #b4 ,h[ does ! :ite cl\d ( /eam se5 ab\t a locomotive 9 cold wea!r diff] f fog8 ,expla94 #c4 ,9 cold wea!r is ! relative humidity ( air out ( doors & indoors ! same8 ,expla94 #d4 ,comp>e ! relative humidity ( air 9 a des]t & ne> ! ocean4 #e4 ,look up ! d]ivation ( ! t]m hygromet]4 ,give ! use ( ! in/rum5t4 #f4 ,f9d ! relative humidity ( air at #bj;,c4 if its dew po9t is at #aj;,c4 #g4 ,h[ may ! relative humidity ( ! air 9 a home be increas$8 #h4 ,:at is ! effect ( high humidity 9 ! summ] ^u human be+s8 ,h[ d y expla9 ?is8 #i4 ,does dew fall8 ,expla9 h[ dew is =m$8 #aj4 ,9 :at respects is a cl\d simil> to a fog8 ,9 :at respects diff]5t8 #aa4 ,:y are iceb]gs frequ5tly envelop$ 9 fog8 #ab4 ,does dew =m 9 ! day "t8 ,expla94 7#g7 ,,evaporation #agc4 ,effects ( ,evaporation4--,9 ,art4 #ai ! cool+ effect ( evaporation is m5tion$ & "s explanation is made ( ! cool+ effect obs]v$4 ,s9ce evaporation is employ$ 9 s _m ways1 & s9ce its action is simply expla9$ by ! /udy we h made ( molecul> motions & molecul> =ces1 x may be well to consid] ?is subject fur!r4 ,take ?ree %all[ di%es1 & place 9 "o a little wat]1 9 ano!r "s alcohol1 & "s e!r 9 ! ?ird1 ! liquids be+ tak5 f bottles t h /ood sev]al h\rs 9 ! room s t all are at ! same temp]ature4 ,aft] a %ort "t take ! temp]ature ( ! ?ree liquids4 ,ea* w be at a l[] temp]ature ?an at fir/1 b ( ! ?ree ! e!r w be f\nd to be ! coole/1 alcohol next1 & ! wat] ne>e/ its fir/ temp]ature4 ,x w be notic$ also t ! e!r has evaporat$ mo/ 9 ! same "t4 ,simil> effects may be obs]v$ by plac+ a few drops ( ea* ( ^! ?ree liquids ^u ! back ( "o's h&1 or by plac+ a few drops 9 turn ^u ! bulb ( a simple air !rmomet]4 #agd4 ,cool+ ,effect ( ,evaporation4--,! molecules t leave an evaporat+ liquid are naturally ! swifte/ mov+ ones1 t is1 ! ones hav+ ! highe/ temp]ature1 s _! escape leaves ! liquids cool] ?an be=e1 & ! "o ^: molecules leave fa/e/ is naturally ! "o t becomes colde/1 t is1 ! e!r1 9 ! exp]im5t ( ,art4 #agc4 ,if no air pressure 7 ex]t$ ^u ! surface ( ! liquid1 ! escape ( ! molecules w\ld be mu* increas$ & ! temp]ature ( ! liquid w\ld be l[]$ rapidly4 ,to te/ ?is1 fill a ?9 wat* glass ) e!r & place x ov] a ?9 slip ( glass ) a drop ( cold wat] betwe5 ! two4 ,n[ place ?is app>atus "u ! receiv] ( an air pump & exhau/ ! air4 ,! rapid evaporation ( ! e!r s l[]s its temp]ature1 t (t5 ! drop ( wat] is froz54 ,! l[e/ temp]atures are obta9$ by evaporat+ liquids at r$uc$ pressure4 ,onnes by evaporat+ liquid helium at a pressure ( ab\t #a4b mm4 rea*$ ! l[e/ temp]ature yet atta9$1 -#def;,f41 or -#bga4c;,c4 ,if f\r !rmomet]s are tak51 ! bulbs ( ?ree be+ wett$ respectively ) e!r1 alcohol1 & wat] ! f\r? be+ dry1 on vigor\sly fann+ ^!1 ! moi/5$ !rmomet]s %[ t !y h be5 cool$ :ile ! dry "o is unaffect$4 ,?is indicates t fann+ a dry body at ! temp]ature ( ! air does n *ange its temp]ature4 ,fann+ does increase evaporation by remov+ ! air conta9+ ! evaporat$ molecules ne> ! surface ( ! liquid s t unsaturat$ air is cont9ually ov] ! liquid4 ,if a p9t ( wat] is plac$ 9 a bottle & ano!r p9t 9 a wide pan ! latt] w become dry mu* soon] because ( ! great] surface ov] :i* evaporation c take place4 ,application ( ?is is made at salt works :]e ! br9e is spread out 9 %all[ pans4 #age4 ,rate ( ,evaporation4--,! rate ( evaporation is affect$ by sev]al factors4 ,^! h be5 illu/rat$ 9 ! prec$+ p>agraphs4 ,to briefly summ>ize3 ,! rate ( evaporation ( a liquid is affect$ by-- 7a7 ,! nature ( ! liquid4 7b7 ,! temp]ature ( ! liquid4 7c7 ,! pressure ^u its evaporat+ surface4 7d7 ,! degree ( saturation ( ! space into :i* ! liquid is evaporat+4 7e7 ,! rate ( circulation ( air ov] its surface4 7f7 ,! ext5t ( surface expos$ to evaporation4 #agf4 ,molecul> ,motion 9 ,solids4--,evid5ce ( molecul> motion 9 liquids is giv5 by expansion on heat+1 evaporation1 & diffusion4 ,d any ( ^! l9es ( evid5ce apply to solids8 ,x is a fact ( common exp]i5ce t solids d become l>g] on heat+4 ,spaces are left betwe5 ! ends ( rails on railroads s t :5 !y exp& 9 summ] !y w n di/ort ! track4 ,iron tires are plac$ on :eels by heat+ !m until !y slip on easily4 ,!n on cool+1 ! iron %r9ks & presses ! :eel tightly4 ,_m common demon/rations ( expansion are f\nd 9 lecture rooms4 ,! fact ( ! evaporation ( a solid is (t5 detect$ by notic+ ! odor ( a sub/ance4 ,! odor ( mo? balls is "o example4 ,camphor also evaporates4 ,heat$ t9 has a *>act]i/ic odor not$ by _m4 ,ice & sn[ disappe> 9 w9t] ev5 ?\gh ! temp]ature is bel[ freez+4 ,wet clo!s1 freeze dry1 t is1 dry aft] freez+1 by evaporation4 ,a few cry/als ( iod9e plac$ 9 a te/-tube & g5tly heat$ =m a vapor easily se51 ev5 ?\gh none ( ! iod9e melts4 ,:]e ! vapor /rikes ! side ( ! tube1 x cond5ses back to d>k gray cry/als ( iod9e4 ,?is *ange f solid directly to gas & back aga9 )\t becom+ liquid is call$ sublimation4 ,a numb] ( solids are purifi$ by ?is process4 ,important ,topics #a4 ,cool+ effect ( evaporation1 rate ( evaporation affect$ by six conditions4 #b4 ,effects ( molecul> motion 9 solids3 7a7 ,expansion1 7b7 ,evaporation1 7c7 ,sublimation4 ,ex]cises #a4 ,does spr9kl+ ! /reets or sidewalks cool ! air8 ,:y8 #b4 ,give an illu/ration = ea* ( ! factors affect+ evaporation4 #c4 ,give an illu/ration = ea* ( ! ?ree evid5ces ( molecul> motions 9 solids4 #d4 ,s9ce ?ree-qu>t]s ( ! e>?'s surface is cov]$ ) wat]1 :y is n ! air con/antly saturat$8 #e4 ,if ! air has ! temp]ature ( ! body1 w fann+ ! p]fectly dry face cool "o8 ,expla94 ,w ! effect be ! same if ! face is moi/8 ,expla94 #f4 ,:at is ! cause ( ,cl\d ,capp$ m\nta9s8 #g4 ,:y does ! exhau/ /eam f an eng9e appe> to h s mu* great] volume on a cold day 9 w9t] ?an on a w>m "o 9 summ]8 #h4 ,:at causes an unfroz5 pond or lake to /eam on a v cold day 9 w9t]1 or on a v cool morn+ 9 summ]8 #i4 ,z ! air on a m\nta9 top settles d[n ! sides to places ( great] pressure1 h[ w its temp]ature be affect$8 its relative humidity8 ,expla94 #aj4 ,on our ,pacific coa/1 moi/ w9ds bl[ f ! we/ ov] ! m\nta9s4 ,:]e w x ra98 ,:]e be dry8 ,expla94 ,,*apt] ,,viii ,,heat ,,& ,,"w 7#a7 ,,heat ,,measurem5t ,,& ,,specific ,,heat #agg4 ,specific ,heat4--,9 ! /udy ( d5sity & specific gravity x is made cle> t diff]5t sub/ances diff] widely 9 ! am\nt ( matt] conta9$ 9 equal volumes1 e4g41 lead is mu* d5s] ?an wat]4 ,! /udy ( ! relative d5sities ( sub/ance is usually consid]$ "u ! subject ( specific gravity4 ,specific heat z di/+ui%$ f specific gravity is conc]n$ ) ! capacity = heat possess$ by diff]5t sub/ances4 ,! def9ition = specific heat is3 ,! ratio ( ! am\nt ( heat requir$ to *ange ! temp]ature ( a giv5 mass ( a sub/ance #a ,c4 degree to ! am\nt ( heat requir$ to *ange ! temp]ature ( ! same mass ( wat] #a ,c4 degree4 ,by def9ition1 x requires #a calorie to raise ! temp]ature ( ! gram ( wat] #a;,c4 ,! specific heat !re=e ( wat] is tak5 z "o4 ,! specific heat ( mo/ sub/ances except hydrog51 is less ?an t ( wat]1 & z a rule1 ! d5s] ! body ! less its specific heat1 z may be obs]v$ 9 ! foll[+ table3 ----------------------------- ,specific ,specific gravity heat ----------------------------- ,gold #ai4c #j4jcb ,m]cury #ac4f #j4jcc ,copp] #h4i #j4jic ,brass #h4d-h4i #j4jid ,nickel #h4eg #j4aa ,iron #g4e #j4aabe ,alum9um #b4fg #j4bah ,glass #b4e-c4f #j4ai ,ice #j4iah #j4ejd ,air #j4jjabi #j4bcg ,/eam #j4jjjfa #j4dhj ,hydrog5 #j4jjjji #c4dji ----------------------------- #agh4 ,me?od ( ,det]m9+ ,specific ,heat4--,! specific heat ( a body is usually det]m9$ by :at is call$ ! me?od ( mixtures4 ,= example1 a def9ite weight ( a sub/ance1 say a #bjj-;g4 iron ball1 is plac$ 9 boil+ wat] until x has ! temp]ature ( ! hot wat]1 #ajj;,c4 ,suppose t #cjj g4 ( wat] at #ah;,c4 be plac$ 9 a calorimet]1 & t ! hot iron ball on be+ plac$ 9 ! wat] raises its temp]ature to #bc4e;,c4 ,! heat receiv$ by ! wat] equals #e4e #cjj #afej calories4 ,?is mu/ h come f ! heat$ iron ball4 #bjj g4 ( iron !n 9 cool+ #gf4e;,c4 7#ajj-bc4e7 gave out #afej calories4 ,!n #a g4 ( iron 9 cool+ #gf4e;,c4 ,w\ld give out #h4be calories or #a g4 ( iron cool+ #a;,c4 w\ld yield ab\t #j4aa calorie4 ,! specific heat ( ! iron is !n #j4aa4 ,= accurate det]m9ation ! heat receiv$ by ! calorimet] mu/ be consid]$4 #agi4 ,heat ,capacity ( ,wat]4--,! l>ge capacity = heat %[n by wat] is useful 9 regulat+ ! temp]ature ( ! air ne> lakes & ! ocean4 ,9 hot wea!r ! wat] rises sl[ly 9 temp]ature absorb+ heat f ! w>m w9ds bl[+ ov] x4 ,9 w9t] ! l>ge am\nt ( heat /or$ 9 ! wat] is sl[ly giv5 out to ! air above4 ,?us ! climate ne> ! ocean is made m mod]ate bo? 9 w9t] & summ] by ! l>ge capacity ( wat] = heat4 ,?is l>ge heat capacity ( wat] may seem to be a disadvantage :5 "o is w>m+ x = dome/ic purposes s9ce x requires s mu* heat to w>m wat] to boil+4 ,h[ev]1 x is ?is capacity t makes hot-wat] bottles & hot-wat] heat+ effective4 ,if "o takes a p\nd ( ice at #j;,c4 9 "o di% & a p\nd ( wat] at #j;,c4 9 ano!r1 & w>ms ! di% ( ice by a ,buns5 flame until ! ice is j melt$1 & !n w>ms ! wat] 9 ! o!r di% = ! same "t1 ! wat] w be f\nd to be hot & at a temp]ature #hj;,c41 or #agf;,f4 #ahj4 ,! ,heat ( ,fusion ( ,ice4--,?is exp]im5t indicates ! l>ge am\nt ( heat requir$ to *ange ! ice to wat] )\t *ang+ its temp]ature4 ,z indicat$ by ! exp]im5t1 x requires #hj calories to melt #a g4 ( ice )\t *ang+ its temp]ature or1 9 o!r words1 if "o plac$ #a g4 ( ice at #j;,c4 9 #a g4 ( wat] at #hj;,c41 ! ice w\ld be melt$ & ! wat] w\ld be cool$ to #j;,c4 #aha4 ,heat ,giv5 out by ,freez+ wat]4--,j z #hj calories ( heat are requir$ to melt #a g4 ( ice1 s 9 freez+ #a g4 ( wat]1 #hj calories ( heat are giv5 out4 ,! fact t heat is set free or giv5 out :5 a liquid solidifies may be /rik+ly %[n by mak+ a /rong solution ( sodium acetate4 ,on all[+ ?is to cool quietly x w come to ! room temp]ature & rema9 liquid4 ,if n[ a small cry/al ( sodium acetate is dropp$ into ! liquid ! latt] quickly becomes a solid mass ( cry/als1 at ! same "t ris+ m>k$ly 9 temp]ature4 ,! am\nt ( heat n[ lib]at$ mu/ ent] ! sodium acetate :5 ! mass ( cry/als is melt$ aga94 ,! l>ge am\nt ( heat t mu/ be lib]at$ be=e wat] freezes acc\nts = ! sl[ness ( ! =mation ( ice4 ,x is also ! reason :y ! temp]ature nev] falls s l[ 9 ! vic9ity ( l>ge lakes z x does f> inl&1 ! heat giv5 out by ! freez+ wat] w>m+ ! surr\nd+ air4 ,! heat t disappe>s on melt+ & reappe>s on solidify+ is call$ ! heat ( fusion4 ,x is sometimes call$ lat5t heat s9ce ! heat seems to become hidd5 or lat5t4 ,x is n[ believ$ t ! heat en]gy t disappe>s :5 a body melts has be5 trans=m$ into ! pot5tial en]gy ( p>tially sep>at$ molecules4 ,! heat ( fusion !re=e repres5ts ! "w done 9 *ang+ a solid to a liquid )\t a *ange ( temp]ature4 #ahb4 ,melt+ ( ,cry/all9e & ,amorph\s ,sub/ances4--,if a piece ( ice is plac$ 9 boil+ hot wat] & !n remov$1 ! temp]ature ( ! unmelt$ ice is /ill #j;,c4 ,!re is no kn[n means ( w>m+ ice "u atmosph]ic pressure above its melt+ po9t & ma9ta9+ its solid /ate4 ,ice be+ compos$ ( ice cry/als is call$ a cry/all9e body4 ,all cry/all9e sub/ances h fix$ melt+ po9ts4 ,= example1 ice always melts at #j;,c4 ,! melt+ po9ts ( "s common cry/all9e sub/ances are giv5 bel[3 ,melt+ ,po9ts ( ,"s ,cry/all9e ,sub/ances #a4 ,alum9um #feh ,c4 #b4 ,ca/ iron #abjj ,c4 #c4 ,copp] #ajhc ,c4 #d4 ,ice #j ,c4 #e4 ,lead #cbg ,c4 #f4 ,m]cury -#ci ,c4 #g4 ,ph5ol 7c>bolic acid7 #dc ,c4 #h4 ,plat9um #agee ,c4 #i4 ,salt 7sodium *loride7 #gie ,c4 #aj4 ,saltpet] 7potassium nitrate7 #cdj ,c4 #aa4 ,silv] #ifa ,c4 #ab4 ,sodium hyposulphite 7hypo7 #dg ,c4 #ac4 ,z9c #dai ,c4 ,non-cry/all9e or amorph\s sub/ances su* z glass1 t>1 glue1 etc41 d n h well def9$ melt+ po9ts z d cry/all9e bodies4 ,:5 heat$ !y gradually s(t5 & become fluid4 ,= ?is reason glass c be press$ & mold$4 #ahc4 ,*ange ( ,volume ,dur+ ,solidification4--,! fact t ice floats & t x breaks bottles & pipes 9 :i* x freezes %[s t wat] exp&s on freez+4 ,h[ a sub/ance may occupy m space :5 solid ?an :5 liquid may be und]/ood :5 we le>n t ice consi/s ( masses ( />-%ap$ cry/als4 7,see ,fig4 #aea47 ,! =mation ( ^! cry/als mu/ leave unoccupi$ spaces betwe5 !m 9 ! ice4 ,:5 liquefi$1 h[ev]1 no spaces are left & ! sub/ance occupies less volume4 ,mo/ sub/ances contract ^u solidify+4 ,antimony & bismu?1 h[ev]1 exp& on solidify+ :ile iron *anges little 9 volume4 ,only ^? bodies t exp&1 or else %[ little *ange ( volume on solidify+1 c make %>p ca/+s1 = if !y contract !y w n completely fill ! mold4 ,= ?is reason gold & silv] co9s mu/ be /amp$ & n ca/4 ,type metal1 an alloy ( antimony & lead1 exp&s on solidify+ to =m ! %>p outl9es ( good type4 ,sev]al important effects ( ! expansion ( wat] :5 freez+ %\ld be not$4 7a7 ,ice floats1 7b7 if x sank z soon z =m$1 lakes & riv]s w\ld freeze solid1 7c7 freez+ wat] is "o ( ! active ag5ts 9 ! dis9tegration ( rocks4 ,illu/ration3 ,,fig4 #aea4--;,ice cry/als4 ,illu/ration3 ,,fig4 #aeb4--,melt+ ice by pressure4 ,s9ce wat] exp&s on freez+1 pressure w\ld on compress+ ice at #j;,c41 t5d to turn x into wat]4 ,pressure does l[] ! melt+ po9t ( ice1 s t a little ice may melt :5 x is subject$ to pressure4 ,on remov+ ! pressure ! wat] freezes4 ,?is may be %[n by plac+ a loop ( f9e piano wire 7see ,fig4 #aeb7 ov] a piece ( ice support$ s t a weight may be hung ^u ! wire4 ,! wire w be f\nd to gradually cut ?r\gh ! ice1 ! melt$ ice refreez+ above ! wire4 ,important ,topics #a4 ,specific heat4 #b4 ,heat ( fusion ( ice4 #c4 ,cry/all9e sub/ances h fix$ melt+ po9ts4 #d4 ,expansion on freez+1 importance4 ,ex]cises #a4 ,:at are two advantages 9 ! high heat ( fusion ( ice8 #b4 ,:at are two advantages 9 ! expansion ( wat] :ile freez+8 #c4 ,h[ mu* heat w be requir$ to melt #ajjj g4 ( ice & w>m ! wat] to #bj;,c48 #d4 ,h[ _m grams ( ice at #j;,c4 c be melt$ by #djj g4 ( wat] at #ee;,c48 #e4 ,:at are two advantages ( ! high specific heat ( wat]8 ,two disadvantages8 #f4 ,if ! specific heat ( iron is #j4aabe1 h[ mu* ice at #j;,c4 c be melt$ by a #bjj-;g4 ball ( iron heat$ to #cjj;,c8 #g4 ,:at is ! temp]ature ( a hot ball ( iron weigh+ #hj g41 if :5 plac$ on a piece ( ice at #j;,c4 x melts #ij g4 ( ice8 #h4 ,if #ejj g4 ( copp] at #djj;,c4 are plac$ into #cjjj g4 ( wat] at #aj;,c4 :at w be ! result+ temp]ature8 #i4 ,:at weight ( wat] at #ij;,c4 w j melt #aj kg4 ( ice at #j;,c48 #aj4 ,if ! smoo? dry surface ( two pieces ( ice are press$ toge!r = a %ort "t ! two pieces w be froz5 into "o piece4 ,expla94 #aa4 ,tubs ( hot wat] are sometimes plac$ 9 vegetable cell>s to prev5t ! vegetables f freez+4 ,expla94 #ab4 ,h[ _m ,b4t4u4 are giv5 out :5 #b lbs4 ( wat] freeze8 7#b7 ,,heat ,,& ,,*ange ,,( ,,/ate ,illu/ration3 ,,fig4 #aec4--,! black cube 9 ! upp] corn] repres5ts "o cubic in* ( wat]4 ,! entire cube repres5ts ! space occupi$ by ! cubic in* ( wat] 9 ! =m ( /eam4 ,! r$uc$ spaces at ! bottom & sides %[ h[ mu* %ort ! cube is ( be+ "o cubic foot4 7,am]ican ,radiator ,co47 #ahd4 ,heat ( ,vaporization4--,9 our /udy ( evaporation 9 ,art4 #agd we consid]$ ! m rapidly mov+ or vibrat+ molecules 9 ! liquid escap+ to ! air above & ! sl[] mov+ molecules be+ left beh9d 9 ! liquid2 ?is means t a loss ( heat w result ^u evaporation1 ! liquid rema9+ becom+ cool] z ! process cont9ues4 ,n[ j z a ball ?r[n up 9 ! air loses its k9etic en]gy z x rises1 & acquires en]gy ( position or pot5tial en]gy1 s molecules escap+ f a liquid lose a c]ta9 am\nt ( k9etic en]gy or heat & acquire a correspond+ am\nt ( en]gy ( position or pot5tial en]gy4 ,conv]sely1 z ! ball returns to ! gr\nd its pot5tial en]gy is *ang$ to k9etic en]gy4 ,simil>ly :5 vapor molecules return to ! liquid condition !y lose _! en]gy ( position & acquire k9etic en]gy4 ,9 o!r words1 :5 a liquid evaporates a c]ta9 am\nt ( heat disappe>s1 or becomes lat5t & :5 ! vapor cond5ses ! heat reappe>s1 or becomes s5sible heat4 ,! am\nt ( heat t disappe>s :5 #a g4 ( a sub/ance is vaporiz$ is call$ ! heat ( vaporization4 ,9 ! case ( wat] at its boil+ po9t1 #ecf calories ( heat disappe> :5 #a g4 ( wat] turns to vapor1 & ?is same am\nt ( heat reappe>s :5 ! vapor cond5ses4 ,! *ange ( volume ( wat] on turn+ to /eam is %[n 9 ,fig4 #aec4 ,illu/ration3 ,,fig4 #aed4--;,effect ( pressure on ! boil+ po9t4 #ahe4 ,! ,boil+ ,po9t4--,! boil+ temp]ature dep5ds ^u ! pressure4 ,! boil+ po9t may be def9$ z ! temp]ature at :i* bubbles ( vapor are =m$ )9 ! liquid4 ,^! bubbles increase ! surface at :i* evaporation c take place 9 ! liquid1 & ! pr9cipal reason :y rapid application ( heat to a liquid does n raise its temp]ature above ! boil+ po9t is t z m heat is appli$ m bubbles =m s t ! increase ( evaporat+ surface supplies a correspond+ly great] surface = cool+4 ,! v>iation ( ! boil+ temp]ature ) *ang+ pressure may be %[n by p>tly fill+ a /rong #g_/h-;94 te/-tube ) wat]4 ,close ! neck ) a "o-hole rubb] /opp] ?r\gh :i* passes a glass tube to :i* is atta*$ a s(t rubb] tube4 7,see ,fig4 #aed47 ,support ! tube by a hold]1 heat ! wat] & boil until all ! air is driv5 f ! tube1 !n close ! s(t rubb] tube ) a p9* cock & hold ! tube 9 an inv]t$ position4 ,on cool+ ! end ( ! tube above ! wat] ) cold wat] or sn[1 ! vapor )9 is cond5s$ & ! pressure ^u ! wat] is r$uc$4 ,vigor\s boil+ beg9s at once4 ,by cond5s+ ! vapor repeat$ly ! wat] may be made to boil at ! room temp]ature4 ,at ! top ( ,mt4 ,blanc wat] boils at #hd;,c4 ,:ile 9 /eam boil]s at #bbe lbs4 pressure to ! squ>e in* ! boil+ po9t is ne>ly #bjj;,c4 #ahf4 ,laws ( ,boil+4--,! foll[+ /atem5ts h be5 f\nd by exp]im5ts to be true4 #a4 ,e liquid has its own boil+ po9t :i* "u ! same conditions ( pressure is always ! same4 #b4 ,! temp]ature ( ! boil+ liquid rema9s at ! boil+ po9t until all ! liquid is *ang$ into vapor4 #c4 ,! boil+ po9t rises ) increas$ pressure & falls if ! pressure is dim9i%$4 #d4 ,a boil+ liquid & ! vapor =m$ f x h ! same temp]ature4 ,on cool+1 a vapor w liquefy at ! boil+ po9t4 ,illu/ration3 ,,fig4 #aee4--;,di/ill+ app>atus4 #e4 ,! solution ( solid sub/ances 9 a liquid raises its boil+ po9t1 additional en]gy be+ ne$$ to ov]come ! adhesion involv$ 9 ! solution4 ,! boil+ po9t is also affect$ by ! "* ( ! vessel conta9+ ! liquid4 ,9 glass ! boil+ po9t is #aja4 ,illu/ration3 ,,fig4 #aef4--;,a vacuum pan4 #ahg4 ,di/illation ( ,wat]4--,usually :5 solids are dissolv$ 9 liquids ! vapor com+ f ! liquid conta9s none ( ! dissolv$ solid4 ,?us by evaporat+ salt sea wat]1 & collect+ & cond5s+ ! vapor1 pure wat] is obta9$4 ,di/illation is ! process ( boil+ a liquid & cond5s+ ! vapor =m$ back aga9 into a liquid4 7,see ,fig4 #aee47 ,! liquid to be di/ill$ is plac$ 9 vessel ,f & boil$4 ,! vapor is conduct$ into ! tube ,j :i* is surr\nd$ by a l>g] tube conta9+ cold wat]4 ,! vapor is cond5s$ on ! cold walls ( ! tube4 ,! result+ liquid is collect$ 9 ! vessel ,r4 ,di/illation is employ$ = two purposes3 7a7 ,to remove impurities f a liquid 7wat] is purifi$ 9 ?is way74 7b7 ,mixtures ( diff]5t liquids hav+ diff]5t boil+ po9ts may be sep>at$ by di/illation4 ,! "o hav+ ! l[] boil+ po9t w be vaporiz$ fir/4 ,?us a mixture ( alcohol & wat]1 on di/illation yields a di/illate hav+ a mu* l>g] p]c5tage ( alcohol ?an at fir/4 ,repeat+ ?is process :i* is call$ fractional di/illation yields alcohol ( increas+ /r5g? ( purity4 ,di/ill$ liquor su* z alcohol1 br&y1 & :isky are made by di/ill+ f]m5t$ liquor1 alcohol be+ made f f]m5t$ gra9s4 ,gasol9e & k]os5e are di/ill$ f crude petroleum4 ,sometimes z 9 ! production ( sug> or evaporat$ milk ! object is to remove ! wat] by evaporation 9 ord] to obta9 ! solid mat]ial4 ,s9ce ! two sub/ances nam$ are injur$ by heat+1 ! syrup1 or milk is evaporat$ "u r$uc$ pressure 9 a vacuum pan1 t is 9 a boil] f :i* air & vapor are remov$ by an air pump4 7,see ,fig4 #aef47 #ahh4 ,artificial ,cool+4--,! fact has be5 br\ght out t :5 a solid is melt$1 a c]ta9 am\nt ( heat1 call$ ! heat ( fusion1 is absorb$ or disappe>s4 ,?is absorption ( heat is also notic$ :5 a solid is liquefi$ by dissolv+ x 9 a liquid z well z :5 x is liquefi$ by simply apply+ heat4 ,?us if "s table salt is plac$ 9 a tumbl] ( wat] ! temp]ature ( ! solution is l[]$ sev]al degrees bel[ t ( ! salt & wat] us$4 ,! liquefaction or solution ( ! salt has be5 accompani$ by an absorption or disappe>ance ( heat4 ,?is heat has be5 tak5 f ! salt & f ! wat]1 result+ 9 a l[]$ temp]ature4 ,sal ammoniac or ammonium nitrate :5 dissolv$ 9 wat] produce a mu* m m>k$ cool+ effect ?an does table salt4 ,! dissolv+ ( a cry/al 9 a liquid is some?+ l evaporation1 except t ! molecules ( ! liquid attract ! molecules ( ! solid & ?us assi/ ! *ange ( /ate4 #ahi4 ,freez+ ,mixtures4--,if "o attempts to freeze a solution ( salt & wat]1 ice w n =m at #j;,c4 b sev]al degrees l[]4 ,! ice =m$ h[ev] is pure4 ,evid5tly ! attraction ( ! molecules ( salt = ! wat] molecules prev5t$ ! =mation ( ice until ! motions ( ! wat] molecules _h be5 r$uc$ m ?an is necess>y 9 pure wat]4 ,z ! temp]ature ( freez+ wat] is t ( melt+ ice1 ice 9 a salt solution melts at l[] temp]ature ?an 9 pure wat]4 ,9 a saturat$ salt solution ?is temp]ature is -#bb;,c4 ,x is = ?is reason t ! mixture ( ice & salt us$ 9 freez+ cream is s effective1 ! salt wat] 9 melt+ ! ice1 be+ cool$ to a temp]ature _m degrees bel[ ! freez+ po9t ( ! cream4 ,! be/ proportion = a freez+ mixture ( salt & ice is "o "p salt to ?ree p>ts ( f9ely p[d]$ or %av$ ice4 #aij4 ,refrig]ation by ,evaporation4--,int5se cold is also produc$ by p]mitt+ ! rapid evaporation ( liquids "u pressure4 ,c>bon dioxide "u high pressure is a liquid1 b :5 all[$ to escape into ! air evaporates s rapidly t a portion ( ! liquid is froz5 into solid c>bon dioxide :i* has a temp]ature ( -#hj ,c4 ,! evaporation ( liquid ammonia by p]mitt+ x to escape into a pipe1 "u r$uc$ pressure1 is us$ on a l>ge scale z a means ( produc+ cold 9 cold /orage & refrig]ation plants4 7,see ,fig4 #aeg47 ,illu/ration3 ,,fig4 #aeg4--;,diagram ( a refrig]at+ sy/em4 ,! ess5tial p>ts ( ! refrig]at+ sy/em employ+ ammonia is repres5t$ 9 ,fig4 #aeg4 ,! compressor exhau/s ammonia gas f ! coil$ pipe 9 ,e & compresses ! gas 9 ,c1 :]e "u #aej p\nds pressure & ! cool+ effect ( wat] x cond5ses to liquid ammonia4 ,?is is all[$ to pass sl[ly ?r\gh ! regulat+ valve1 :]eupon x evaporates & exp&s 9 ! long coil$ pipe 9 ,e on its way back to ! compressor4 ,?is evaporation & expansion causes a l>ge am\nt ( heat to be absorb$ f ! br9e1 cool+ ! latt] bel[ ! freez+ po9t ( pure wat] & ?us p]mitt+ ! freez+ ( cans ( wat] susp5d$ 9 ! br9e4 ,! *ill$ br9e may also be s5t ?r\gh pipes 9 ord] to cool /orage rooms conta9+ meat or o!r food products4 ,! ammonia absorbs heat :5 x vaporizes & gives up heat :5 x is compress$ & liquifi$4 ,important ,topics #a4 ,heat ( vaporization1 ( wat] #ecf calories p] gram4 #b4 ,boil+ po9t1 effect ( pressure ^u boil+ po9t1 laws ( boil+4 #c4 ,di/illation1 artificial cool+1 freez+ mixtures1 refrig]ation by evaporation4 ,ex]cises #a4 ,h[ mu* heat is requir$ 7a7 to melt #a g4 ( ice at #j;,c41 7b7 to raise ! temp]ature ( ! wat] result+ to #ajj;,c41 7c7 to *ange ?is wat] to /eam8 #b4 ,if ! wat] leav+ a /eam radiator is z hot z ! /eam h[ is ! room w>m$8 #c4 ,:at is ! effect ( plac+ salt ^u icy sidewalks 9 cold wea!r8 #d4 ,is ra9 wat] di/ill$ wat]8 ,is x p]fectly pure8 #e4 ,:at are two advantages ( ! high heat ( vaporization ( wat]8 #f4 ,if ! heat f #a g4 ( /eam at #ajj;,c4 9 *ang+ to wat] & cool+ to #j;,c4 c\ld be us$ 9 melt+ ice at #j;,c4 h[ mu* ice w\ld be melt$8 7#c7 ,,heat ,,& ,,"w #aia4 ,necessity = ,heat ,en]gy4--,f e>ly times man has be5 able to trans=m motion into heat1 & has us$ ?is ability 9 _m directions z 9 />t+ fires & w>m+ himself by friction4 ,x took man _m c5turies1 h[ev]1 to devise an effective ma*9e = trans=m+ heat into me*anical en]gy or to use x 9 do+ "w4 ,! p[] ( a man is small & z long z ! "w ( ! _w _h to be done by man p[]1 progress 0 ret>d$4 ,:5 man began ! use ( bea/s ( burd51 he took a long /ep 9 advance s9ce "o man c\ld !n employ & direct ! p[] ( _m m5 9 ! animals he controll$4 ,man also built wat]-:eels & w9dmills ?us ga9+ p[] directly f ! =ces ( nature & ^! add$ mu* to 8 work+ ability4 ,b he took ! greate/ /ep 9 ga9+ control ov] 8 surr\nd+s :5 he le>n$ to use heat en]gy & to make x drive 8 ma*9es4 #aib4 ,heat ,eng9es4--,at ! pres5t "t !re is a great v>iety ( heat eng9es 9 use su* z /eam1 hot air1 gas1 & gasol9e eng9es1 all us+ heat en]gy to produce motion4 ,! expansive p[] ( /eam :5 conf9$ has be5 obs]v$ = hundr$s ( ye>s & _m diff]5t ma*9es h be5 inv5t$ to use x 9 do+ "w4 ,illu/ration3 ,,fig4 #aeh4--;,cross-section view ( cyl9d] & /eam *e/ ( a /eam eng9e4 ,illu/ration3 ,,fig4 #aei4--,! /eam drives ! pi/on to ! left4 ,illu/ration3 ,,fig4 #afj4--;,ext]nal view ( /eam eng9e4 #aic4 ,! ,/eam-eng9e4--,! man :o p]fect$ ! /eam-eng9e1 & devis$ its mod]n =m 0 ,james ,watt 7#agcf-ahai74 ,! ess5tial p>ts & ! action ( ! /eam eng9e may be readily und]/ood by /udy+ a diagram4 ,9 ,fig4 #aeh1 ,s /&s = /eam *e/1 ,c = cyl9d]1 ,p = pi/on & v = slide valve4 ,! fir/ two are holl[ iron boxes1 ! latt] are p>ts t slide back & =? )9 !m4 ,! action ( ! /eam eng9e is z foll[s3 ,/eam "u pressure ent]s ! /eam *e/1 passes into ! cyl9d] & pu%es ! pi/on to ! o!r end4 ,! slide valve is mov$ to its position 9 ,fig4 #aei4 ,/eam n[ ent]s ! "r end ( ! cyl9d]1 driv+ ! pi/on to ! left1 ! dead /eam 9 ! left end ( ! cyl9d] escap+ at ,e to ! air4 ,! slide valve is n[ %ift$ to its fir/ position & ! process is repeat$4 ,x w assi/ ! /ud5t to und]/& ?is action if he makes a c>dbo>d model ( ^! p>ts1 ! pi/on & slide valve be+ movable4 ,9 practical /eam-eng9es1 ! pi/on rod is atta*$ to a crank rod fa/5$ to a crank :i* turns a :eel4 7,see ,fig4 #afj47 ,! back & =?1 or reciprocat+ motion ( ! pi/on is by ?is means trans=m$ into rot>y motion1 j z 9 ! sew+-ma*9e ! back-&-=? motion ( ! treadle produces rot>y motion ( ! l>ge :eel4 ,^u ! %aft ( ! /eam eng9e is fa/5$ an ecc5tric 7see ,fig4 #afc7 :i* moves ! slide valve4 ,! /eam eng9e acts cont9u\sly z long z /eam is suppli$ to x4 ,s9ce x %ifts ! position ( ! slide valve automatically1 x is call$ an automatic /eam eng9e4 ,& because ! team drives ! pi/on bo? ways1 x is call$ a d\ble-act+ /eam eng9e4 ,see ,fig4 #afa = a l5g?-section ( a mod]n locomotive4 ,illu/ration3 ,,fig4 #afa4--,l5g?-section ( mod]n1 fa/-pass5g] locomotive4 ,a1 cyl9d] valve--pi/on type valve2 ,b1 cyl9d]--pi/on at out end ( /roke2 ,c1 boil] tubes--flues f fire-box2 ,d1 fire-tube type sup]heat]2 ,e1 draught scre52 ,f-,a1 fire-brick ar* to protect tubes f direct heat2 ,f-,b1 firebox2 ,g1 grate2 ,h1 exhau/ nozzle2 ,i1 safety valve ne/2 ,t1 ?rottle lev]2 ,r1 ?rottle rod2 ,y1 ?rottle valve4 #aid4 ,! ,me*anical ,equival5t ( ,heat4--,:ile wat*+ workm5 bore holes 9 cannon1 ,c\nt ,rum=d1 #agec-ahad1 notic$ ) mu* int]e/ ! l>ge am\nt ( heat produc$ 9 ! process4 ,he obs]v$ t ! heat develop$ seem$ to h "s relation to ! "w done ^u ! drill 9 bor+ ! holes4 ,lat] exp]im5ts p]=m$ by _m m5 indicat$ t a def9ite relation exi/s betwe5 ! heat produc$ by friction & ! am\nt ( "w done 9 ov]com+ ! friction4 ,?is discov]y indicates t 9 "s way heat is relat$ to en]gy & t heat is probably a =m ( en]gy4 ,lat] exp]im5ts h confirm$ ?is idea1 & x is n[ consid]$ well e/abli%$ t heat is a =m ( en]gy4 ,_m attempts h be5 made to discov] ! relation betwe5 ! units ( heat en]gy & ! units ( me*anical en]gy4 ,to illu/rate "o me?od employ$1 suppose "o measures a giv5 l5g? 9 in*es & 9 c5timet]s2 on divid+ "o result by ! o!r1 x w be f\nd t a c]ta9 relation exi/s betwe5 ! two sets ( measurem5ts1 & t 9 e case t #a 94 equals #b4ed cm4 ,simil>ly1 :5 ! same am\nt ( en]gy is measur$ bo? 9 heat units & 9 "w units a con/ant relation is always f\nd betwe5 ! units employ$4 ,"o ,b4,t4,u4 is f\nd equival5t to #ggh ft4-lbs4 #a calorie be+ equival5t to #db1gjj g4 cm4 7#dbg g4 m474 ,?is relation is call$ ! me*anical equival5t ( heat1 or 9 o!r words x repres5ts ! numb] ( "w units equival5t to "o heat unit4 ,illu/ration3 ,,fig4 #afb4--;,app>atus = det]m9+ ! me*anical equival5t ( heat4 ,illu/ration3 ,william ,gilb]t 7#aedj-afjc71 ,fa!r ( magnetic philosophy4 ,especially not$ = 8 exp]im5ts & discov]ies 9 magnetism2 fir/ to use ! ^w electricity4 ,fir/ man to practically emphasize exp]im5tal sci5ce4 ,,dr4 ,,william ,,gilb]t 7,popul> ,sci5ce ,mon?ly7 ,illu/ration3 ,james ,prescott ,j\le 7#ahah-ahhi71 ,engl&1 det]m9$ ! me*anical equival5t ( heat2 discov]$ ! relation betwe5 an electric curr5t & ! heat produc$2 fir/ prov$ exp]im5tally ! id5tity ( v>i\s =ms ( en]gy4 ,,james ,,prescott ,,j\le 7,popul> ,sci5ce ,mon?ly7 ,"o ( ! fir/ successful exp]im5ts 9 det]m9+ ! relation betwe5 "w units & heat units 0 devis$ by ,j\le 9 ,engl&4 7,see portrait p4 #bag47 ,! exp]im5t consi/$ 9 tak+ a c ( metal conta9+ wat] 7,fig4 #afb7 9 :i* 0 plac$ a !rmomet]1 & a rod c>ry+ paddles4 ,! rod 0 turn$ by a cord connect$ ?r\gh suitable app>atus to heavy weights1 ,w & ,w4 ,! en]gy repres5t$ by ! d[nw>d motion ( ! weights ?r\gh a giv5 di/ance 0 comp>$ ) ! heat en]gy develop$ 9 ! wat] z %[n by its rise 9 temp]ature4 ,c>eful exp]im5ts %[$ t :5 #ggh ft4-lbs4 ( "w _h be5 done by ! mov+ weights ! heat produc$ at ! same "t w\ld w>m "o p\nd ( wat] #a ,fahr5heit degree4 ,if ! exp]im5t 0 p]=m$ us+ metric units1 x 0 f\nd t ! exp5diture ( #db1gjj gram c5timet]s 7#dbg gram met]s7 w\ld result 9 produc+ en\gh heat to w>m "o gram ( wat] "o c5tigrade degree4 ,! facts j giv5 may be summ>iz$ z foll[s3 #ggh foot-p\nds ( en]gy are equival5t to #a ,briti% !rmal unit & #db1gjj gram c5timet]s1 or #dbg gram met]s1 ( en]gy are equival5t to #a calorie4 ,?is relation ( "w units to heat units is call$ ! me*anical equival5t ( heat4 #aie4 ,! ,heat ,equival5t ( ,fuels & ,effici5cy ,te/s ( ,eng9es4--,to det]m9e ! effici5cy ( a /eam eng9e x is necess>y to "k n only ! me*anical equival5t ( heat b also ! heat produc$ by burn+ coal or gas2 #a lb4 ( av]age s(t coal %\ld produce ab\t #ab1fjj ,b4t4u4 ,n[ s9ce #ggh ft4-lbs4 are equival5t to "o ,b4t4u4 ! en]gy produc$ :5 #b lbs4 ( av]age s(t coal is burn$ is #ggh #ab1fjj #b #ai1fje1fjj ft4-lbs4 ,9 actual practice #b lbs4 ( av]age s(t coal burn$ w develop ab\t #a horse-p[] = #a h\r4 #a horse-p[]-h\r #cc1jjj ft4-lbs4 #fj #a1ihj1jjj ft4-lbs4 ,n[ effici5cy equals 7"w out7_/7"w 97 #a1ihj1jjj_/ai1fje1fjj #a_/aj or #aj p] c5t44 ,?is is ! effici5cy ( a good /eam eng9e4 ,ord9>y ones require #c lbs4 ( coal burn$ to ea* horse-p[]-h\r produc$ or !y are b #b_/c z effici5t or h b ab\t #g p] c5t4 effici5cy4 ,,heat ,,( ,,combu/ion ,,( ,,v>i\s ,,fuels ,data 9 ?is table are tak5 f ,u4 ,s4 ,geological ,survey1 ,bullet9 ,no4 #ccb1 & ,u4 ,s4 ,bureau ( ,m9es1 ,bullet9 ,no4 #bc4 ---------------------------------------- ----- ,b4,t4,u4 ,calories p] lb4 p] gram ---------------------------------------- ----- ,alcohol1 d5atur$ #aa1fjj #f1dej ,coal1 an?racite1 av]age #ab1fjj #g1ejj ,coal1 bitum9\s1 av]age #ai1jjj #g1jjj ,gasol9e #ai1jjj #aj1eej ,illum9at+ gas #ah1jjj #aj1jjj ,k]os5e #ai1iij #aa1jej ---------------------------------------- ----- ,,con/ants ,,= ,,heat ,,transmission ,data f ,ideal ,fitt]1 ,am]ican ,radiator ,co4 ,b4t4u4 transmitt$ p] squ>e foot p] h\r p] degree 7,fahr5heit7 diff]5ce 9 temp]ature betwe5 inside & outside air4 ,brick "w #d 94 ?ick #j4fh concrete #h 94 ?ick #j4df cem5t #ej p] c5t4 m ?an brick4 #ab 94 ?ick #j4cc /one #cc-a_/c p] c5t4 m ?an brick4 ,w9d[ #a4jij ,wood z wall #j4bbj concrete #bj p] c5t4 m ?an ,d\ble w9d[ #j4efj re9=c$ brick4 ,important ,topics #a4 ,heat a manife/ation ( en]gy4 #b4 ,/eam-eng9e & its action4 #c4 ,me*anical equival5t ( heat & heat equival5t ( fuels & effici5cy ( eng9es4 ,ex]cises #a4 ,con/ruct a work+ model ( ! cyl9d] & /eam *e/ ( a /eam eng9e & be prep>$ to expla9 its action4 #b4 ,at #e4jj p] ton h[ _m ,b4,t4,u4's %\ld be produc$ f #a c5t's wor? ( bitum9\s coal8 #c4 ,try ! foll[+ exp]im5t3 ,place a qu>t ( wat] 9 a teakettle & place x ov] ! fire = #e m9utes1 & note ! rise 9 temp]ature & compute ! numb] ( ,b4,t4,u4's ent]+ ! wat]4 ,place ano!r qu>t ( wat] at ! same temp]ature 9 an alum9um or t9 di% & heat = #e m9utes1 note ! rise 9 temp]ature & compute ! heat us$ be=e4 ,:i* ( ! di%es %[s ! great] effici5cy8 ,h[ d ! effici5cies ( ! two di%es comp>e8 ,h[ d y acc\nt = any diff]5ces 9 ! effici5cies f\nd8 #d4 ,h[ high w\ld #h cu4 ft4 ( wat] be lift$ if all ( ! en]gy produc$ by burn+ #a lb4 ( coal 7 us$ 9 rais+ x8 #e4 ,:at is ! me*anical equival5t ( a p\nd ( coal express$ 9 horse-p[] h\rs8 #f4 ,if a furnace burns #ajj lbs4 ( coal a day & its effici5cy is #ej p] c5t4 h[ _m ,b4,t4,u4's are us$ 9 w>m+ ! h\se8 #g4 ,h[ _m ,b4,t4,u4's c be obta9$ by burn+ #a_/b ton ( bitum9\s coal8 #h4 :5 a p\nd ( wat] is heat$ f #dj;,f4 to #bab;,f41 h[ _m foot-p\nds ( en]gy are absorb$ by ! wat]8 #i4 ,h[ _m loads ( coal ea* weigh+ #b tons1 c\ld be lift$ #ab ft4 by ! en]gy put into ! wat] 9 problem #h8 ,illu/ration3 ,,fig4 #afc4--;,an ecc5tric4 #aj4 ,:5 #c cu4 ft4 ( wat] are us$ = a hot ba? & ! wat] has be5 heat$ f #ej;,f4 to #aab;,f41 h[ _m ,b4,t4,u4's h be5 absorb$ by ! wat]8 #aa4 ,if ! av]age temp]ature ( wat] at ! surface ( ,lake ,mi*igan is #ej;,f41 h[ _m ,b4,t4,u4's w\ld be giv5 (f by ea* cubic foot ( wat] at ! surface1 if ! temp]ature ( ! wat] %\ld drop #e;,f48 #ab4 ,9 a cold /orage plant c>bon dioxide gas is us$4 ,! pipe lead+ f ! compression pump to ! expansion valve passes ?r\gh a cond5s+ tank ( cold wat]4 ,:y8 #ac4 ,:5 ! gas is compress$ 9 a cold /orage plant1 :at becomes ( ! en]gy us$ by ! compression pump8 #ad4 ,an ecc5tric 7,fig4 #afc71 is a r\nd disc m\nt$ a little to "o side ( its c5t]1 ,a1 on ! eng9e %aft ,b4 ,a b&1 ,c1 on ! circumf]5ce ( ! disc is connect$ by a rod1 ,d1 ) ! slide valve 9 ! /eam *e/4 ,h[ is ! rot>y motion ( ! %aft *ang$ into a backw>d & =w>d motion ( ! slide valve8 7#d7 ,,heat ,,eng9es #aif4 ,! ,gas ,eng9e4--,"o ( ! heat eng9es 9 common use to-day is ! gasol9e eng9e4 ,x is us$ to propel automobiles & motor boats1 to drive ma*9]y1 etc4 ,! con/ruction & action ( a gasol9e eng9e may be und]/ood by /udy+ a work+ model1 or by prop] diagrams4 ,illu/ration3 ,,fig4 #afd4--;,cut away view ( a mod]n automobile eng9e1 ) p>ts requir+ att5tion mo/ frequ5tly1 indicat$4 7,c\rtesy ( ! ,automobile ,j\rnal7 ,! common gasol9e or gas eng9e is call$ a f\r-cycle 7bett] f\r-"p cycle7 eng9e 7see ,fig4 #afd71 s9ce x requires f\r movem5ts ( ! pi/on to complete "o cycle or s]ies ( *anges4 ,?is is illu/rat$ 9 ,fig4 #afe #a1 :i* repres5ts a cross-section ( ! cyl9d] ( ! gasol9e eng9e ) ! pi/on mov+ d[nw>d4 ,at ! upp] end ( ! cyl9d] are two ports or op5+s4 ,"o1 ! exhau/ port1 is clos$1 ! inlet port is op5 & a mixture ( gas & air is ent]+4 ,fig4 #afe #b %[s ! pi/on return+2 bo? ports are clos$ & ! *>ge ( air & gas is be+ compress$4 ,z ! pi/on rea*es ! end ( its /roke 9 compress+ ! *>ge1 an electric sp>k explodes or fires ! *>ge ( gas & air4 ,! hot burn+ gas exp&s sudd5ly driv+ ! pi/on d[nw>d ) great =ce 7,fig4 #afe #c74 ,! pi/on rod is atta*$ to ! crank ( a heavy fly-:eel & ?is is giv5 suffici5t en]gy or mom5tum to keep x go+ ?r\gh ! next ?ree /rokes4 ,fig4 #afe #d repres5ts ! return+ pi/on pu%+ out ! burnt *>ge ?r\gh ! op5 exhau/ valve e4 ,on ! next d[nw>d motion ( ! pi/on ! valve e closes4 ,x op5s1 & new *>ges ( gas & air ent] & ! cycle is repeat$4 ,illu/ration3 ,,fig4 #afe4--,! f\r /rokes ( a gas eng9e cycle4 ,9 ord] to make ! motion m ev5 & cont9u\s & also to secure m p[]1 m ?an "o cyl9d] is atta*$ to ! same %aft & fly-:eel4 ,two1 ?ree1 f\r1 six1 eight & ev5 m cyl9d]s h be5 atta*$ to "o %aft4 ,f\r or six cyl9d]s are commonly us$ 9 automobile gasol9e motors4 ,to less5 ! s\nd ( ! exhau/1 ! latt] is s5t ?r\gh a muffl] :i* (t5 r$uces ! noise to a l[ ?robb+4 7,see ,fig4 #aff47 ,! gasol9e eng9e is m effici5t ?an ! /eam-eng9e1 s9ce ! fuel1 gas1 is burn$ 9 ! cyl9d] & n 9 a sep>ate furnace4 ,! combu/ion ( ! fuel 9 ! cyl9d]s makes "s special cool+ device necess>y to prev5t _! ov]heat+4 ,?is usually consi/s ( a cas+ ab\t ! cyl9d]s4 ,betwe5 ! cyl9d] & ?is cas+ is wat] :i* on be+ heat$ passes to a tank or radiator4 ,9 ! radiator ! wat] cools & !n returns to ! space betwe5 ! cyl9d]s & cas+ ?us keep+ up ! circulation4 ,illu/ration3 ,,fig4 #aff4--;,an effici5t automobile muffl]4 7,c\rtesy ,popul> ,sci5ce ,mon?ly47 #aig4 ,effici5cy ( ,gas ,eng9es4--,"o may te/ ! effici5cy ( a gas eng9e by det]m9+ ! am\nt ( p[] develop$ & comp>+ x ) ! me*anical equival5t ( ! fuel burn$4 ,illum9at+ gas is sometimes employ$ to drive gas eng9es4 ,"o cubic foot ( illum9at+ gas %\ld produce #fjj ,b4,t4,u4 :5 burn$4 ,! effici5cy ( ! gas or gasol9e eng9es is sometimes z high z #be p] c5t4 ,?is eng9e is free f smoke & is also compact & quickly />t$4 ,:ile ! fuel1 gas or gasol9e1 is some:at exp5sive x is light & easily c>ri$4 ,suppose a gas eng9e produces #a horse-p[] & uses #bj cu4 ft4 ( gas an h\r1 :at is its effici5cy8 #a horse-p[]-h\r #eej #fj #fj #a1ihj1jjj ft4-lbs4 #bj cu4 ft4 ( gas #bj #fjj #ggh #i1ccf1jjj ft4-lbs4 ,effici5cy "w out_/"w 9 #a1ihj1jjj_/i1ccf1jjj #ba4b p] c5t4 ,illu/ration3 ,,fig4 #afg4--,! pr9ciple ( ! /eam turb9e4 ,illu/ration3 ,,fig4 #afh4--,pa? ( /eam 9 ,de,laval /eam turb9e4 7a7 & 7c7 movable blades1 7b7 /ation>y4 #aih4 ,! ,/eam ,turb9e4 ,"o =m ( ! /eam-eng9e t is com+ into g5]al use is ! turb9e4 7,see ,fig4 #afg47 ,?is consi/s ( a %aft to :i* are atta*$ blades1 ! %aft & blades be+ conta9$ 9 a clos$ case4 ,/eam is admitt$ by nozzles & /rikes ! blades s z to set !m & ! %aft 9 motion4 ,!re are also /ation>y blades 7see ,fig4 #afh71 :i* assi/ 9 direct+ ! /eam effectively aga9/ ! rotat+ p>ts4 ,! /eam turb9e is us$ = l>ge p[] plants4 7,see ,fig4 #bic47 ,x is v effici5t1 makes v little vibration1 & occupies ab\t "o-t5? ! floor space t a reciprocat+ eng9e ( equal p[] uses4 ,"s l>ge ocean /eam]s are n[ driv5 by /eam turb9es4 ,important ,topics #a4 ,! gas eng9e1 its con/ruction1 action & effici5cy4 #b4 ,! /eam turb9e4 ,ex]cises #a4 ,if coal co/s #d4jj a ton1 & gas1 #j4hj p] #ajjj cu4 ft4 :at am\nts ( heat c be secur$ f #a c5t's wor? ( ea*8 #b4 ,:at w x co/ to heat #cj gallons ( wat] 7#a gal4 ( wat] weighs ab\t #h-a_/c lbs47 f #dj;,f4 to #aij;,f4 ) coal co/+ #d4jj p] ton & yield+ #ab1jjj ,b4,t4,u4 p] lb4 if ! heat] has an effici5cy ( #ej p] c5t4 #c4 ,:at w x co/ to heat #cj gallons ( wat] f #dj;,f4 to #aij;,f4 ) gas at #j4hj p] #ajjj cu4 ft4 if ! heat+ device has an effici5cy ( #ge p] c5t4 #d4 ,con/ruct a c>dbo>d work+-model %[+ ! action ( ! gas eng9e & be prep>$ to expla9 ! action ( ! v>i\s p>ts4 #e4 ,if #ejj lbs4 ( iron %\ld fall #bjjj ft4 & all ( ! result+ me*anical k9etic en]gy %\ld be trans=m$ into heat1 :at w\ld be ! am\nt ( heat produc$8 #f4 ,:at are ! special advantages ( 7a7 ! gasol9e eng9e8 7b7 ! turb9e8 7c7 ! reciprocat+ /eam eng9e8 #g4 ,d y burn coal or gas 9 y\r kit*5 /ove at home8 ,:i* is = y ! m economical8 ,:y8 #h4 ,:at are ! advantages ( us+ a fireless cook]8 #i4 ,:at is ! effici5cy ( a locomotive t burns #c4b lbs4 ( coal p] horse-p[]-h\r8 #aj4 ,a gas eng9e develop$ 9 a te/ #j4cd horse-p[] = #a m9ute4 & #ej seconds1 #j4e cu4 ft4 ( gas be+ us$4 ,! heat ( combu/ion ( ! gas 0 #fjj ,b4,t4,u4 p] cu4 ft4 ,f9d ! effici5cy ( ! eng9e4 #aa4 ,f9d ! horse-p[] ( an eng9e1 ! diamet] ( ! pi/on be+ #ai 941 /roke #bf 942 x uses /eam at an av]age pressure ( #bjj lbs4 p] squ>e4 in* & makes #ajj /rokes a m9ute4 #ab4 ,:at is ! effici5cy ( an eng9e & boil] t develops #bjj horse-p[]1 :ile burn+ #cij lbs4 ( s(t coal p] h\r8 #ac4 ,if a locomotive has an effici5cy ( #f p] c5t4 & develops #agjj horse-p[] h[ mu* coal is burn$ 9 an h\r8 #ad4 ,if an automobile eng9e burns #a gallon ( gasol9e 9 an h\r & develops #aj horse-p[]1 :at is its effici5cy8 #ae4 ,! ,a4,l4,a4,m4,j =mula = horse-p[] is 7,n ,b7_/#b4e :5 ! pi/on spe$ is #ajjj ft4 p] m9ute1 ,n be+ ! numb] ( cyl9d]s & ,b1 _! diamet]4 ,f9d ! horse-p[] ( a #d-;cyl9d] eng9e1 ! cyl9d]s hav+ a diamet] ( #d 94 ,j ,am]ican ,league ( ,automobile ,manufactur]s4 #af4 ,f9d ! horse-p[] ( a #f-;cyl9d] automobile eng9e1 if ! cyl9d] diamet] is #d4e 94 #ag4 ,a #d-;cyl9d] automobile hav+ #d-;94 cyl9d]s1 uses #a gallon ( gasol9e 9 #a h\r4 ,f9d its effici5cy1 if its av]age horse-p[] develop$ is #f4 #ah4 ,! motor boat ,di/urb] ,,iii1 has #bd cyl9d]s ea* ) diamet] #c4e 94 ,if ! pi/on spe$ is #ajjj ft4 p] m9ute1 :at is ! horse-p[]8 7,see problem #ae47 ,review ,outl9e3 ,heat ,heat2 s\rces 7#d71 effects 7#e71 units 7#b74 ,temp]ature2 !rmomet] scales 7#c71 absolute temp]ature1 #i;,c_/#e #cb ,f4 ,expansion2 gases1 ,law ( ,*>les 7,v#a_/,v#b ,t#a_/,t#b71 liquids1 peculi>ity ( wat]1 solids1 coeffici5t ( expansion1 uses1 results4 ,heat ,transf]5ce2 conduction1 uses ( good & poor conductors1 convection1 9 nature1 heat+ & v5tilat+ sy/ems1 radiation1 #c peculi>ities1 value ( sun's radiation4 ,heat & ,moi/ure2 relative humidity1 dew po9t1 =mation ( dew1 fog1 ra91 sn[1 etc41 evaporation1 effects1 conditions4 ,heat ,measurem5t2 specific heat1 heat ( fusion1 ( vaporization1 combu/ion4 ,vaporization2 ,boil+ po9t1 laws ( boil+1 di/illation1 artificial cool+4 ,heat ,eng9es2 /eam1 gas4--con/ruction1 action1 effici5cy1 me*anical equival5t ( heat4 ,heat equival5t ( fuels4 ,,*apt] ,,ix ,,magnetism 7#a7 ,,g5]al ,,prop]ties ,,( ,,magnets #aii4 ,magnets4--,s9ce ! times ( ! e>ly ,greek philosoph]s m5 h kn[n ( c]ta9 /ones t h ! prop]ty ( attract+ to !mselves objects ( iron & /eel4 ,su* /ones are call$ natural magnets4 ,x is ?\ght by _m t ! "n magnet is d]iv$ f ,magnesia 9 ,asia ,m9or1 :]e ^! /ones are abundant1 ?\gh ?is is b tradition4 ,x 0 also le>n$ long ago t iron & /eel objects :5 rubb$ ) natural magnets become magnetiz$1 t is1 acquire ! prop]ties ( magnets4 ,^! are said to be artificial magnets4 ,illu/ration3 ,,fig4 #afi4--;,a b> magnet4 ,illu/ration3 ,,fig4 #agj4--;,a horse%oe magnet4 ,"s #hjj ye>s ago x 0 discov]$ t magnets1 natural or artificial1 :5 susp5d$ s z to turn freely1 always come to re/ 9 a def9ite position po9t+ approximately nor? or s\?4 ,?is is especially noticeable :5 ! magnet is long & n>r[4 ,because ( ?is prop]ty ( indicat+ direction1 natural magnets 7 giv5 ! "n ( lode/one 7lode-lead+74 ,artificial magnets are made by rubb+ /eel b>s ) a magnet or by plac+ ! /eel b> 9 a coil ( wire ?r\gh :i* a curr5t ( electricity is fl[+4 ,! magnetiz$ /eel b>s may h any =m1 usually !y are ei!r /raight or b5t into a ,u %ape4 ,^! =ms are kn[n z b> & horse%oe magnets4 7,see ,figs4 #afi & #agj47 ,magnets reta9 _! /r5g? be/ :5 provid$ ) s(t-iron keep]s1 z 9 ,fig4 #aga4 ,illu/ration3 ,,fig4 #aga4--;,b> magnets ) keep]s4 #bjj4 ,magnetic ,poles4--,if a magnet is plac$ 9 iron fil+s & remov$1 ! fil+s w be f\nd to cl+ /rongly at places ne> ! ends ( ! magnet1 b = a portion ( its l5g? ne> ! middle no attraction is f\nd4 7,see ,fig4 #agb47 ,^! places ( greate/ attraction on a magnet are call$ poles4 ,if a b> magnet is susp5d$ s z to sw+ freely ab\t a v]tical axis ! magnetic pole at ! end po9t+ nor? is call$ ! nor?-seek+ pole2 at ! o!r end1 is ! s\?-seek+ pole4 ,9 mo/ places ! ne$le does n po9t to ! true nor?1 b some:at to ! ea/ or we/ ( nor?4 ,! direction tak5 by a magnetic ne$le is p>allel to ! magnetic m]idian4 ,illu/ration3 ,,fig4 #agb4--;,iron fil+s attract$ to ! poles ( a magnet4 #bja4 ,law ( ,magnetic ,action4--,! nor? pole ( a magnet is usually m>k$4 ,if a m>k$ b> magnet be held 9 ! h& & its nor?-seek+ pole be br\ght ne> ! nor?-seek+ pole ( a freely susp5d$ b> magnet1 ! two poles w be f\nd to repel ea* o!r1 z w also two s\?-seek+ poles1 :ile a nor?-seek+ & a s\?-seek+ pole attract ea* o!r4 7,see ,fig4 #agc47 ,?is action leads to ! /atem5t ( ! ,law ( ,magnetic ,action3 ,l poles repel1 :ile unlike poles attract ea* o!r4 ,! =ce ( attraction or repulsion less5s z ! di/ance increases4 ,! =ce ( ! action betwe5 magnetic poles is inv]sely proportional to ! squ>e ( ! di/ance betwe5 !m4 ,comp>e ?is ) ! law ( gravitation 7,art4 #hh74 ,illu/ration3 ,,fig4 #agc4--,l poles ( two magnets repel4 ,illu/ration3 ,,fig4 #agd4--;,a magnetoscope4 #bjb4 ,magnetic ,sub/ances & ,prop]ties4--,x is f\nd t if an iron or /eel magnet is heat$ r$ hot t its magnetic prop]ties disappe>4 ,accord+ly "o me?od ( demagnetiz+ a magnet is to raise x to a r$ heat4 ,if a magnet t has be5 heat$ r$ hot & !n cool$ is br\ght ne> a susp5d$ b> magnet1 x is f\nd to attract ei!r end1 %[+ t x has rega9$ magnetic prop]ties ev5 ?\gh x has lo/ its magnetic pol>ity4 ,a susp5d$ b> magnet us$ to te/ ! magnetic prop]ties ( a body is call$ a magnetoscope4 7,see ,fig4 #agd47 ,! ne$le ( a magnetic compass s]ves v well z a magnetoscope4 ,magnetic prop]ties are mo/ /rongly exhibit$ by iron & /eel1 ?\gh nickel & cobalt %[ "s magnetic effects4 ,!re is a peculi> alloy ( copp]1 alum9um1 & manganese1 kn[n z ,heusl]'s ,alloy1 t is also magnetic4 ,h[ev]1 ( all sub/ances1 iron & /eel %[ ! /ronge/ magnetic effects4 #bjc4 ,magnetic ,induction4--,let ! nor?-seek+ pole ( a b> magnet support an iron nail by its head4 7,see ,fig4 #age47 ,te/ ! po9t ( ! nail = pol>ity4 ,see :e!r a second nail c be atta*$ by its head to ! po9t ( ! fir/4 ,te/ ! pol>ity ( ! po9t ( ?is nail4 ,f9d by trial h[ _m nails c be susp5d$ 9 succession f ! magnet4 ,te/ 9 ea* case = pol>ity4 ,)draw c>efully ! magnet f ! fir/ nail--! /r+ ( nails w fall ap>t4 ,repeat ! te/ ) a ?ickness ( pap] betwe5 ! magnet & ! fir/ nail4 ,results simil> to ^? secur$ at fir/ w be f\nd1 ?\gh probably few] nails w be support$4 ,! pres5ce ( pap] betwe5 ! magnet & nails simply weak5s ! action4 ,te/ ! action ( ! magnet ^u ! nail :5 !re is betwe5 !m a piece ( glass1 "o's ?umb1 ?9 pieces ( wood1 copp]1 z9c1 etc4 ,! magnetiz+ ( a piece ( iron or /eel by a magnet ne> or t\*+ x is call$ magnetic induction4 ,?is action takes place ?r\gh all sub/ances except l>ge bodies ( iron or /eel h5ce ^! sub/ances are (t5 us$ z magnetic scre5s4 ,! pole ( ! new induc$ magnet adjac5t to ! b> magnet is j opposite to ! pole us$4 ,?us ! ,n4-pole ( ! magnet us$ w produce a ,s4-pole at ! ne> end ( ! nail & a ,n4-pole at ! end f>!r away4 7,see ,fig4 #age47 ,on remov+ ! magnet1 ! nails are f\nd to reta9 a "p ( _! induc$ magnetism4 ,illu/ration3 ,,fig4 #age4--,nails magnetiz$ by induction4 #bjd4 ,ret5tivity4--,9 sev]al ( ! =ego+ p>agraphs x has be5 se5 t a piece ( iron or /eel :5 once magnetiz$ does n entirely lose its magnetism :5 ! magnetiz+ =ce is remov$4 ,diff]5t pieces ( iron & /eel v>y greatly 9 ?is respect1 "s rema9+ /rongly magnetiz$1 o!rs los+ mu* ( _! magnetism4 ,?is prop]ty ( reta9+ magnetism is call$ ret5tivity4 ,h>d5$ /eel has a high degree ( ret5tivity1 :ile s(t iron reta9s b little magnetism4 ,important ,topics #a4 ,magnet2 natural1 artificial1 b>1 horse%oe4 #b4 ,magnetic poles2 nor? seek+1 s\? seek+4 #c4 ,law ( action1 magnetoscope1 ret5tivity1 induc$ magnet4 ,ex]cises #a4 ,make a summ>y ( ! facts ( magnetism pres5t$ 9 ?is lesson4 #b4 ,is magnetism matt]1 =ce1 or en]gy8 ,h[ d y decide8 ,to :at o!r ph5om5on t we h /udi$ is x simil>8 ,h[8 #c4 ,make a simple magnetoscope = y\rself by susp5d+ a ?9 /eel ne$le or rod #e to #aj cm4 long1 ) a light ?read or silk fib] at its c5t]1 s t x w hang level4 ,!n magnetize ! ne$le1 & keep ! magnetoscope 9 y\r book4 #d4 ,"n ?ree uses = magnets or magnetism4 #e4 ,m5tion ?ree uses = a magnetoscope4 #f4 ,are all magnets produc$ by induction8 ,expla94 #g4 ,9 :at magnetic devices is a high ret5tivity desirable8 7#b7 ,,! ,,!ory ,,( ,,magnetism ,,& ,,magnetic ,,fields #bje4 ,! ,!ory ( ,magnetism4--,if a magnetiz$ wat* spr+ is brok5 9 two1 ea* "p is f\nd to be a magnet4 ,if "o ( ^! p>ts be brok5 & ?is process ( break+ be cont9u$ z f> z possible1 ! smalle/ "p obta9$ has two poles & is 9 fact a complete magnet4 7,see ,fig4 #agf47 ,x is suppos$ t if ! division c\ld be cont9u$ f> en\gh t ea* ( ! molecules ( ! /eel spr+ w\ld be f\nd to h two poles & to be a magnet4 ,9 o!r words1 magnetism is believ$ to be molecul>4 ,o!r evid5ce support+ ?is idea is f\nd 9 ! fact t :5 a magnet is heat$ r$ hot1 to a temp]ature ( viol5t molecul> motion1 its magnetism disappe>s4 ,also if a long1 f9e s(t iron wire be /rongly magnetiz$1 a light j> causes its magnetism to disappe>4 ,?is w\ld lead u to believe t magnetism is n a prop]ty ( ! surface ( ! body1 b t x dep5ds ^u molecul> /ructure or ! arrangem5t ( ! molecules4 ,illu/ration3 ,,fig4 #agf4--;,effect ( break+ a magnet4 ,illu/ration3 ,,fig4 #agg4--,possible arrangem5t ( molecules 9 an unmagnetiz$ iron b>4 ,x is believ$ also t ! molecules ( a magnetic sub/ance are magnets at all times2 t be=e ! body is magnetiz$ ! molecules are arrang$ haphaz>d 7see ,fig4 #agg7 b t :5 a magnet is br\ght ne>1 ! molecules t5d to arrange !mselves 9 l9e1 ) _! nor?-seek+ poles po9t+ 9 ! same direction4 7,see ,fig4 #agh47 ,if ! magnet is j>r$ "s ( ! molecules t5d to get out ( l9e1 p]haps to =m little clos$ *a9s ( molecules4 7,see ,fig4 #agg47 ,illu/ration3 ,,fig4 #agh4--;,arrangem5t ( molecules 9 a saturat$ magnet4 #bjf4 ,magnetic ,fields & ,l9es ( ,=ce4--,! behavior ( magnets is bett] und]/ood aft] obs]v+ & /udy+ ! l9es ( =ce ( a magnet4 ,! e>lie/ descriptions ( ^! are by ,william ,gilb]t1 ! fir/ ,engli%man to appreciate fully ! value ( mak+ exp]im5tal obs]vations4 ,he wrote a book 9 #afjj call$ ,de ,magnete 9 :i* he publi%$ 8 exp]im5ts & discov]ies 9 magnetism4 7,see p4 #bag47 ,magnetic l9es ( =ce may be obs]v$ by plac+ a magnet ^u ! table1 !n lay+ ^u x a %eet ( pap] & spr9kl+ ov] ! latt] f9e iron fil+s4 ,on g5tly tapp+ ! pap]1 ! fil+s arrange !mselves along curv$ l9es ext5d+ f "o end ( ! magnet to ! o!r4 ,^! are call$ ! magnetic l9es ( =ce4 7,see ,fig4 #agi47 ,! space ab\t a magnet 9 :i* ! magnetic l9es are f\nd is call$ ! magnetic field4 7,see ,fig4 #ahj47 ,illu/ration3 ,,fig4 #agi4--;,iron fil+s on pap] ov] a b> magnet4 ,_m int]e/+ ?+s h be5 discov]$ conc]n+ ! l9es ( =ce4 ,"s ( ! facts ( magnetic action are giv5 a simple explanation if we ?9k ( !m z due to ! magnetic l9es ( =ce4 ,a summ>y ( sev]al discov]ies conc]n+ magnetic fields foll[s3 7,a7 ,magnetic l9es ( =ce run side by side & d n cross "o ano!r4 7,see magnetic fields47 7,b7 ,magnetic l9es ( =ce are believ$ to =m clos$ curves or to be cont9u\s4 ,! "p outside ( ! magnet is a cont9uation ( ! "p )9 ! magnet4 7,see ,fig4 #ahj47 ,illu/ration3 ,,fig4 #ahj4--;,diagram ( ! field ( a b> magnet4 7,c7 ,! attraction ( a magnet is /ronge/ :]e ! magnetic l9es are ?icke/1 h5ce !y are believ$ to be ! means by :i* a magnet attracts4 7,d7 ,s9ce l poles repel & unlike poles attract1 x is kn[n t ! action along a l9e ( =ce is n ! same 9 bo? directions4 ,x has !re=e be5 agre$ by physici/s to indicate by an arr[ head 7,fig4 #ahj71 ! direction t a nor?-seek+ pole t5ds to move along a l9e ( =ce4 ,! l9es ( =ce are consid]$ z leav+ ! nor?-seek+ pole ( a magnet & ent]+ ! s\?-seek+ pole4 7,see ,figs4 #aha & #ahb47 ,illu/ration3 ,,fig4 #aha4--,magnetic field betwe5 l poles %[+ repulsion4 7,e7 ,a freely susp5d$ small magnet 9 a magnetic field places itself p>allel to ! l9es ( =ce4 7,te/ ?is by hold+ a magnetic compass 9 diff]5t portions ( a magnetic field74 ,note ! position ( ! ne$le & ! l9es ( =ce4 ,?is fact indicates t ! compass ne$le po9ts nor? on acc\nt ( its t5d5cy to turn s z to be p>allel to ! e>?'s magnetic held4 ,illu/ration3 ,,fig4 #ahb4--,magnetic field betwe5 unlike poles %[+ attraction4 7,f7 ,ea* magnet is accompani$ by its own magnetic field4 ,:5 a piece ( iron is br\ght )9 ! field ( a magnet ! l9es ( =ce pass+ ?r\gh ! iron t5d to arrange ! iron molecules 9 l9e or to magnetize ! iron4 #bjg4 ,magnetic ,induction4--,! action ( magnetic l9es ( =ce 9 magnetiz+ iron :5 !y pass ?r\gh x1 is call$ ,magnetic ,induction4 ,?is may n[ be def9$ z ! production ( magnetism 9 a body by plac+ x )9 a magnetic field4 ,freely susp5d$ magnets place !mselves p>allel to ! l9es ( =ce 9 a magnetic field1 !re=e :5 an iron rod is plac$ 9 a weak field1 or "o ) few l9es ( =ce1 ! iron is b slightly magnetiz$2 t is1 b few molecules are br\ght into l9e4 ,increas+ ! /r5g? ( ! magnetiz+ field1 gives /rong] magnetization to ! iron up to a c]ta9 po9t4 ,aft] ?is1 /rong] fields give no increase 9 magnetiz+ effect4 ,:5 iron exhibits its greate/ magnetization x is said to be saturat$4 ,illu/ration3 ,,fig4 #ahc4--;,effect ( a piece ( iron 9 a magnetic field4 #bjh4 ,p]meability4--,if a piece ( iron is plac$ betwe5 ! poles ( a horse%oe magnet1 ! field obta9$ by spr9kl+ iron fil+s ^u a %eet ( pap] ov] ! magnet resembles t %[n 9 ,fig4 #ahc4 ,! l9es 9 ! space betwe5 ! poles ( ! magnet seem to cr[d 9 to ! piece ( iron4 ,! prop]ty ( ! iron by :i* x t5ds to conc5trate & increase ! numb] ( l9es ( =ce ( a magnetic field is call$ p]meability4 ,s(t iron %[s high p]meability4 ,m>k$ diff]5ces 9 behavior are %[n by diff]5t k9ds ( iron & /eel :5 plac$ 9 a magnetic field4 ,v pure iron1 or s(t iron1 is /rongly magnetiz$ by a magnetic field ( m$ium /r5g?4 ,its magnetism1 h[ev]1 is quickly lo/ :5 ! magnetiz+ field is remov$4 ,?is indicates t s(t-iron molecules are easily swung into l9e1 b also dis>range !mselves z easily :5 remov$ f a magnetiz+ =ce4 ,s(t-iron magnets hav+ high p]meability quickly lose _! magnetism4 ,!y are !re=e call$ tempor>y magnets4 ,on ! o!r h& a h>d5$ /eel b> is difficult to magnetize1 b :5 once magnetiz$ reta9s its magnetism p]man5tly1 unless "s action weak5s ! magnet4 ,su* magnets are call$ p]man5t magnets4 ,,note4--,! t]m l9e ( =ce z us$ 9 ?is text means ! same z l9e ( induction z us$ 9 m advanc$ texts4 ,important ,topics #a4 ,molecul> !ory ( magnetism1 saturation1 p]meability4 #b4 ,magnetic fields & l9es ( =ce4 #c4 ,six facts conc]n+ magnetic fields4 ,ex]cises #a4 ,"n an object ^: usefulness dep5ds ^u its ret5tivity4 ,expla94 #b4 ,h[ d y expla9 ! ret5tivity ( h>d /eel8 #c4 ,are ! molecules ( a piece ( iron magnetiz$ at all times8 ,expla94 #d4 ,:5 a piece ( iron is magnetiz$ by induction does any magnetism ent] ! iron f ! magnet8 ,does ! magnet lose z ! iron ga9s magnetism8 ,expla94 #e4 ,h all magnets be5 produc$ by induction8 ,expla94 #f4 ,:y w tapp+ a piece ( iron :5 9 a magnetic field increase ! am\nt x w be magnetiz$8 #g4 ,express 9 y\r own words ! !ory ( magnetism4 #h4 ,place two b> magnets 9 a l9e #e cm4 ap>t1 unlike poles adjac5t2 obta9 ! magnetic field ) iron fil+s4 ,sket* x4 #i4 ,repeat ,ex]cise ,no4 #h us+ l poles4 ,describe ! appe>ance ( a field t gives attraction2 ( a field t gives repulsion4 7#c7 ,,! ,,e>?',s ,,magnetism #bji4 ,! ,e>?'s ,magnetic ,field4--,dr4 ,william ,gilb]t's fam\s book1 ,de ,magnete1 conta9s _m helpful & sugge/ive ideas1 none p]haps m important ?an 8 explanation ( ! behavior ( ! compass ne$le4 ,he assum$ t ! e>? is a magnet1 ) a s\?-seek+ pole ne> ! geographical nor? pole1 & ) a nor?-seek+ pole ne> ! geographical s\? pole4 ,?is idea has s9ce be5 %[n to be correct4 ,! nor? magnetic 7or s\?-seek+7 pole 0 f\nd 9 #ahca1 by ,sir ,james ,ross 9 ,boo?ia ,felix1 ,canada4 ,its approximate pres5t location z det]m9$ by ,capta9 ,amunds5 9 #aije is latitude #gj #e ,n4 & longitude #if #df ,w4 ,! s\? magnetic pole is 9 latitude #gb ,s41 longitude #aee #af ,e4 ,! nor? magnetic pole is cont9ually *ang+ its position4 ,at pres5t x is mov+ sl[ly we/w>d4 ,illu/ration3 ,,fig4 #ahd4--,magnetic map ( ! e>? = #aiaj4 ,isogonic l9es ------ ,isocl9ic l9es - - - - #baj4 ,direction ( ! ,e>?'s ,magnetic ,field4--,ref]5ce has be5 made to ! fact t ! compass does n always po9t exactly nor?4 ,?is indicates t ! e>?'s magnetic field v>ies 9 its direction4 ,columbus discov]$ ?is fact ^u 8 fir/ voyage4 ,! discov]y al>m$ ! sailors s9ce !y fe>$ !y might come to a place :]e ! compass w\ld be unreliable4 ,?is v>iation is call$ decl9ation4 ,x is def9$ z ! angle betwe5 ! direction ( ! ne$le & ! geographical m]idian4 ,decl9ation is due to ! fact t ! geographical & magnetic poles d n co9cide4 ,:at is meant by a decl9ation ( #ij8 ,l9es drawn ^u a map s z to pass ?r\gh places ( ! same decl9ation are call$ isogonic l9es4 ,! l9e pass+ ?r\gh po9ts :]e ! ne$le po9ts nor?1 )\t decl9ation1 is ! agonic l9e4 ,! agonic l9e is sl[ly mov+ we/w>d4 ,x n[ passes ne> ,lans+1 ,mi*igan2 ,c9c9nati1 ,ohio2 & ,*>le/on1 ,s4 ,c>ol9a4 7,see ,fig4 #ahd47 ,at all po9ts 9 ! ,unit$ ,/ates & ,canada ea/ ( ! agonic l9e ! decl9ation is we/1 at po9ts we/ ( ! agonic l9e ! decl9ation is ea/4 #baa4 ,! ,dipp+ ,ne$le4--,m\nt an unmagnetiz$ /eel ne$le on a horizontal axis s z to be 9 neutral equilibrium1 t is1 s z to rema9 balanc$ 9 any position 9 :i* x is left4 ,^u be+ magnetiz$ & plac$ s t x c sw+ 9 a nor? & s\? plane1 ! nor?-seek+ pole w n[ be f\nd to be depress$1 ! ne$le =m+ an angle ( ne>ly #gj ) ! horizontal4 7,see ,fig4 #ahe47 ,! position assum$ by ! ne$le indicates t ! e>?'s magnetic field in/ead ( be+ horizontal 9 ! ,unit$ ,/ates dips d[n at an angle ( ab\t #gj4 ,ov] ! magnetic pole1 ! dipp+ ne$le z x is call$1 is v]tical4 ,at ! e>?'s equator x is ne>ly horizontal4 ,! angle betwe5 a horizontal plane & ! e>?'s magnetic l9es ( =ce is call$ ! incl9ation or dip4 ,illu/ration3 ,,fig4 #ahe4--;,a dipp+ ne$le4 #bab4 ,inductive ,effect ( ! ,e>?'s ,magnetic ,field4--,! e>?'s magnetic l9es ( =ce are to be consid]$ z fill+ ! space above ! e>?1 pass+ ?r\gh all objects on ! surface & into & ?r\gh ! e>?'s int]ior4 ,! direction ( ! e>?'s field is %[n by ! compass & ! dipp+ ne$le4 ,magnetic l9es ( =ce t5d to cr[d into & foll[ iron & /eel objects on acc\nt ( _! p]meability4 ,!re=e1 iron or /eel objects1 su* z po/s1 columns1 etc41 are p]meat$ by ! e>?'s l9es ( =ce1 :i* 9 ! ,unit$ ,/ates ent] at ! top ( ^! objects & leave at ! bottom4 ,! l9es ( =ce pass+ ?r\gh ^! bodies arrange _! molecules 9 l9e or magnetize ! bodies4 ,! inductive effect ( ! e>?'s magnetism indicates h[ lode/ones or natural magnets acquire _! magnetiz$ condition4 ,s f> z is kn[n1 magnetism produces no effect ^u ! human body4 ,x c !re=e be /udi$ only by obs]v+ its effects ^u magnets or bodies affect$ by x4 ,important ,topics ,! e>?'s magnetic field1 dip1 decl9ation1 agonic l9e1 induction by ! e>?'s field4 ,ex]cises #a4 ,h[ w\ld a dipp+ ne$le be ( assi/ance 9 locat+ ! magnetic poles ( ! e>?8 #b4 ,w a dipp+ ne$le weigh m be=e or aft] x is magnetiz$8 ,expla94 #c4 ,x is said t induction prec$es attraction4 ,us+ ?is idea1 expla9 h[ a magnet attracts a piece ( s(t iron4 #d4 ,devise an exp]im5t to %[ t a piece ( iron attracts a magnet j z a magnet attracts a piece ( iron4 #e4 ,give two me?ods = det]m9+ ! poles ( a magnet4 #f4 ,/ate ?ree ( ! mo/ important po9ts 9 ! !ory ( magnetism4 ,:at evid5ce supports ea*8 #g4 ,:y is a p]man5t magnet injur$ :5 x is dropp$8 #h4 ,"n two important uses ( ! e>?'s magnetic field4 #i4 ,:at magnetic pole w\ld y f9d at ! top ( an iron po/ t has /ood = "s "t 9 ! gr\nd8 ,:at pole at ! bottom8 ,h[ w\ld y te/ ?is8 ,,*apt] ,x ,,/atic ,,electricity 7#a7 ,,electrification ,,& ,,electrical ,,*>ges #bac4 ,electrical ,*>ges4--,! ideas ga9$ 9 ! /udy ( magnetism are ( assi/ance 9 ! /udy ( electricity 9 giv+ "s fundam5tal ideas & pr9ciples t w (t5 be ref]r$ to z a basis = comp>+ ! actions ( magnetiz$ & electrifi$ bodies4 ,! process ( electrify+ a body is v diff]5t f t ( magnetiz+ x4 ,?us if a rubb] comb or rod be rubb$ ) a wool5 clo? ! object rubb$ is able to attract to itself light bits ( pap]1 ?read1 etc4 ,?is peculi> attraction 0 notic$ & record$ by ! anci5t ,greeks1 #fjj ,b4,c41 :5 x 0 f\nd t amb] :5 rubb$ w\ld attract light objects to itself4 ,= a long "t x 0 suppos$ t amb] 0 ! only sub/ance %[+ ?is prop]ty4 ,dr4 ,william ,gilb]t1 h[ev]1 discov]$ t ! electrifi$ condition c\ld be produc$ by rubb+ a great v>iety ( sub/ances4 ,he nam$ ! result produc$1 electrification1 aft] ! ,greek "n = amb] 7elektron74 ,a body l h>d rubb] or amb] :i* w attract light objects :5 rubb$ is said to be electrifi$1 or to h be5 giv5 a *>ge ( electricity4 #bad4 ,law ( ,electric ,action4--,let a vulcanite rod be electrifi$ by rubb+ ) a wool5 clo? until x w attract light objects2 !n place x 9 a wire /irrup susp5d$ by a silk ?read4 ,if a second vulcanite rod is simil>ly electrifi$ & br\ght ne> ! fir/1 ! two w be f\nd to repel4 7,see ,fig4 #ahf47 ,if n[ a glass rod be rubb$ ) silk & br\ght ne> ! susp5d$ rod1 ! two w attract4 ,?is diff]5ce 9 behavior indicates a diff]5ce 9 ! electrification or *>ge ^u ! rods4 ,! two *>g$ vulcanite rods repell+ & ! *>g$ glass & vulcanite attract+ indicate ! law ( electric action4 ,l *>ges repel ea* o!r & unlike *>ges attract ea* o!r4 ,ext5sive exp]im5ts ) all k9ds ( sub/ances indicate t !re are b two k9ds ( electrical *>ges4 ,! electrical *>ge ^u glass :5 rubb$ ) silk or wool is call$ positive1 & t ^u h>d rubb] or vulcanite :5 rubb$ ) wool is call$ negative4 ,illu/ration3 ,,fig4 #ahf4--,repulsion ( l *>ges4 ,illu/ration3 ,,fig4 #ahg4--;,an alum9um foil electroscope4 ,illu/ration3 ,,fig4 #ahh4--;,a pro( plane4 #bae4 ,! ,electroscope & its ,uses4--,an electroscope is a device employ$ to te/ ! pres5ce ( an electrical *>ge4 ,! alum9um foil electroscope consi/s ( a flask clos$ by a rubb] /opp] ?r\gh :i* passes a rod :i* ends at ! top 9 a ball or plate & bel[ is atta*$ two n>r[ leaves ( ?9 alum9um-foil4 ,ord9>ily ! two leaves hang close toge!r & p>allel b if a *>g$ body is br\ght ne> ! electroscope ! leaves spread ap>t at ! bottom4 7,see ,fig4 #ahg47 ,! k9d ( *>ge ^u a body may be det]m9$ ) an electroscope z foll[s3 ,make a pro(-plane by seal+ a small metal disc on ! end ( a h>d rubb] rod4 7,see ,fig4 #ahh47 ,t\* ! disc ( ! pro(-plane fir/ to a *>g$ rubb] rod & !n to ! top ( ! electroscope4 ,! leaves ( ! latt] w sep>ate %[+ t ! electroscope is *>g$4 ,?is *>ge rema9s aft] ! pro(-plane is remov$4 ,if ! *>g$ vulcanite rod is br\ght ne> ! electroscope1 ! leaves sep>ate fur!r ,t is1 a *>ge l t on ! electroscope makes ! leaves sep>ate fur!r4 ,b if an unlike *>ge1 z t on a positively *>g$ glass rod1 is cauti\sly br\ght ne>1 ! leaves w be se5 to move toge!r4 ,illu/ration3 ,,fig4 #ahi4--,rod ) wool5 cap4 #baf4 ,two ,*>ges are ,produc$ at ! ,same ,"t4--,a closely fitt+ wool5 cov] or cap "s #c 94 long is made = ! end ( a vulcanite rod4 ,a silk ?read atta*$ to ! cap enables "o to hold ! latt] :ile ! rod is turn$ )9 x4 7,see ,fig4 #ahi47 ,if ! rod be>+ ! cap is held ne> a *>g$ electroscope little or no effect is notic$4 ,if n[ ! cap is remov$ by ! silk ?read & held ne> ! electroscope1 x w be f\nd to be positively *>g$ :ile ! rod is negatively *>g$4 ,! fact t no result is se5 :5 ! cap & rod are toge!r1 indicates t "o *>ge neutralizes ! o!r4 ,9 o!r words1 ! *>ges mu/ be equal4 ,?is illu/rates ! tru? t :5 electrification is produc$ by friction1 ! two objects rubb$ toge!r acquire equal & opposite *>ges4 #bag4 ,*>g+ by ,contact & ,conduction4--,if a small pi? ball is susp5d$ by a silk ?read1 a *>g$ rod br\ght ne> is at fir/ attract$1 b aft] contact is repell$ 7see ,fig4 #aij7 %[+ t ! ball has become *>g$ ) ! same k9d ( electrification t is ^u ! rod4 ,t is1 a *>ge giv5 to an object by contact ) a *>g$ body is ( ! same k9d z t ^u ! *>g$ "o4 ,! pro(-plane 9 ,art4 #bae c>ries ! same k9d ( *>ge t is ^u ! rod x is *>g$ f4 ,"s sub/ances h ! ability to transf] *>ges ( electrification4 ,^! are call$ conductors1 ^? t d n conduct electrification are insulators4 ,! conduct+ p[] ( a body is readily te/$ by plac+ "o end ( a rod ( ! mat]ial ^u ! top ( an electroscope & ! o!r end ^u an insulat$ support1 z 9 ,fig4 #aia4 ,if n[ a *>ge be put 9 contact ) ! body ( a1 ! electroscope w %[ by its leaves :e!r ! rod te/$ conducts or n4 ,! leaves sep>ate in/antly :5 conduct+ sub/ances are te/$1 :ile no action results ) insulators4 ,9 te/+ "s mat]ials = conductivity ! leaves are f\nd to div]ge gradually4 ,su* bodies are said to be poor conductors4 ,all degrees ( conductivity are f\nd4 ,! metals are ! be/ conductors4 ,! be/ insulators are rubb]1 mica1 %ellac1 glass1 silk1 porcela91 p>aff91 & oils4 ,illu/ration3 ,,fig4 #aij4--,! pi? ball *>g$ by contact is repell$4 ,illu/ration3 ,,fig4 #aia4--,te/+ = conductivity4 ,important ,topics #a4 ,positive & negative *anges4 ,law ( electric action4 #b4 ,electroscope & its uses4 #c4 ,conductors & insulators4 ,ex]cises #a4 ,is air a conductor8 ,give reasons = y\r answ]4 #b4 ,m5tion two po9ts ( lik5ess & two po9ts ( diff]5ce betwe5 magnetism & electrification4 #c4 ,if y 7 te/+ ! electrification ( a body ) a *>g$ pi? ball susp5d$ by a silk ?read1 w\ld attraction or repulsion be ! bett] te/8 ,give reasons4 #d4 ,h y ev] produc$ electrification by friction outside ( a laboratory8 ,expla94 #e4 ,are ! rods ^u :i* we produce electrification by friction1 conductors or insulators8 ,h[ d y expla9 ?is8 #f4 ,are conductors or insulators ( ! great] importance 9 practical electricity8 ,expla94 7#b7 ,,electric ,,fields ,,& ,,electro/atic ,,induction ,illu/ration3 ,,fig4 #aib4--;,an electric field ab\t a positively *>g$ %ell4 ,illu/ration3 ,,fig4 #aic4--;,a detector4 #bah4 ,electrical ,fields4--,9 our /udy ( magnetism we le>n$ t a magnet affects objects ab\t x by its magnetic l9es ( =ce4 ,9 a simil> way x is assum$ t a *>g$ body produces electrical effects ^u its surr\nd+s by electric l9es ( =ce4 ,= example1 ! attraction t a *>g$ body ex]ts ^u light objects ?r\gh %ort di/ances or ! influ5ce ( a *>ge ^u an electroscope sev]al feet away1 is said to be due to ! electric field ab\t ! *>g$ body4 7,see ,fig4 #aib47 ,! pres5ce ( ! electric l9es ( =ce may be %[n by plac+ a p]=at$1 sl5d]1 diamond-%ap$ piece ( tissue pap] ^u a light glass po9t] 7,fig4 #aic74 ,:5 plac$ 9 an electric field ! tissue pap] detector places itself p>allel to ! l9es ( =ce4 ,electric l9es ( =ce are said to ext5d f a positive to a negative *>ge4 7,see ,fig4 #aid47 ,! direction %[n by ! arr[ ^u ! l9es is t along :i* a small positive *>ge t5ds to move4 ,electric l9es ( =ce unlike ^? f magnets are n cont9u\s4 ,!y ext5d f a positive *>ge to a negative *>ge4 ,!re=e ea* positive *>ge is connect$ by l9es ( =ce to a negative *>ge some:]e4 ,^! ideas ( electric fields are ( mu* assi/ance 9 expla9+ _m electrical effects4 ,electrical fields betwe5 oppositely *>g$ %ells w be f\nd simil> to ,fig4 #aid1 :ile betwe5 %ells ) l *>ges1 fields are f\nd z 9 ,fig4 #aie4 ,illu/ration3 ,,fig4 #aid4--;,electric field betwe5 unlike *>ges4 ,illu/ration3 ,,fig4 #aie4--;,electric field betwe5 l *>ges4 #bai4 ,electro/atic ,induction4--,if a *>g$ body is br\ght ne> an alum9um-foil electroscope1 ! leaves sep>ate4 7,see ,fig4 #aih47 ,! ne>] ! *>ge is br\ght ! wid] ! leaves spread1 b :5 ! *>ge is remov$1 ! leaves collapse %[+ t no?+ 0 giv5 to ! electroscope4 ,x 0 simply affect$ by ! *>ge 9 its vic9ity4 ,?is production ( an electrifi$ condition 9 a body by ! influ5ce ( a *>ge ne> x is call$ electro/atic induction4 ,plac+ insulators1 su* z a %eet ( glass1 betwe5 ! *>ge & ! electroscope does n affect ! result1 :i* is app>5tly br\ght ab\t by ! action ( ! electric l9es ( =ce4 ,^! l9es ( =ce ext5d )\t difficulty ?r\gh un*>g$ insulators & t]m9ate (t5 at ! surface ( a conductor1 :]e _! influ5ce causes a *>ge to accumulate4 ,*>g$ insulators1 h[ev]1 d affect inductive action4 ,?is may be notic$ by us+ a s5sitive electroscope4 ,illu/ration3 ,,fig4 #aif4--,production ( two *>ges by ! influ5ce ( a ?ird *>ge4 ,illu/ration3 ,,fig4 #aig4--,! two *>ges sep>at$4 #bbj4 ,electrical ,sep>ation by ,induction4--,! action j describ$ may be illu/rat$ fur!r by tak+ two insulat$1 un*>g$ brass %ells1 ,a & ,b4 7,see ,fig4 #aif47 ,br+ a *>g$ vulcanite rod ne> %ell ,a :ile ! %ells are t\*+ ea* o!r4 ,!n remove %ell ,b 7,fig4 #aig7 :ile ! rod rema9s ne> ,a4 ,on te/+ ! %ells = electrification1 ,a is f\nd to possess a positive *>ge4 ,?is action is 9 "s respects simil> to magnetic induction1 = if "o places a nor?-seek+ pole ne> a piece ( iron1 ! iron develops by induction a s\?-seek+ pole at ! end ne>e/ ! magnet & a nor?-seek+ at ! o!r end4 ,!re is1 h[ev]1 "o /rik+ diff]5ce4 ,if ! magnetiz$ iron be sep>at$ into two p>ts1 ea* "p is a complete magnet possess+ two unlike poles2 :ile if ! object affect$ by electro/atic induction is sep>at$ into two p>ts "o "p has a positive *>ge & ! o!r a negative *>ge4 ,illu/ration3 ,,fig4 #aih4--;,effect ( a *>g$ rod ne> an electroscope4 ,illu/ration3 ,,fig4 #aii4--,:5 a f+] is t\*$ to ! top ( ! electroscope1 ! repell$ negative *>ge escapes4 ,illu/ration3 ,,fig4 #bjj4--,! electroscope is n[ positively *>g$4 #bba4 ,*>g+ a body by induction is easily accompli%$4 ,to *>ge an alum9um-foil electroscope by induction br+ ne> 7say #aj cm47 f ! top ( ! electroscope a *>g$ rubb] rod4 7,see ,fig4 #aih47 ,! sep>at$ leaves %[ ! pres5ce ( ! repell$ or negative *>ge1 ! positive *>ge be+ on ! disc at ! top4 ,if :ile ! *>g$ rod is held ne>1 ! metal top ( ! electroscope is t\*$ by ! f+] ! leaves at once fall toge!r %[+ t ! repell$ negative *>ge has escap$ f ! electroscope 7,fig4 #aii74 ,on remov+ fir/ ! f+] & next ! *>g$ rod1 ! positive *>ge spreads ov] ! metal p>ts ( ! electroscope1 z is %[n by ! sep>ation ( ! leaves 7,fig4 #bjj74 ,! electroscope is n[ *>g$ positively by induction4 ,if ! *>g$ rubb] rod is br\ght to ab\t #cj cm4 f ! electroscope1 its leaves t5d to move toge!r4 ,if a body *>g$ simil>ly to ! electroscope or positively1 is mov$ t[>d ! electroscope ! leaves sep>ate fur!r4 ,?is behavior ( ! electroscope enables "o to det]m9e ! k9d ( *>ge ^u a body4 ,two pr9ciples ( electro/atic induction may n[ be /at$3 7#a7 ,two equal1 unlike *>ges are always produc$ by electro/atic induction4 7#b7 ,if ! body affect$ by induction is connect$ to ! e>? by a conductor1 ! repell$ or free *>ge is conduct$ away f ! body :ile ! b\nd *>ge is held by ! induc+ *>ge4 ,^! pr9ciples apply 9 e case ( induction4 ,important ,topics #a4 ,electric l9es ( =ce4 ,*>act]i/ics 7#c74 #b4 ,electro/atic induction4 ,pr9ciples 7#b74 #c4 ,*>g+ by induction4 ,explanation4 ,ex]cises #a4 ,:at are electric l9es ( =ce8 ,:]e are !y f\nd8 ,:at does ! arr[ mean ^u ! l9es8 #b4 ,"n ?ree effects produc$ by electric fields4 #c4 ,does electro/atic induction occur outside ( laboratories8 ,:]e8 ,:58 #d4 ,giv5 a *>g$ rubb] rod1 h[ may "o *>ge f x by induction1 insulat$ brass %ells1 giv+ "s a positive & "s a negative *>ge8 #e4 ,h[ may ! *>ges ^u ! %ells be te/$8 #f4 ,9 *>g+ an electroscope by induction1 :y mu/ ! f+] be remov$ be=e ! glass rod8 #g4 ,:y is x be/ to h ! rubb] & glass rods1 us$ 9 electrification1 w>m] ?an ! air ( ! room 9 :i* ! exp]im5ts are be+ p]=m$8 #h4 ,:5 a %>p metallic po9t is held ne> ! knob ( a *>g$ electroscope ! leaves quickly come toge!r4 ,expla94 #i4 ,might "o ( ! memb]s ( y\r class 9 physics be *>g$ ) electricity1 if he %\ld /& on a bo>d support$ by dry glass insulators8 ,expla94 #aj4 ,if a metal c is *>g$ /rongly :ile /&+ on an insulator1 te/s made by means ( ! pro(-plane & electroscope %[ no *>ge on ! inside4 ,expla94 7#c7 ,,electrical ,,!ories ,,& ,,di/ribution ,,( ,,*>ges #bbb4 ,frankl9's ,!ory ( ,electricity4--,we h /udi$ ! production ( electrification by friction & induction4 ,x w be helpful n[ to consid] "s ( ! !ories ( electricity4 ,f ! ease ) :i* electrification moves1 along a conductor1 _m h imag9$ t electricity is a fluid4 ,b5jam9 ,frankl9's ,"o ,fluid ,!ory held t a positive *>ge consi/$ 9 an accumulation or an excess ( electricity :ile a negative *>ge implies a defici5cy or less ?an ! usual am\nt4 ,?is !ory l$ to repres5t+ positive electrification by a plus 77 sign & negative1 by a m9us 7-7 sign4 ,^! signs are 9 g5]al use to-day4 ,! use & significance ( ^! signs %\ld be cle>ly fix$ 9 m9d4 #bbc4 ,! ,electron ,!ory4--,v>i\s discov]ies & exp]im5ts made 9 rec5t ye>s indicate1 h[ev]1 t negative electricity consi/s ( little corpuscles or electrons :i* may pass readily f "o molecule ( a conductor to ano!r :ile _! movem5t ?r\gh an insulator is mu* ret>d$ if n entirely prev5t$4 ,?is !ory1 sometimes call$ ! ,electron ,!ory1 holds t ea* atom ( a sub/ance has z a nucleus a corpuscle ( positive electricity1 & surr\nd+ x1 m9ute negative corpuscles or electrons4 ,x is ?\ght t ! electrons 9 ! atom are v mu* small] ?an ! positive *>ges & are revolv+ ab\t ! latt] ) great rapidity4 ,ord9>ily1 ! positive & negative *>ges are equal s t ! atom is 9 a neutral or un*>g$ condition4 ,by ! action ( v>i\s =ces "s ( ! negative corpuscles )9 a conductor may be mov$ f molecule to molecule4 ,?us if a negatively *>g$ rod is br\ght ne> a conductor1 _m electrons /ream away to ! f> end *>g+ x negatively1 :ile ! ne>] end ( ! conductor is left ) few] electrons ?an usual along ) ! fix$ positive corpuscles4 ,h5ce ! ne> end is positively *>g$4 7,see ,fig4 #aih47 ,on ! o!r h&1 if a positive *>ge is us$1 x attracts ! electrons f ! f> end1 leav+ ! immovable positive corpuscles !re1 & t end becomes positively electrifi$1 :ile ! ne>] end ) its surplus ( electrons is1 ( c\rse1 negatively electrifi$4 ,! ,electron ,!ory is consid]$ well f\nd$ s9ce ! electrons h 7a7 _h _! mass det]m9$1 7b7 _! spe$ measur$1 7c7 _! electric *>ge det]m9$1 7d7 & _! behavior :ile pass+ ?r\gh magnetic & electric fields obs]v$4 ,^! facts & o!r exp]im5tal evid5ce h demon/rat$ ! exi/5ce ( electrons4 ,! positive corpuscle has n be5 directly obs]v$ b is assum$ to exi/ to acc\nt = ! effects obs]v$ 9 induction1 *>g+ by friction1 etc4 #bbd4 ,di/ribution ( an ,electric ,*>ge ^u a ,conductor4--,we h appli$ ! electron !ory 9 expla9+ ! ph5om5on ( electro/atic induction4 ,let u n[ use x 9 /udy+ ! di/ribution ( an electric *>ge ^u a conductor4 ,let a cyl9drical metal vessel op5 at ! top & insulat$ by be+ plac$ ^u pieces ( seal+ wax h a *>ge ( negative electricity giv5 x4 7,see ,fig4 #bja47 ,on n[ tak+ a pro( plane & attempt+ to obta9 a *>ge f ! int]ior ( ! vessel no result is f\nd1 :ile a *>ge is readily obta9$ f ! outside ( ! di%4 ,?is result is expla9$ by consid]+ t ! electrons are mutually self-repell5t & 9 _! attempt to sep>ate z widely z possible pass to ! out] surface ( ! vessel4 ,?is same condition is also true ( a di% made ( wov5 wire4 ,if ! *>g$ conductor is n sph]ical 9 outl9e1 an unev5 di/ribution ( ! *>ge is obs]v$4 ,?us if an egg-%ap$ conductor is insulat$ & *>g$ 7see ,fig4 #bjb71 a pro( plane t\*$ to ! broad end ( ! body & !n to an electroscope causes a c]ta9 div]g5ce ( ! leaves ( ! latt]4 ,if n[ a *>ge be tak5 f ! po9t$ end by ! pro( plane to ! un*>g$ electroscope1 a great] spread+ ( ! leaves ?an be=e w be notic$4 ,?is indicates t ! electricity may be unev5ly di/ribut$ ov] ! surface ( a body4 ,x is f\nd t ! electric d5sity1 z x is call$1 is greate/ :]e ! surface curves mo/ %>ply4 ,at a v %>p curve1 z at a po9t1 ! electric d5sity may be s great t a "p ( ! *>ge escapes into ! air4 7,see ,fig4 #bjc47 ,= ?is reason electric conductors on :i* x is desir$ to keep an electric *>ge h r\nd surfaces & all %>p po9ts & corn]s are avoid$4 ,:ile conductors1 su* z lightn+ rods1 :i* are design$ to facilitate ! escape ( electric *>ges1 are provid$ ) a numb] ( %>p po9ts at ! end or else:]e4 ,at su* po9ts1 air p>ticles are drawn =cibly aga9/ ! po9t & aft] be+ *>g$ are driv5 away /rongly1 creat+ ! s-call$ electrical w9d :i* c>ries away ! *>ge at a rapid rate4 7,see ,fig4 #bjc47 ,illu/ration3 ,,fig4 #bja4--,no *>ge is f\nd inside a holl[ vessel4 ,illu/ration3 ,,fig4 #bjb4--,m *>ge at ! po9t$ end4 #bbe4 ,lightn+ & ,electricity4--,! fact t lightn+ is an electrical dis*>ge 0 fir/ %[n 9 #ageb by ,b5jam9 ,frankl91 :o drew electric *>ges f a cl\d by fly+ a kite 9 a ?und]/orm4 ,) ! electricity :i* pass$ d[n ! kite /r+ he p]=m$ a numb] ( electrical exp]im5ts4 ,?is discov]y made ,frankl9 fam\s among sci5tific m5 ev]y:]e4 ,frankl9 !n sugge/$ ! use ( lightn+ rods to protect build+s f lightn+4 ,^! rods act z conductors = ! electric dis*>ge & ?us prev5t x f pass+ ?r\gh ! build+1 ) ! risk ( ov]heat+ "s "p & sett+ ! latt] on fire4 ,! po9ts provid$ at ! top ( lightn+ rods are believ$ to aid 9 prev5t+ /rokes ( lightn+ by ! sil5t dis*>ge ( ! s-call$ electric w9d :i* t5ds to quietly unite ! *>ges 9 ! cl\ds & on ! e>? b5ea?4 ,illu/ration3 ,,fig4 #bjc4--;,electrical w9d produc$ by a po9t$ conductor4 ,illu/ration3 ,,fig4 #bjd4--;,electrical :irl4 ,! reaction f ! electrical w9d causes x to revolve4 ,illu/ration3 ,,fig #bje4 ,! wire scre5 protects ! electroscope4 ,! *>ge 9 an electrifi$ cl\d acts inductively ^u ! e>? b5ea?1 attract+ an opposite *>ge to ! objects bel[4 ,! dis*>ge f ! cl\d (t5 passes to ! objects b5ea?1 su* z trees or build+s4 ,?und] is believ$ to be due to ! sudd5 expansion ( ! air :5 int5sely heat$ by ! electric dis*>ge & its sudd5 contraction1 l a slap1 z ! track in/antly cools4 ,?und] at a di/ance is usually foll[$ by rumbl+s due to *anges 9 ! int5sity ( ! s\nd ma9ly due to reflections ( s\nd waves f cl\ds & o!r reflect+ surfaces4 #bbf4 ,an electric scre5 is a device = cutt+ (f ! influ5ce ( an electric *>ge4 ,f>aday f\nd t if a s5sitive electroscope is surr\nd$ by a wire me% scre5 7see ,fig4 #bje71 no evid5ce ( electrification c\ld be f\nd inside4 ,9 o!r words1 a network ( conductors on a build+ makes ! be/ protection aga9/ lightn+1 provid$ x is connect$ to ! e>? by good conductors at sev]al places4 ,important ,topics #a4 ,electrical !ories4 ,evid5ces = electron !ory4 #b4 ,h[ is ! !ory us$ 9 expla9+ induction8 #c4 ,*>ges1 & di/ribution on conductors 7effect ( %ape74 #d4 ,lightn+3 cause1 effects1 lightn+ rods4 ,ex]cises #a4 ,9 :at respects is ,frankl9's "o-fluid !ory l ! electron !ory8 ,9 :at respects diff]5t8 #b4 ,consid] two %ells *>g$ by induction f an electrifi$ rubb] rod1 "o positively & "o negatively4 ,expla9 ! process1 us+ ! ideas ( ! electron !ory4 #c4 ,%\ld ! metal top ( an electroscope h %>p corn]s8 ,expla94 #d4 ,w\ld a tall /eel t[] h ! same ne$ ( a lightn+ rod z a brick *imney ( ! same height8 ,expla94 #e4 ,w a solid sph]e hold a great] *>ge ( electricity ?an a holl[ "o ( ! same diamet]8 ,expla94 #f4 ,if a positively *>g$ cl\d floats ov] a tree :i* is a good conductor ( electricity w ! tree be *>g$8 ,%[ diagram4 ,expla94 7#d7 ,,pot5tial1 ,,capacity ,,& ,,! ,,electric ,,cond5s] #bbg4 ,conditions ,caus+ a ,movem5t ( ,electricity4--,9 ! /udy ( conductors & insulators x 0 obs]v$ t an electric *>ge mov$ along ! conduct+ rod to ! electroscope4 ,?is movem5t ( electricity along a conductor is a result ( great practical importance4 ,we w n[ consid] ! conditions t produce ! fl[ or curr5t ( electricity4 ,let two electroscopes /& ne> ea* o!r4 ,*>ge "o1 ,c 7,fig4 #bjf71 /rongly & *>ge ! o!r slightly4 ,if n[ a light /iff wire atta*$ to a /ick ( seal+ wax be plac$ s z to connect ! tops ( ! electroscopes1 ! leaves ( ,c w p>tly close :ile ^? ( ,d w op5 slightly1 ?us indicat+ a movem5t ( electricity f ,c to ,d along ! wire4 ,! movem5t 0 f a place ( great] degree ( electrification to "o ( less4 ,illu/ration3 ,,fig4 #bjf4--;,electricity fl[s f high to l[ pot5tial4 #bbh4 ,pot5tial4--,! pot5tial ( an electrifi$ body is its degree ( electrification4 ,!re=e1 x is said t electroscope ,c m5tion$ above has a great] pot5tial ?an electroscope ,d4 ,! movem5t ( electricity is f a place ( great] or high pot5tial to "o ( less] or l[ pot5tial4 ,if two bodies are at ! same pot5tial !re w be f\nd no movem5t ( electricity betwe5 !m4 ,a diff]5ce ( pot5tial betwe5 two po9ts connect$ by a conductor is !re=e ! necess>y condition = an electric curr5t4 ,j z heat is transmitt$ along a conductor f a place ( high to "o ( l[] temp]ature1 s electricity is transmitt$ along a conductor f a place ( high to "o ( l[ pot5tial4 ,?us pot5tial 9 electricity corresponds to temp]ature 9 heat4 ,"o is ! degree ( electrification1 ! o!r1 ! degree ( hotness4 ,illu/ration3 ,,fig4 #bjg4--;,air pressure app>atus to illu/rate electrical pressure4 #bbi4 ,electrical pressure is a t]m sometimes us$ = diff]5ce ( pot5tial4 ,to bett] und]/& electrical pressure consid] ?ree r\nd tanks 7,fig4 #bjg7 conta9+ air4 ,a is a tank hold+ air at #aj lbs4 pressure p] squ>e in*1 above atmosph]ic pressure1 ,b is op5 to ! air & h5ce is at atmosph]ic pressure :ile ,c has a p>tial vacuum1 ) #aj lbs4 less pressure ?an t ( ! atmosph]e4 ,if ! valve at ,d or ,e is op5$ a fl[ ( air sets up until ! pressures are equaliz$4 ,:ile if ! pump at ,p is work+ a diff]5ce 9 pressure is easily ma9ta9$4 ,tank ,a corresponds to an insulat$ body *>g$ to a high positive pot5tial2 tank ,b1 op5 to ! air1 a body connect$ to ! e>?2 :ile tank ,c repres5ts a body hav+ a negative pot5tial4 ,! e>? is said to h z]o pot5tial4 ,n[ j z compress$ air w be pu%$ into ! atmosph]e 7z f ,a to ,b7 :ile air at atmosph]ic pressure w if possible be =c$ itself into a p>tial vacuum 7z f ,b to ,c71 s electricity at a positive pot5tial w t5d to move to a place at z]o pot5tial1 :ile t at z]o pot5tial t5ds to move to a place ( negative pot5tial4 ,bodies at ! same pot5tial z ! e>?1 or at z]o pot5tial1 are also said to be neutral4 ,^? positively electrifi$ h a positive pot5tial1 ^? negatively electrifi$ h a negative pot5tial4 ,z 9 gases1 movem5t always t5ds f high] pressure 7pot5tial7 to l[] pressure 7pot5tial74 ,illu/ration3 ,,fig4 #bjh4--,! metal plate gives ! electroscope a great] surface & h5ce great] capacity4 #bcj4 ,capacity4--,if we h a #ajj-;gallon tank & a #aj-;gallon tank connect$ by a pipe bo? fill$ ) compress$ air1 ! l>g] tank w conta9 t5 times z mu* air z ! small] at ! same pressure s9ce x has t5 times ! capacity1 or1 if ! two tanks are sep>at$ & ! same am\nt ( air is conta9$ 9 ea*1 ! pressure ( ! air conta9$ 9 ! small tank w be t5 times t 9 ! l>ge "o4 ,! electrical capacity ( a conductor is 9 "s respects simil> to ! capacity ( a tank = air4 ,s9ce1 h[ev]1 electrical *>ges are ^u ! surface ( a body1 its capacity dep5ds 9 "p ^u ! ext5t ( surface4 ,= example1 if a *>ge is tak5 f a *>g$ rubb] rod by a pro( plane to an electroscope a c]ta9 div]g5ce ( ! leaves w be notic$4 ,if a circul> metal plate sev]al times ! diamet] ( ! top ( ! electroscope is laid ^u ! latt] 7see ,fig4 #bjh71 & a *>ge equal to t us$ be=e is br\ght to ! electroscope1 ! leaves %[ less div]g5ce ?an be=e1 %[+ t ! same *>ge gives a l[] pot5tial :5 plac$ ^u a body ( great] capacity4 ,illu/ration3 ,,fig4 #bji4--;,a plate cond5s]4 ,illu/ration3 ,,fig4 #baj4--;,a cond5s] ( sev]al plates4 #bca4 ,! electric cond5s] is a device hav+ a l>ge electrical capacity consi/+ ( p>allel conductors sep>at$ by good insulators4 ,x has be5 devis$ to enable "o to obta9 a l>ge electrical *>ge ^u a body ( conv5i5t size4 ,su* an app>atus is ( great practical value 9 _m exp]im5ts & op]ations4 ,its con/ruction involves ! pr9ciple ( electro/atic induction 9 :i* a *>ge ( "o k9d attracts & holds /rongly a *>ge ( opposite k9d ne> x4 ,9 its simple/ =m x consi/s ( two p>allel conductors sep>at$ f ea* o!r 7,fig4 #bji74 ,! upp] plate has be5 *>g$ negatively4 ,?is has giv5 ! l[] plate a positive *>ge by induction1 s9ce ! latt] is connect$ to ! e>?4 ,^! positive & negative *>ges hold or b9d ea* o!r s t a l>ge quantity may be accumulat$4 ,to increase ! capacity ( a cond5s]1 sev]al plates are us$ connect$ z 9 ,fig4 #baj4 ,x is a curi\s fact t ! k9d ( insulator betwe5 ! *>g$ conductors ( a cond5s] affects its capacity4 ,?us if glass1 p>aff9e1 or beeswax is betwe5 ! plates in/ead ( air1 ! plates w hold m electricity at ! same pot5tial4 ,= ?is reason cond5s] plates are (t5 sep>at$ by %eets ( glass1 p>aff9$ pap]1 or mica4 ,illu/ration3 ,,fig4 #baa4--;,a ,leyd5 j> & a dis*>g]4 #bcb4 ,! ,leyd5 ,j>4--,a conv5i5t =m ( cond5s]1 us$ z long ago z #agde1 is ! ,leyd5 j>4 ,x consi/s ( a glass j> 7,fig4 #baa7 coat$ "p way up1 inside & out1 ) t9foil4 ,! inn] coat+ is connect$ by a *a9 to a knob at ! top4 ,! ,leyd5 j> is *>g$ by connect+ ! out] coat+ to ! e>? :ile to ! inn] coat+ is giv5 a *>ge ( ei!r k9d ( electricity4 ,! o!r k9d ( *>ge is develop$ by induction ^u ! out] coat+1 & ea* *>ge b9ds ! o!r4 ,to dis*>ge a j>1 a conductor1 z a wire1 is connect$ fir/ to ! out] coat+ & held !re :ile ! o!r end is br\ght to ! knob at ! top4 ,a bright sp>k is produc$ :5 ! two *>ges comb9e4 ,x is be/ n to let ! dis*>ge f ! j> pass ?r\gh ! body unless "o is c]ta9 t only a v small *>ge is pres5t4 #bcc4 ,oscillatory ,dis*>ge4--,! dis*>ge f a ,leyd5 j> is an int]e/+ ph5om5on4 ,! ru% ( electricity f "o coat to ! o!r does n /op :5 ! two coats are exactly neutraliz$ b cont9ues until ! two plates are *>g$ j oppositely to _! condition at fir/1 !n a ru% ( electricity 9 ! opposite direction occurs4 ,?is alt]nation cont9ues sev]al times & con/itutes :at is call$ ! oscillatory dis*>ge4 7,see ,fig4 #dad47 ,?is oscillatory dis*>ge sets up waves 9 ! e!r4 ,^! are call$ ,h]tzian waves 9 honor ( _! discov]]1 ,he9ri* ,h]tz4 ,!y are ! e!r waves us$ 9 wireless telegraphy4 ,a lightn+ fla% has be5 %[n by photographs & by o!r means to be oscillatory4 ,?is fact supports ! idea t ! electrical conditions j prec$+ ! /roke ( lightn+ reproduce a cond5s] on a l>ge scale4 ,! *>g$ cl\d is ! upp] *>g$ plate1 ! e>? b5ea?1 *>g$ by induction f ! cl\d1 is ! l[] *>g$ plate1 :ile ! air betwe5 is ! insulator or dielectric z x is sometimes call$4 ,important ,topics #a4 ,pot5tial3 high1 l[1 z]o1 positive1 negative1 simil> to temp]ature & air pressure4 #b4 ,capacity affect$ by 7#a7 area1 7#b7 induction4 #c4 ,cond5s]s1 ,leyd5 j>1 p>allel plate4 #d4 ,oscillatory dis*>ge1 conditions1 results4 ,ex]cises #a4 ,is ! air a conductor8 ,expla94 #b4 ,c ! ,leyd5 j> be /rongly *>g$ if ! out] coat is insulat$8 ,expla94 #c4 ,^u :at two conditions does ! capacity ( a body dep5d8 ,h[ 9 ea* case8 #d4 ,w\ld a lightn+ dis*>ge produce wireless waves8 ,expla94 #e4 ,if a %>p tack be dropp$ po9t up on ! plate ( an electroscope ! latt] is quickly dis*>g$4 ,expla94 7#e7 ,,electro/atic ,,g5]ators #bcd4 ,/atic ,electric ,ma*9es4--,_m ma*9es h be5 inv5t$ to produce l>g] quantities ( /atic electricity ?an we h us$ 9 ! exp]im5ts previ\sly describ$4 ,"o ( ! e>li] ( ^! 0 ! plate friction ma*9e 9 :i* a l>ge circul> glass plate 0 rotat$ :ile a pad ( "s mat]ial 0 held aga9/ x4 ,?is ma*9e 0 capable ( produc+ p[]ful effects1 b x took mu* "w to turn x1 & x has be5 ab&on$ = a m effici5t device1 ! /atic induction ma*9e4 #bce4 ,! electrophorus is ! simple/ /atic induction g5]ator1 consi/+ simply ( a flat circul> plate ( "s insulat+ mat]ial1 z p>aff9e1 %ellac1 or ros9 conta9$ 9 a metal pan1 & a flat circul> metal disc hav+ an insulat+ h&le4 ,illu/ration3 ,,fig4 #bab4--;,an electrophorus4 ,! electrophorus is us$ z foll[s3 ,! plate is fir/ electrifi$ by rubb+ or beat+ ) fur or a wool5 clo?4 ,! plate w be f\nd to be *>g$ negatively4 ,! metal disc is plac$ ^u ! plate by hold+ ! insulat+ h&le4 ,! upp] surface ( ! *>g$ body is slightly unev5 s t ! disc t\*es b a few high po9ts4 ,! great] "p ( ! *>g$ surface is sep>at$ f ! metal disc by air1 a good insulator4 ,! *>ge !re=e acts inductively ^u ! disc repell+ negative electricity to ! upp] surface ( ! disc1 leav+ ! l[] surface *>g$ positively 7,fig4 #bab74 ,if n[ ! f+] is t\*$ to ! disc ! repell$ negative *>ge escapes & ! :ole disc is left positively *>g$4 ,! disc is n[ remov$ 7,fig4 #bac7 & ! *>ge ^u x may be te/$ or us$ 9 any desir$ mann]4 ,! disc may be re*>g$ _m times )\t rubb+ ! plate aga94 ,illu/ration3 ,,fig4 #bac4--;,electrophorus *>g$4 ,^! electrical *>ges possess en]gy4 ,:at is ! s\rce ( ?is en]gy8 ,! answ] may be det]m9$ by ! foll[+ exp]im5t4 ,place ! disc ^u ! *>g$ plate4 ,t\* ! disc ) ! f+] to remove ! repell$ *>ge4 ,connect an electroscope to ! disc by a f9e wire4 ,no?+ appe>s on ! electroscope1 s9ce ! disc has be5 connect$ to ! e>?1 & is !re=e at z]o pot5tial4 ,if n[ ! disc is lift$ sl[ly1 ! leaves ( ! electroscope gradually sep>ate1 %[+ t a *>ge ( electricity appe>s :5 ! disc is be+ lift$ aga9/ ! =ce ( attraction betwe5 ! two *>ges4 ,j z pot5tial en]gy is develop$ 9 a weight :5 x is lift$ aga9/ ! e>?'s attraction s electrical en]gy appe>s 9 ! disc :ile x is be+ sep>at$ f ! plate4 ,! electrical en]gy ( ! *>ge is !re=e due to ! "w done 9 sep>at+ ! two *>ges4 ,?is electrical en]gy appe>s z heat & light1 :5 ! disc is dis*>g$4 ,x may be employ$ to ignite gas1 gunp[d]1 etc4 #bcf4 ,! ,toepl]-,holtz ,induction ,ma*9e4--,?is is a type ( induction or influ5ce ma*9e t is (t5 us$ = produc+ a cont9u\s supply ( electricity z 9 ! op]ation ( ,x ray ma*9es1 9 lecture demon/rations1 etc4 ,?is ma*9e 7,fig4 #bad7 consi/s ( two discs3 "o fix$1 ! o!r m\nt$ s z to revolve4 ,^u ! back ( ! fix$ plate are two sectors ( t9foil :i* become *>g$ oppositely4 ,^u ! revolv+ plate are six metallic discs4 ,^! discs act l ! discs ( ! electrophorus4 ,!y become *>g$ by induction f ! *>ges ^u ! sectors fa/5$ to ! fix$ plate4 ,! bru%es held by a rod t\* ! discs at j ! "r "t to take (f ! repell$ *>ge4 ,! *>ges induc$ ^u ! discs are tak5 (f by two metal combs ^: po9ts are held close to ! revolv+ disc4 ,! ,leyd5 j>s assi/ 9 accumulat+ a good /rong *>ge be=e a sp>k passes betwe5 ! t]m9al knobs4 ,"s ma*9es are built up ( sev]al pairs ( plates & give correspond+ly l>ge am\nts ( electricity4 ,illu/ration3 ,,fig4 #bad4--,! ,toepl]-,holtz induction ma*9e4 ,important ,topics ,/atic ,electric ,g5]ators4--7a7 plate friction ma*9e1 7b7 electrophorus1 7c7 induction or influ5ce ma*9e4 ,ex]cises #a4 ,pot5tial is simil> to :at o!r t]ms t we h /udi$8 #b4 ,:at ?ree electrical ph5om5a are bett] und]/ood f a /udy ( ! l9es ( =ce8 #c4 ,h[ _m *>ges may be produc$ by an electrophorus be=e ! plate ne$s to be electrifi$ aga98 ,expla94 #d4 ,! /atic induction ma*9e is (t5 call$ a cont9u\s electrophor\s4 ,:y8 #e4 ,! ,leyd5 j>s us$ ) ! induction ma*9e cause mu* bright] sp>ks to be produc$ ?an )\t !m4 ,expla94 #f4 ,) ! ,leyd5 j>s remov$1 w\ld ! frequ5cy ) :i* ! sp>ks pass betwe5 ! knobs be increas$ or decreas$8 ,expla94 #g4 ,m5tion ?ree lik5esses & ?ree diff]5ces betwe5 magnetism & /atic electricity4 #h4 ,w y receive a great] %ock by t\*+ a knob ( a *>g$ ,leyd5 j> :5 x is held 9 ! h& or :5 x is /&+ on a %eet ( glass8 ,expla94 #i4 ,9 :at way may an electric *>ge be divid$ into ?ree equal p>ts8 ,review ,outl9e3 ,magnetism & ,/atic ,electricity ,comp>ison betwe5 ,magnetism & ,/atic ,electricity4 ,sub/ances are3 magnetic1 conductors1 non-magnetic4 insulators4 ,produc$ by3 induction4 friction1 or induction4 ,!ory3 molecul>4 electron4 7fluid7 attraction1 attraction1 ,fields ( ,=ce repulsion1 repulsion1 ,expla93 induction1 induction4 action ( compass4 magnetoscope1 dip1 electroscope1 electron1 decl9ation1 pole1 positive1 negative1 ret5tivity1 pot5tial1 capacity1 ,t]ms3 p]meability1 cond5s]1 electrophorus1 lode/one1 oscillatory dis*>ge1 magnetic m]idian4 lightn+4 ,lik5ess3 a--produc$ by induction1 b--attract bo? are3 & repel1 c--h fields ( =ce4 a--electricity c be conduct$1 magnetism _c4 ,diff]5ces3 b--electricity 9 all sub/ances1 magnetism 9 few4 c--magnetism ) ! compass indicates direction4 ,,*apt] ,,xi ,,curr5t ,,electricity 7#a7 ,,electrical ,,curr5ts ,,& ,,circuits #bcg4 ,s\rces ( ,electric ,curr5ts4--,9 /udy+ ! production & di/ribution ( /atic electricity x 0 se5 t if two bodies at diff]5t pot5tials are connect$ by a copp] wire a movem5t ( electricity to ! body hav+ ! l[] pot5tial occurr$ along ! conduct+ wire4 ,?is movem5t ( electricity is call$ an electric curr5t 7,art4 #bbg74 ,a diff]5ce ( pot5tial is !re=e (t5 call$ an electromotive =ce 7,e4,m4,f471 s9ce x produces ! movem5t ( electricity 9 a conductor4 ,! curr5t betwe5 two oppositely *>g$ bodies la/s = s %ort a "t z to be ( little or no practical value unless "s means are f\nd = cont9ually re*>g+ ! bodies4 ,t is1 "s device mu/ be us$ to re/ore ! diff]5ce 9 pot5tial z fa/ z ! conduct+ wire equalizes x4 ,! cont9ual *>g+ ( ! bodies takes "w4 ,9 o!r words1 x requires a cont9ual exp5diture ( "s =m ( en]gy 7:i* is conv]t$ into electrical en]gy7 to produce ! electric curr5t4 ,two =ms ( en]gy are commonly us$ = ?is purpose4 7,a7 ,*emical en]gy is employ$ 9 voltaic cells = produc+ electric curr5ts4 7,b7 ,me*anical en]gy is us$ = ! same purpose 9 ! dynamo & simil> devices4 #bch4 ,! voltaic cell is nam$ aft] ,volta1 an ,italian physici/1 :o 9 #ahjj inv5t$ x4 ,9 its simple/ =m x consi/s ( a /rip ( copp] & a /rip ( z9c plac$ 9 dilute sulphuric acid 7"o "p acid to fifte5 or tw5ty ( wat]7 7,fig4 #bae74 ,by ! use ( s5sitive app>atus1 x c be %[n t ! copp] plate ( ! voltaic cell has a positive *>ge & ! z9c plate a negative *>ge4 ,= example1 let a flat plate #aj cm4 9 diamet] be plac$ ^u ! knob ( an electroscope & a simil> plate1 coat$ ) %ellac & provid$ ) an insulat+ h&le1 be set ^u x to =m a cond5s]4 7,see ,fig4 #baf47 ,if n[ wires f ! two plates ( a simple voltaic cell be respectively connect$ to ! plates ( ! cond5s]1 *>ges f ! copp] & z9c plates w accumulate ^u ! two cond5s] plates4 ,n[ remove ! wires & lift ! upp] plate4 ,! b\nd *>ge ^u ! l[] plate w spread ov] ! leaves & cause !m to sep>ate4 ,^u te/+1 ! *>ge f ! z9c plate w be f\nd to be negative & t f ! copp] plate1 positive4 ,s9ce a positive *>ge is f\nd ^u ! copp] plate x is call$ ! positive electrode2 ! z9c plate is call$ ! negative electrode4 ,illu/ration3 ,,fig4 #bae4--;,cross-section ( a simple voltaic cell4 ,illu/ration3 ,,fig4 #baf4--,te/+ ! *>ges ^u ! plates ( a simple voltaic cell4 #bci4 ,te/ = an ,electric ,curr5t4--,if ! copp] & z9c plates ( a voltaic cell are connect$ by a wire1 a curr5t ( electricity is set up 9 ! conductor4 ,evid5ce ( ! curr5t may be obta9$ by hold+ ! conduct+ wire ov] & p>allel to ! ne$le ( a magnetoscope4 ,! ne$le is deflect$ by ! action ( ! curr5t p>allel to x 7,fig4 #bag74 ,?is magnetic effect ( a curr5t is ! means usually employ$ = ! detection & measurem5t ( an electric curr5t4 ,su* a device :i* detects an electric curr5t by its magnetic effect is call$ a galvanoscope1 9 honor ( ,galvani1 :o 9 #aghf 0 ! fir/ to discov] h[ to produce an electric curr5t4 ,illu/ration3 ,,fig4 #bag4--,! magnetic ne$le is deflect$ by ! curr5t4 ,illu/ration3 ,,fig4 #bah4--;,diagram ( an electric bell circuit4 #bdj4 ,! ,electric ,circuit4--,! entire conduct+ pa? along :i* a curr5t ( electricity fl[s is call$ an electric circuit4 ,9 ! case ( a voltaic cell1 ! circuit includes n only ! wires connect+ ! plates b also ! plates !mselves & ! liquid betwe5 !m4 ,:5 "s device or app>atus is to receive curr5t f ! cell1 x is atta*$ to ! plates & wires s t ! device is a "p ( ! electric circuit4 ,sep>at+ ! circuit at any po9t is call$ break+ or op5+ ! circuit1 :ile connect+ ! ends ( an op5 circuit is call$ mak+ or clos+ ! circuit4 ,a device = op5+ & clos+ a circuit is call$ a key or swit*4 ,! electric circuit us$ 9 r++ a door bell is famili> to mo/ boys & girls4 ,?is circuit is op5 mo/ ( ! "t4 ,x is clos$ by press+ ! pu%-button at ! door1 & ! fl[ ( curr5t ?r\gh ! electric bell causes ! latt] to r+4 ,su* a circuit is repres5t$ 9 ,fig4 #bah4 ,"h ,c is ! voltaic cell1 ! two l9es repres5t+ ! plates ( ! cell4 ,a cross-section view ( ! pu%-button 7,p71 %[s h[ ! circuit is clos$1 7,b7 is ! bell4 ,:]ev] curr5t electricity is us$ ! device 9 :i* x is employ$ =ms a "p ( an electric circuit ext5d+ back to "s electric g5]ator4 ,?is g5]ator mu/ be able to cont9ually produce an ,e4,m4,f41 or a diff]5ce ( pot5tial betwe5 its t]m9als1 9 ord] t ! movem5t ( electricity may be cont9u\s4 ,important ,topics 7a7 ,electric g5]ators3 7#a7 voltaic cell uses *emical en]gy2 7#b7 dynamo uses me*anical en]gy4 7b7 ,electric circuits3 7#a7 op51 7#b7 clos$1 7#c7 key & swit*4 7c7 ,voltaic & galvanic electricity 7names74 7d7 ,galvanoscope1 uses4 ,ex]cises #a4 ,9 :at two ways are /atic & curr5t electricity alike8 ,9 :at two diff]5t8 #b4 ,draw a diagram ( an electric bell circuit at y\r home4 ,give ! location ( ! electric bell1 ! electric g5]ator & ! pu%-button4 ,%[ ! connect+ wires1 & expla9 briefly h[ ! circuit is op]at$4 #c4 ,repres5t "s o!r electric circuit1 nam+ ! g5]ator & o!r devices 9 ! circuit4 #d4 ,look up ! "w ( ,volta & ,galvani & write a /atem5t ( ! electrical discov]ies & inv5tions made by !m4 7#b7 ,,! ,,voltaic ,,cell ,,& ,,its ,,action #bda4 ,! simple voltaic cell consi/s ( a /rip ( copp] & a /rip ( z9c plac$ 9 dilute sulphuric acid4 7,see ,fig4 #bai47 ,a %ort "t aft] plac+ ! plates 9 ! acid1 bubbles ( a gas 7hydrog57 appe> on ! surface ( ! z9c4 ,^! bubbles increase 9 size & "s rise to ! surface ( ! liquid4 ,no?+ appe>s ^u ! copp] plate4 ,if ! tops ( ! plates are connect$ by a wire1 an electric curr5t is set up ?r\gh ! wire & ! cell1 & bubbles ( gas also appe> ^u ! copp] z well z on ! z9c4 ,9 a %ort "t ! surface ( ! copp] becomes coat$ ) bubbles & ! curr5t becomes mu* weak]4 ,if ! plates are left 9 ! acid = "s "t ! z9c is f\nd to be eat5 away1 hav+ be5 dissolv$ 9 ! acid ?r\gh *emical action4 ,! copp]1 h[ev]1 rema9s practically unaffect$4 ,illu/ration3 ,,fig4 #bai4--;,a simple voltaic cell4 #bdb4 ,h[ ! ,curr5t is ,produc$4--,to ma9ta9 ! electric curr5t a cont9ual supply ( en]gy is requir$4 ,?is is furni%$ by ! *emical action ( ! acid ^u ! z9c4 ,! *emical action is 9 sev]al respects l combu/ion or burn+1 by means ( :i* *emical en]gy is trans=m$ into heat en]gy4 ,9 ! voltaic cell ! *emical action ( ! acid ^u ! z9c trans=ms *emical en]gy into electrical en]gy4 ,! ,e4,m4,f4 or diff]5ce ( pot5tial may be consid]$ z orig9at+ at ! surface ( ! z9c :]e ! *emical action takes place4 ,at ?is po9t ! z9c has ! l[] & ! liquid 9 contact ) x ! high] pot5tial4 ,! molecules ( ! acid are believ$ to be sep>at$ or brok5 up into two p>ts call$ ions2 "o ion1 ! ,,s#d or sulphion1 comb9es ) ! z9c =m+ z9c sulphate1 ! o!r1 or hydrog5 7,h7 ion1 passes ov] to ! copp] plate1 & accumulates on ! surface ( ?is plate giv+ x a positive *>ge4 ,x is !re=e call$ ! positive ion4 ,! sulphion ion1 or ,,s#d ion1 c>ries a negative *>ge to ! z9c4 ,x is !re=e call$ ! negative ion4 #bdc4 ,! ,direction ( ! ,curr5t4,k--,beg9n+ at ! surface ( ! z9c ! direction ( ! movem5t ( positive electricity may be trac$ ?r\gh ! liquid to ! copp] plate1 to ! wire1 to ! z9c plate1 to ! />t+ po9t1 ?us complet+ ! electric circuit4 ,:5 ! circuit is clos$ x is f\nd t ! movem5t ( electricity />ts 9 all p>ts ( ! circuit at practically ! same in/ant4 ,k ,_m sci5ti/s consid] t curr5t 9 a conductor consi/s ( negative electrons fl[+ 9 a direction opposite to t describ$ 9 ,art4 #bdc4 ,?is is call$ ! electron curr5t1 z di/+ui%$ f ! electric curr5t describ$ above4 ,illu/ration3 ,,fig4 #bbj4--;,a comp>ison ( a voltaic cell & circuit to a wat] pump & connect+ pipes4 #bdd4 ,! production ( ! curr5t may be illu/rat$ by describ+ a device = produc+ a cont9u\s circulation ( wat]4 ,?us let ,cu & ,zn repres5t two pipes connect$ by two horizontal tubes1 "o at ,v provid$ ) a valve & "o at ,p ) a rot>y ,pump4 7,see ,fig4 #bbj47 ,suppose ! pipes fill$ to ! level ( ,v & ! pump />t$4 ,! pump w =ce wat] f ,zn to ,cu1 ?r\gh ,p1 ! level fall+ 9 ,zn & ris+ 9 ,cu4 ,if ! valve ,v is op5 ! wat] w fl[ back ?r\gh ,v z long z ! pump is work+4 ,if ,v is clos$1 ! level 9 ,cu w rise z high z ! driv+ =ce ( ! pump c s5d x4 ,if n[ ,v is op5$1 ! pump w ma9ta9 ! wat] 9 circulation f ,cu to ,zn ?r\gh ,v4 ,9 ! illu/ration1 ! tubes ,cu & ,zn correspond to ! conduct+ plates ( copp] & z9c ( a voltaic cell4 ,! pump ,p repres5ts ! *emical action :i* produces ! electrical pressure4 ,! upp] pipe repres5ts ! "p ( ! circuit outside ( ! cell1 ! valve ,v corresponds to an electric key or swit* :i* is us$ to op5 & close ! electric circuit4 #bde4 ,pol>ization4--,9 ! simple voltaic cell1 aft] ! circuit is clos$1 bubbles ( hydrog5 collect ^u ! copp] plate4 ,?is accumulation ( hydrog5 gas is call$ pol>ization4 ,x acts z a non-conduct+ lay] ^u ! surface ( ! plate & s]i\sly int]f]es ) ! movem5t ( electricity f ! liquid to ! copp] plate n only 9 ! simple voltaic cell b 9 _m o!rs z well4 ,"s voltaic cells are made entirely free f ?is defect1 ei!r 7a7 by ! removal ( ! hydrog5 z fa/ z x is =m$1 or 7b7 by ! use ( su* *emicals t no hydrog5 is produc$4 #bdf4 ,local ,action4--,x is notic$ t :5 a /rip ( z9c is plac$ 9 dilute acid t bubbles appe> ^u ! surface ( ! z9c4 ,! appe>ance ( ^! bubbles indicates t "s ( ! hydrog5 ions c>ry+ positive electricity h mov$ to ! z9c plate4 ,c>eful exam9ation ( ! plate aft] x has be5 9 acid %[s num]\s black spots ^u x4 ,^! are bits ( c>bon4 ,!y are always f\nd 9 ord9>y z9c4 ,small electric curr5ts are set up :i* run f molecules ( pure z9c into ! liquid & back to ! c>bon p>ticles1 ?us =m+ small clos$ circuits4 7,see ,fig4 #bba47 ,! =mation ( ^! circuits f & to ! z9c is call$ local action4 ,?is action is a defect 9 voltaic cells s9ce a "p ( ! curr5t is ?us kept f pass+ ?r\gh ! ma9 outside circuit1 & ! z9c may be consum$ ev5 :5 no outside curr5t is fl[+4 ,illu/ration3 ,,fig4 #bba4--,local action4 #bdg4 ,amalgamation4--,local action is prev5t$ by coat+ ! z9c ) m]cury4 ,?is process is call$ amalgamation4 ,! m]cury cov]s ! entire surface ( ! plate 9 ! acid4 ,its action is to dissolve pure z9c & br+ x to ! out] surface :]e x is act$ ^u by ! acid4 ,! c>bon p>ticles are kept cov]$ s t no local curr5ts c be =m$ z long z ! bits ( c>bon are bel[ ! surface4 ,amalgamation !re=e prev5ts local action4 ,important ,topics ,! ,simple ,voltaic ,cell #a4 ,two plates3 z9c1 copp]2 electrolyte1 dilute sulphuric acid4 #b4 ,ions3 hydrog51 positive3 sulphion1 negative4 #c4 ,curr5t1 :]e & h[ produc$1 direction1 illu/ration4 #d4 ,pol>ization3 cure1 local action1 cure4 ,ex]cises #a4 ,write 9 y\r own words an acc\nt ( ! production ( an electric curr5t by ! simple voltaic cell4 ,use sket*es4 #b4 ,:i* plate has ! high] pot5tial8 ,h[ is x produc$8 #c4 ,w\ld y expect to get an ,e4,m4,f4 by =m+ a cell ( two copp] plates8 ,:y8 7#c7 ,,practical ,,voltaic ,,cells #bdh4 ,advantages ( ,voltaic ,cells4--,_m =ms ( voltaic cells h be5 devis$4 ,sev]al ( ! m common ( ^! w be describ$ & _! electro-*emical action expla9$4 ,at ! pres5t "t voltaic cells are employ$ only :]e small curr5ts are ne$$1 su* z = electric bells & induction coils4 ,:]e m ?an a small am\nt ( curr5t is requir$1 ! dynamo & ! /orage batt]y h g5]ally tak5 _! place z s\rces ( electric curr5t4 ,! advantages ( voltaic cells z electric g5]ators are3 7a7 !y are inexp5sive1 7b7 !y are easily tak5 f place to place1 7c7 !y may be ready = in/ant use4 ,! mo/ desirable voltaic cell w\ld be "o hav+ ! foll[+ qualities3 7a7 ,high electromotive =ce1 7b7 no pol>ization or local action1 7c7 v l[ int]nal resi/ance1 7d7 small exp5se1 bo? z to fir/ co/ & upkeep4 ,illu/ration3 ,,fig4 #bbb4--,! ,leclan* cell1 wet type4 #bdi4 ,! ,leclan* cell is ! "o commonly us$ = r++ door bells4 ,x has two plates3 "o ( z9c & ! o!r ( c>bon4 ,^! are plac$ 9 a solution ( sal ammoniac 7,fig4 #bbb74 ,take up ! desirable qualities m5tion$ at ! end ( ! prec$+ p>agraph4 7a7 ,x may be %[n t ?is cell has a good ,e4,m4,f4 ab\t #a4e volts4 7b7 ,x pol>izes easily yet x recov]s well :5 left ^u op5 circuit4 ,usually a sub/ance call$ manganese dioxide is mix$ ) ! c>bon4 ,?is acts z a depol>iz]1 t is1 x comb9es ) ! hydrog5 to =m wat]4 7c7 ,its resi/ance v>ies & is (t5 consid]able4 7d7 ,! exp5se = upkeep is small1 s9ce a #e-;c5t rod ( z9c1 & a #e-;c5t *>ge ( sal ammoniac w keep ! cell 9 action on a bell circuit f six mon?s to a ye> or m4 ,x is well suit$ = use on op5 circuits t is1 :]e ! circuit is op5 ! great] "p ( ! "t & is clos$ only occasionally2 z 9 r++ door bells1 op]at+ telephones1 & o!r devices ^: circuits are usually op54 #bej4 ,! ,dry ,cell4--,_m =ms ( ,leclan* cells are made4 ,"o ( ^! is call$ ! dry cell 7,see ,fig4 #bbc47 ,9 ?is cell ! z9c plate is made into a j> or c & conta9s ! o!r mat]ials4 ,at ! c5t] ( ! cell is a rod ( c>bon & manganese dioxide4 ,! space betwe5 ! c>bon & z9c is fill$ ) a por\s mat]ial su* z sawdu/ or pla/] ( ,p>is4 ,a /rong solution ( sal ammoniac fills ! por\s mat]ial4 ,! top ( ! cell is seal$ ) pit* or wax to prev5t evaporation4 ,! great advantage ( ?is cell is t x may be us$ or c>ri$ 9 any position )\t dang] ( spill+ its cont5ts4 ,dry cells are (t5 us$ to op]ate ! sp>k coils ( gas & gasol9e eng9es4 ,! ,leclan* cell describ$ 9 ,art4 #bdi is commonly kn[n z ! wet cell4 ,illu/ration3 ,,fig4 #bbc4--,! ,leclan* cell1 dry type4 ,illu/ration3 ,,fig4 #bbd4--,! ,daniell cell4 #bea4 ,! ,daniell ,cell4--,?is cell is (t5 us$ 9 laboratories1 & on clos$ circuits su* z ^? connect$ ) fire & burgl> al>ms & telegraph l9es4 ,x has two plates ( z9c & copp] plac$ 9 two diff]5t liquids :i* are kept sep>at$ by a por\s clay cup 7,fig4 #bbd74 ,! z9c rod is kept 9 a solution ( z9c sulphate conta9$ 9 ! por\s cup4 ,! copp] plate is 9 a solution ( copp] sulphate fill+ ! re/ ( ! glass j>4 ,unlike ! ,leclan* cell1 ?is "o mu/ be kept ^u a clos$ circuit to d its be/ "w1 z ! two liquids mix :5 ! circuit is op54 ,tak+ its qualities 9 ord]1 7a7 its ,e4,m4,f4 is ab\t "o volt1 7b7 x has no pol>ization s9ce copp] in/ead ( hydrog5 is deposit$ ^u ! copp] plate4 ,!re=e a uni=m ,e4,m4,f4 may be obta9$ f x1 mak+ x especially useful 9 laboratory exp]im5ts & te/s4 7c7 ,its resi/ance is consid]able & 7d7 x is m exp5sive to op]ate ?an ! ,leclan*4 ,x is sometimes us$ ^u clos$ circuits outside ( laboratories z 9 burgl> & fire al>ms1 al?\gh 9 rec5t ye>s1 ! /orage batt]y is tak+ its place = ^! purposes4 #beb4 ,! ,gravity ,cell4--,fig4 #bbe is l ! ,daniell cell 9 mo/ respects1 except t 9 ?is cell1 ! z9c plate is held at ! top ( ! j> 9 a solution ( z9c sulphate :ile ! copp] plate is at ! bottom1 surr\nd$ by a solution ( copp] sulphate4 ,! solutions mix b sl[ly z ! copp] sulphate solution is d5s] & rema9s at ! bottom4 ,?is cell l ! ,daniell mu/ also be kept ^u clos$ circuit4 ,on acc\nt ( its simplicity & economy x is (t5 us$ to op]ate telegraph in/rum5ts4 ,its qualities are simil> to ^? ( ! ,daniell cell4 ,illu/ration3 ,,fig4 #bbe4--,! gravity cell4 #bec4 ,symbol = ,voltaic ,cells4--,9 electrical diagrams1 ! symbol employ$ to repres5t a voltaic cell is a %ort ?ick l9e ne> to & p>allel to a long] ?9 "o4 ,z 9 ,fig4 #bbf4 ,if sev]al cells are to be repres5t$ ! conv5tional symbol ( ! comb9ation is repres5t$ z 9 ,fig4 #bbg4 ,a s+le cell & a gr\p ( cells are ea* frequ5tly call$ a batt]y4 ,illu/ration3 ,,fig4 #bbf4--;,diagram ( a s+le cell4 ,illu/ration3 ,,fig4 #bbg4--;,diagram ( a gr\p ( cells4 #bed4 ,effects ( ,electric ,curr5ts4--,hav+ /udi$ "s ( ! devices = produc+ an electric curr5t1 let u n[ consid] "s ( ! effects caus$ by x4 ,^! effects w be /udi$ "u ?ree heads3 7a7 ,magnetic1 7b7 ,*emical1 & 7c7 ,heat effects4 ,devices or articles %[+ ^! effects kn[n to mo/ high s*ool /ud5ts are respectively3 7a7 ! electromagnet 7b7 electro-plat$ silv] w>e & 7c7 electric heat]s1 su* z electric flat irons1 electric toa/]s1 etc4 ,! magnetic effect ( an electric curr5t 0 fir/ detect$ by ,o]/$ at ! ,univ]sity ( ,cop5hag5 9 #ahai4 ,x may be obs]v$ by hold+ a wire c>ry+ a curr5t f a voltaic cell above & p>allel to ! ne$le ( a magnetoscope4 ,! ne$le is at once deflect$ 7,fig4 #bbh74 ,if ! curr5t is rev]s$ 9 direction ! magnetoscope ne$le is deflect$ 9 ! rev]se direction4 ,?is simple device is ! mo/ common means = detect+ an electric curr5t4 ,x !re=e con/itutes a galvanoscope4 7,see ,art4 #bci47 ,illu/ration3 ,,fig4 #bbh4--;,a galvanoscope4 ,important ,topics #a4 ,leclan* cells1 7a71 wet1 7b71 dry1 con/ruction1 advantages1 uses4 #b4 ,daniell & gravity cells1 con/ruction1 advantages1 uses4 #c4 ,?ree effects ( electric curr5ts1 illu/rations4 #d4 ,! galvanoscope1 uses4 ,ex]cises #a4 ,expla9 h[ ! direction ( curr5t 9 a wire c be det]m9$ by a compass4 #b4 ,w\ld y expect to obta9 a curr5t f a z9c & copp] cell conta9+ a solution ( common salt8 ,p]=m ! exp]im5t4 #c4 ,:at conditions 9 a voltaic cell w give a /eady electromotive =ce4 #d4 ,:at conditions 9 a voltaic cell w give a /rong electromotive =ce4 #e4 ,"n ?ree diff]5t electric circuits t y "k exi/4 ,:i* are op5 & :i* are clos$ circuits8 #f4 ,are voltaic cells us$ 9 y\r home8 ,if s1 = :at purpose are !y us$8 ,on op5 or clos$ circuits8 ,h y se5 !m8 :at k9d are !y8 ,,*apt] ,,xii ,,! ,,magnetic ,,effect ,,( ,,electric ,,curr5ts4 ,,electrical ,,measurem5ts 7#a7 ,,! ,,magnetic ,,effect ,,( ,,electric ,,curr5ts #bee4 ,! ,magnetic ,effect4--,( all ! effects ( electric curr5ts1 x is g5]ally conc$$ t ! magnetic effect is ! "o ( greate/ practical importance1 & x is also ! "o mo/ ext5sively us$4 ,an exp]im5t illu/rat+ ?is effect has be5 describ$ 9 ,art4 #bci4 ,?is exp]im5t %[s t an electric curr5t1 if p>allel to a magnetic ne$le1 & ne> x w deflect ! nor?-seek+ pole ( ! ne$le to ! "r or left dep5d+ ^u ! direction ( ! curr5t fl[4 ,?is deflection ( ! magnetic ne$le is due to ! fact t surr\nd+ e electric curr5t are magnetic l9es ( =ce4 ,x is ?is magnetic field ( ! curr5t t causes ! ne$le to turn4 ,! position tak5 by ! ne$le is ! resultant ( ! =ces ( two magnetic fields2 "o1 ! e>?'s field1 ! o!r1 t ( ! curr5t4 #bef4 ,"r-h& ,rule = a ,conductor4--,to %[ ! pres5ce ( ! magnetic field ab\t a curr5t1 pass a ?ick copp] wire v]tically ?r\gh a %eet ( pap]1 & connect ! ends ( ! wire to a s\rce ( curr5t4 ,:ile ! curr5t 7?is %\ld be z mu* z #aj amp]es if possible7 is fl[+1 spr9kle iron fil+s ^u ! pap] & tap g5tly4 ,! fil+s w arrange !mselves 9 circles ab\t ! wire %[+ ! magnetic field4 7,see ,fig4 #bbi47 ,! ne$le ( a magnetoscope t5ds to place itself p>allel to ! l9es ( =ce ( ?is field & f ?is action or t5d5cy ! direction ( ! magnetic l9es ab\t a curr5t may be det]m9$4 ,! foll[+ rule is helpful & %\ld be memoriz$3 ,grasp ! conductor ) ! "r h& ) ! out/ret*$ ?umb 9 ! direction t ! curr5t is fl[+4 ,! f+]s w !n encircle ! wire 9 ! direction ( ! l9es ( =ce4 ,?is rule may be rev]s$1 =1 if ! f+]s ( ! "r h& grasp ! wire s z to po9t ) ! magnetic field1 !n ! curr5t fl[s 9 ! direction 9 :i* ! ?umb po9ts4 7,see ,fig4 #bcj47 ,illu/ration3 ,,fig4 #bbi4--,magnetic field ab\t a wire c>ry+ an electric curr5t4 ,illu/ration3 ,,fig4 #bcj4--,"r-h& rule = ! magnetic field ( a curr5t4 #beg4 ,magnetic ,field ( a ,helix4--,if a wire be w\nd ab\t a cyl9d] to =m a cyl9drical coil ) p>allel turns1 x =ms a helix or sol5oid4 ,! %ape ( ! magnetic field ab\t a curr5t dep5ds ^u ! =m ( ! conductor4 ,if ! latt] is 9 ! =m ( a helix its magnetic field resembles t ( a /raight b> magnet4 7,see ,fig4 #bca74 ,9 fact ! helix has ! prop]ties ( a magnet ) nor?- & s\?-seek+ poles :ile a curr5t is fl[+ ?r\gh x4 ,if su* a coil is susp5d$ s z to turn freely1 x t5ds to turn until ! field )9 x is p>allel to ! e>?'s magnetic field4 ,su* a susp5d$ helix may !re=e be us$ z a compass4 ,9 ord] to /r5g!n ! magnetic field ( a helix or sol5oid1 ! space )9 its turns is fill$ ) iron1 (t5 9 ! =m ( small s(t-iron wires4 ,?is bundle ( iron wire is call$ ! core ( ! helix4 ,! core becomes /rongly magnetiz$ by ! field ( ! helix :ile ! curr5t is fl[+ & quickly loses its magnetic =ce :5 ! curr5t is /opp$4 ,! direction ( ! curr5t 9 a helix 7,fig4 #bcb7 or ! pol>ity ( its core may be det]m9$ by ano!r "r-h& rule4 ,if ! helix is grasp$ ) ! "r h& s t ! f+]s po9t 9 ! direction 9 :i* ! curr5t is fl[+1 ! ext5d$ ?umb w po9t 9 ! direction ( ! nor? pole ( ! helix4 ,on ! o!r h&1 if ! poles ( ! helix are kn[n1 !n1 :5 ! helix is grasp$ ) ! "r h& s t ! ?umb po9ts to ! nor?-seek+ pole1 ! curr5t is fl[+ 9 ! wires 9 ! direction t ! f+]s po9t4 ,illu/ration3 ,,fig4 #bca4--,! magnetic field ( a helix4 ,illu/ration3 ,,fig4 #bcb4--,"r-h& rule = a helix4 #beh4 ,! ,electromagnet4--,^! "r-h& rules are appli$ 9 _m diff]5t devices4 ,among ^!1 p]haps ! mo/ important is ! electromagnet1 :i* is us$ 9 ! electric bell1 ! telegraph1 ! telephone1 ! dynamo1 ! motor1 & _m o!r electric contrivances4 ,! electromagnet is def9$ z a mass ( iron ar\nd :i* is plac$ a helix = conduct+ an electric curr5t4 ,on acc\nt ( its l>ge p]meability1 ! iron core ( ! helix adds greatly to ! effectiv5ess ( ! electromagnet1 s9ce ! magnetism ( ! iron is add$ to t ( ! curr5t 9 ! helix4 ,! magnetism rema9+ 9 ! iron aft] ! curr5t /ops is call$ ! residual magnetism4 ,! residual magnetism is small :5 ! core is made ( small wires or ?9 plates1 b is l>g] :5 ! iron core is solid4 ,l artificial /eel magnets1 electromagnets are usually ( two =ms1 b> & horse%oe4 7,see ,figs4 #bcc & #bcd47 ,= mo/ purposes ! horse%oe =m is ! m effective s9ce x p]mits a complete iron circuit = ! magnetic l9es ( =ce4 7,see ,fig4 #bce47 ,?is is ! =m us$ 9 ! electric bell1 9 ! telegraph s\nd]1 & 9 lift+ magnets4 7,see ,fig4 #bcf47 ,illu/ration3 ,,fig4 #bcc4--;,a b> electromagnet4 ,illu/ration3 ,,fig4 #bcd4--;,a horse%oe electromagnet4 ,illu/ration3 ,,fig4 #bce4--;,a horse%oe electromagnet may h a complete iron circuit = its l9es ( =ce4 ,illu/ration3 ,,fig4 #bcf4--;,a lift+ magnet4 #bei4 ,effective ,electromagnets4--,! magnetic effect ( a curr5t 9 a helix is small1 h5ce ! =ce usually is increas$ by ins]t+ a core ( iron4 ,:5 at fir/ man tri$ to signal ) electromagnets at a di/ance x 0 f\nd t ! curr5t w\ld n "w ! electromagnet4 ,an ,am]ican by ! "n ( ,joseph ,h5ry discov]$ ! rem$y = ?is condition4 ,he f\nd t if ! copp] wire 0 insulat$ by wrapp+ silk ?read ab\t x1 & !n _m lay]s ( ! silk insulat$ wire 7 w\nd ^u a spool ) an iron core1 t ! magnet w\ld "w at a great di/ance f ! s\rce ( curr5t4 ,if ! curr5t is increas$1 ! magnet is /rong] ?an at fir/4 ,?us an electromagnet may be made /rong] by 7a7 increas+ ! numb] ( turns ( wire 9 its coils & by 7b7 s5d+ a /rong] curr5t ?r\gh x4 ,illu/ration3 ,,fig4 #bcg4--;,a simple telegraph circuit4 #bfj4 ,! ,telegraph4--,! inv5tion ( an effective electromagnet by ,h5ry made possible ! electric telegraph4 ,9 its simple/ =m x consi/s ( a batt]y1 ,c1 a key1 ,k1 & a s\nd]1 ,s1 ) connect+ wires4 7,see ,fig4 #bcg47 ,! s\nd] 7,fig4 #bch7 conta9s a horse%oe electromagnet & a b> ( s(t iron across its poles call$ an armature1 ,a1 atta*$ to a lev] ,l4 ,:5 ! key is clos$1 ! electromagnet draws d[n ! armature & lev] until ! latt] hits a /op ,o1 mak+ a click4 ,:5 ! key is rais$1 ! magnet releases ! armature :i* is rais$ by ! action ( a spr+ at ,s until ! lev] hits a /op at ,t mak+ ano!r click4 ,clos+ & op5+ ! circuit at ,k w />t & /op ! curr5t :i* op]ates ,s :i* may be #ajj miles or m f ,k4 ,"o voltaic cell w "w a s\nd] 9 ! same room4 ,b if _m miles ( wire are 9 ! circuit1 ! ,e4,m4,f4 ( a s+le cell w n =ce suffici5t curr5t ?r\gh ! long wire to op]ate ! s\nd]4 ,illu/ration3 ,,fig4 #bch4--;,a telegraph s\nd]4 ,illu/ration3 ,,fig4 #bci4--;,a telegraph relay4 ,illu/ration3 ,,fig4 #bdj4--;,h[ ! relay is us$4 ,illu/ration3 ,samuel ,f4 ,b4 ,morse 7#agia-ahgb74 ,inv5tor ( ! electromagnetic record+ telegraph & ( ! dot & da% alphabet4 ,,samuel ,f4 ,b4 ,,morse ,f ,appleton's ,cyclop$ia ( ,am]ican ,biography1 ,copyright #ahhh by ,d4 ,appleton ,co4 ,illu/ration3 ,?omas ,a4 ,edison1 ,orange1 ,new ,j]sey4 ,inv5t$ ! inc&esc5t lamp2 phonograph2 mov+ picture2 mo/ not$ inv5tor ( electrical appliances ( ! pres5t day4 ,,?omas ,a4 ,,edison ,copyright1 ,photographis*e ,gessells*aft1 & ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,a batt]y ( sev]al cells is !n requir$4 ,ev5 a l>ge batt]y is insuffici5t to op]ate a long l9e conta9+ _m s\nd]s 9 circuit4 ,rec\rse is !re=e usually made to a m s5sitive device call$ a relay4 7,see ,fig4 #bci47 ,9 ! relay a v small curr5t w magnetize its electromagnet en\gh to draw t[>d x ! delicately hung armature !reby clos+ a second circuit :i* conta9s a s\nd] & a batt]y4 7,see ,fig4 #bdj47 :5 ! curr5t 9 ! ma9 circuit is /opp$1 ! armature ( ! relay is drawn back by a light spr+4 ,?is op5s ! local circuit4 ,?us ! local circuit is clos$ & op5$ by ! relay j 9 "t ) ! />t+ & /opp+ ( ! curr5t 9 ! ma9 l9e4 ,x is ?us possible = a small curr5t 9 ! ma9 l9e by ! use ( a relay1 to close & op5 a second local circuit conta9+ a local batt]y & s\nd]4 ,mod]n telegraph l9es are op]at$ 9 ?is mann]4 ,illu/ration3 ,,fig4 #bda4--;,an electric bell & its circuit4 #bfa4 ,! electric bell 7see ,fig4 #bda71 consi/s ( an electromagnet1 ,m1 a s(t iron armature1 ,a1 atta*$ to ! tapp]1 ,t1 & a po/1 ,r4 ,:5 no curr5t is fl[+ a spr+ at ,s holds ! armature aga9/ ! po/ ,r4 ,:5 curr5t fl[s ?r\gh ! helix1 its core becomes magnetiz$ & attracts ! armature1 draw+ x away f ! po/1 ,r1 & caus+ ! tapp] to hit ! bell4 ,draw+ ,a away f ! po/1 h[ev]1 breaks ! circuit at ,r & ! curr5t /ops4 ,! magnetism 9 ! core disappe>s releas+ ! armature1 :i* is !n pull$ back by ! spr+ ,s aga9/ ! po/ ,r4 ,?is completes ! circuit & ! process repeats itself sev]al times a second z long z ! curr5t fl[s4 ,illu/ration3 ,,fig4 #bdb4--,magnetiz+ by ! dis*>ge ( a ,leyd5 j>4 #bfb4 ,/atic & ,curr5t ,electricity ,comp>$4--,! lik5ess betwe5 a dis*>ge ( /atic electricity & an electric curr5t may be %[n by w9d+ a coil ( insulat$ wire ab\t a glass tube :i* conta9s a /eel ne$le4 ,if a ,leyd5 j> 7see ,fig4 #bdb7 is dis*>g$ ?r\gh ! coil ! /eel ne$le is usually f\nd to be magnetiz$1 %[+ t ! dis*>ge ( ! /atic electricity has a magnetic effect simil> to t ( an electric curr5t4 ,sometimes a giv5 end ( ! ne$le has a nor? pole & at o!r times a s\? pole4 ,?is is believ$ to indicate t ! *>ge ( ! ,leyd5 j> is oscillatory1 & t 9 diff]5t dis*>ges sometimes a surge 9 "o direction & at o!r times a surge 9 ! rev]se direction has be5 mo/ effective 9 magnetiz+ ! ne$le4 ,comp>e ?is action ) t describ$ 9 ,art4 #bcc4 ,important ,topics #a4 ,"r-h& rules1 = conductor1 = helix4 #b4 ,! electromagnet1 two =ms1 :]e us$8 #c4 ,lik5ess betwe5 /atic & curr5t electricity4 #d4 ,! electric bell1 p>ts1 action4 #e4 ,! telegraph1 key1 s\nd]1 relay4 ,ex]cises #a4 ,:at is ! diff]5ce betwe5 an electric *>ge & a curr5t8 #b4 ,h[ c a magnetic effect be produc$ f an electric *>ge8 #c4 ,:at is a magnetic field8 ,give two evid5ces ( a magnetic field ab\t a curr5t 9 a wire8 #d4 ,a curr5t is fl[+ nor? 9 trolley wire1 :at is ! direction ( ! magnetic field "u ! wire8 ,expla94 #e4 ,:at w\ld be ! result if a h>d /eel core 7 plac$ 9 ! electromagnet8 ,expla94 #f4 ,if ! nor?-seek+ pole ( a helix is fac+ y1 does ! curr5t 9 ! coils be=e y move 9 a clockwise or 9 a c\nt]-clockwise direction8 ,expla94 #g4 ,a helix is plac$ horizontally ) its nor?-seek+ pole t[>d ! nor?4 ,does ! curr5t 9 ! wire at ! top ( ! helix move ea/ or we/8 ,expla94 #h4 ,/ate at lea/ six conditions any "o ( :i* w put an electric bell circuit out ( commission4 #i4 ,if "o desires to ins]t a batt]y into a telegraph circuit already 9 op]ation1 h[ w he det]m9e ! direction ( ! curr5t 9 ! wire8 #aj4 ,if a boy :o _h magnetiz$ 8 knife blade 9 a physics laboratory1 po9t$ end s\?-seek+1 %\ld lose 8 way 9 ! woods on a cl\dy day1 h[ c\ld he det]m9e 8 way out8 #aa4 ,at a c]ta9 po9t ! e>?'s field acts nor?1 t ( an electric curr5t1 ea/4 ,! magnetoscope ne$le po9ts exactly nor!a/ :5 plac$ at t po9t4 ,h[ d ! two magnetic fields comp>e8 7#b7 ,,electrical ,,measurem5ts #bfc4 ,galvanomet]s4--,9 us+ electric curr5ts x is (t5 necess>y or desirable to be able to "k n only t a giv5 curr5t is weak or /rong1 b precisely :at its /r5g? is4 ,we c det]m9e ! relative /r5g?s ( two curr5ts by ! use ( a galvanomet]4 ,illu/ration3 ,,fig4 #bdc4--,! magnet is at ! c5t] ( ! coil4 ,illu/ration3 ,,fig4 #bdd4--;,a mov+-magnet 7tang5t7 galvanomet]4 ,! old] or mov+-magnet type ( galvanomet] is simil> to ! galvanoscope m5tion$ 9 ,art4 #bci4 ,x consi/s ( a magnetic ne$le m\nt$ at ! c5t] ( a coil ( wire4 ,! coil is plac$ fac+ ea/ & we/1 s t ! ne$le w be held by ! e>?'s magnetic field p>allel to ! plane ( ! coil4 ,:5 a curr5t is s5t ?r\gh ! coil a magnetic field is produc$ )9 x4 ,?is deflects ! ne$le1 its nor? end turn+ ea/ or we/ dep5d+ ^u ! direction ( ! curr5t4 7,see ,fig4 #bdc47 ,! coils ( a mov+-magnet or tang5t galvanomet] 7see ,fig4 #bdd7 are l>ge & firmly fa/5$ to ! base1 :ile ! magnet is small4 ,! mov+-coil type ( galvanomet] 7see ,fig4 #bde7 consi/s ( a l>ge magnet fa/5$ to ! frame ( ! device4 ,! magnet usually has a horse%oe =m to produce z /rong a field z possible4 ,! coil is w\nd on a light rectangul> frame & is susp5d$ betwe5 ! two poles ( ! magnet4 ,to conc5trate ! magnetic field1 a cyl9d] ( s(t iron is usually plac$ )9 ! coil4 ,fig4 #bdf repres5ts a common =m ( mov+-coil galvanomet]4 ,illu/ration3 ,,fig4 #bde4--,to illu/rate ! pr9ciple ( ! mov+-coil galvanomet]4 ,illu/ration3 ,,fig4 #bdf4--;,a mov+-coil 7,d',arsonval7 galvanomet]4 #bfd4 ,measurem5t ( ,electric ,curr5ts4--,a galvanomet] enables "o to comp>e electric curr5ts4 ,to measure electric curr5ts x is necess>y to employ a unit ( electrical quantity1 j z 9 measur+ ! quantity ( wat] deliv]$ by a pipe1 a unit ( liquid measure is employ$2 ?us1 e4g41 ! curr5t deliv]$ by a giv5 pipe may be #b gallons ( wat] p] second1 s 9 measur+ ! fl[ ( an electric curr5t "o may speak ( two c\lombs p] second4 ,! c\lomb is ! unit quantity ( electricity j z ! unit ( quantity ( wat] is ! gallon4 ,= mo/ practical purposes1 h[ev]1 we are m int]e/$ 9 ! rate or int5sity ( fl[ ( curr5t ?an 9 ! actual quantity deliv]$4 ,! unit ( rate ( fl[ or curr5t is call$ ! amp]e4 ,9 det]m9+ ! exact quantity ( an electric curr5t1 physici/s make use ( a device call$ a c\lomb met]4 7,see ,fig4 #bdg47 ,?is conta9s a solution ( silv] nitrate 9 :i* are plac$ two silv] plates4 ,! curr5t to be measur$ is s5t ?r\gh ! solution1 9 at "o plate & out at ! o!r4 ,! plate :]e ! curr5t goes 91 ! anode1 ,a 7,fig4 #bdg71 loses 9 weight s9ce "s ( ! silv] is dissolv$4 ,! plate :]e ! curr5t goes out1 ! ca?ode1 ,c1 increases 9 weight s9ce "s ( ! silv] is deposit$4 ,by an int]national agreem5t1 ! int5sity ( ! curr5t :i* deposits silv] at ! rate ( #j4jjaaah g4 p] second is #a amp]e4 ,?is is equal to #d4jbe g4 p] h\r4 ,illu/ration3 ,,fig4 #bdg4--;,a c\lomb met]1 ! anode ,a is sep>at$ f ! ca?ode ,c by a por\s cup4 ,! c\lomb is def9$ z ! quantity ( electricity deliv]$ by a curr5t ( "o amp]e dur+ "o second4 ,a #dj-watt-inc&esc5t lamp takes ab\t #j4d amp]e ( curr5t4 ,an arc lamp takes f #f to #ae amp]es4 ,a new dry cell may s5d #bj amp]es ?r\gh a te/+ met]4 ,a /reet c> may take f #ej to #ajj amp]es4 #bfe4 ,! ,ammet]4--,! me?od describ$ above is n us$ ord9>ily = measur+ curr5t /r5g?s on acc\nt ( its inconv5i5ce4 ,! usual device employ$ is an ammet]4 ,?is in/rum5t is a mov+-coil galvanomet]4 ,x conta9s1 w\nd on a light =m1 a coil ( f9e copp] wire4 ,! =m is m\nt$ on jewel be>+s betwe5 ! poles ( a /rong p]man5t horse%oe magnet4 7,see ,fig4 #bdh47 ,z 9 o!r mov+-coil galvanomet]s1 a s(t iron cyl9d] )9 ! =m conc5trates ! field ( ! magnet4 ,! =m & its coil is held 9 balance by two spiral spr+s :i* also conduct curr5t into & out ( ! coil4 ,only a small "p ( ! :ole curr5t measur$1 9 "s cases only #j4jjja passes ?r\gh ! coil1 ! l>g] "p ( ! curr5t pass+ ?r\gh a metal wire or /rip call$ a %unt,l 7see ,fig4 #bdh7 connect+ ! b9d+ po/s ( ! in/rum5t4 ,a fix$ fraction ( ! :ole curr5t fl[s ?r\gh ! coil4 ,its field cross+ ! field ( ! horse%oe magnet1 t5ds to turn until its turn+ =ce is balanc$ by ! spiral spr+s4 ,z ! coil turns x moves a po9t] atta*$ to x across a scale graduat$ to indicate ! numb] ( amp]es 9 ! :ole curr5t4 ,l ,a %unt is a conductor or coil connect$ 9 p>allel ) ano!r conductor or circuit4 ,x c>ries a "p ( ! curr5t4 ,illu/ration3 ,,fig4 #bdh4--;,diagram ( a comm]cial ammet]4 ,s is ! %unt4 ,x %\ld be not$ t :ile all ( ! curr5t measur$ pass$ ?r\gh ! ammet]1 b a small "p goes ?r\gh ! coil4 #bff4 ,resi/ance ( ,conductors4--,) an ammet] "o may /udy ! *ange produc$ 9 ! am\nt ( curr5t fl[+ 9 a wire :5 a *ange is made 9 ! wire conduct+ ! curr5t4 ,= example1 if "o measures ) an ammet] ! curr5t fl[+ f a dry cell ?r\gh a long & !n ?r\gh a %ort piece ( f9e copp] wire1 x w be se5 t less curr5t fl[s :5 ! long piece is us$4 ,t is1 ! long wire seems to h9d] or to resi/ ! pass+ ( ! curr5t m ?an ! %ort piece4 ,9 o!r words1 ! long wire is said to h m resi/ance4 ,! resi/ance ( a conduct+ body is affect$ by sev]al conditions4 7a7 ,x is directly proportional to ! l5g? ( ! conductor1 "o hundr$ feet ( wire hav+ twice ! resi/ance ( fifty feet4 7b7 ,x is inv]sely proportional to ! squ>e ( ! diamet]2 a wire #j4a in* 9 diamet] has f\r times ! resi/ance ( a wire #j4b in* 9 diamet]4 7c7 ,x diff]s ) diff]5t sub/ances1 iron hav+ ab\t six times z mu* z copp]4 7d7 ,x v>ies ) ! temp]ature1 metals hav+ great] resi/ance at a high] temp]ature4 ,s9ce silv] is ! be/ conductor kn[n1 ! resi/ances ( o!r sub/ances are comp>$ ) x z a /&>d4 ,! ratio ( ! resi/ance ( a wire ( any sub/ance z comp>$ to ! resi/ance ( a silv] wire ( exactly ! same diamet] & l5g? is call$ its relative resi/ance4 ,purifi$ sub/ances arrang$ 9 ord] ( increas+ resi/ance = ! same l5g? & sectional area 7,ayrton-,ma!r7 are giv5 on p4 #bid4 ,silv] anneal$ #a4jj ,copp] anneal$ f #a4jd to #a4ji ,alum9um anneal$ #a4fd ,nickel anneal$ #d4fi ,plat9um anneal$ #f4ji ,iron anneal$ #f4ef ,g]man ,silv] f #ab4hj to #bj4bj ,m]cury #fc4cj ,ni*rome #fg4ej ,c>bon f #bgjj4jj to #fgjj4jj #bfg4 ,! ohm1 ! unit ( resi/ance1 is def9$ by int]national agreem5t z foll[s3 ,an ohm is ! resi/ance ( a column ( pure m]cury1 #ajf4c cm4 long ) a cross-section ( a squ>e millimet] & at a temp]ature ( #j;,c4 ,x %\ld be not$ t ea* ( ! f\r conditions affect+ resi/ance is m5tion$ 9 ! def9ition1 viz41 l5g?1 cross-section1 mat]ial1 & temp]ature4 ,s9ce x is inconv5i5t to h&le m]cury1 /&>d resi/ance coils1 made ( an alloy ( high resi/ance are us$ 9 comp>+ & measur+ resi/ances4 ,a piece ( copp] wire ,no4 #bb 7diamet] #j4fdd mm47 #fj4 #e ft4 long has a resi/ance ( #a ohm4 ,see table p4 #bif4 ,! resi/ance ( "s telephone receiv]s is #ge ohms1 ( a telegraph s\nd]1 #d ohms1 ( a relay #bjj ohms4 #bfh4 ,resi/ance ( ,circuits4--,e "p ( an electrical circuit possesses resi/ance4 ,9 an electric-bell circuit1 = in/ance1 ! wires1 ! bell1 ! pu%-button1 & ! cell itself1 ea* (f]s a def9ite resi/ance to ! passage ( ! curr5t4 ,! resi/ance )9 ! cell is t]m$ int]nal resi/ance1 :ile ! resi/ance ( ! p>ts outside ( ! electric g5]ator is call$ ext]nal resi/ance4 #bfi4 ,electromotive ,=ce4--,9 ord] to set 9 motion any?+1 "s =ce mu/ be appli$4 ,?is is z true ( electricity z ( solids1 liquids1 or gases4 ,by analogy t :i* is ex]t$ by a batt]y or by a dynamo 9 caus+ curr5t to fl[ is call$ an electromotive =ce4 ,! unit ( electromotive =ce1 ! volt1 may be def9$ z ! electromotive =ce t w drive a curr5t ( #a amp]e ?r\gh ! resi/ance ( #a ohm4 ,! electromotive =ce ( a dry cell is ab\t #a4e volts1 ( a ,daniell cell #a4jh volts4 ,mo/ electric light circuits 9 build+s c>ry curr5t at #aaj or #bbj volts pressure4 ,curr5ts = /reet c>s h an electromotive =ce ( f #eej to #ffj volts4 ,illu/ration3 ,,fig4 #bdi4--;,diagram ( a comm]cial voltmet]4 #bgj4 ,! ,voltmet]4--,an in/rum5t = measur+ ! electromotive =ce ( electric curr5ts is call$ a voltmet] 7,fig4 #bdi74 ,x is usually a mov+-coil galvanomet]1 & is always ( high resi/ance4 ,x is l an ammet] 9 con/ruction & appe>ance4 ,9 fact1 a voltmet] is an ammet] :i* has _h its %unt remov$ or disconnect$4 ,9 place ( a %unt1 ! voltmet] uses a coil ( wire ( high resi/ance 7see ,r1 ,fig4 #bdi7 9 s]ies ) ! galvanomet] coil4 ,! high resi/ance ( ! voltmet] p]mits b a v small curr5t to fl[ ?r\gh x4 ,h5ce a voltmet] mu/ be plac$ across a circuit & n 9 x4 ,9 o!r words a voltmet] is connect$ 9 %unt1 :ile an ammet] is 9 s]ies ) ! circuit z is %[n 9 ,fig4 #bej4 ,,dim5sions ,,& ,,functions ,,( ,,copp] ,,wires ,column head+s3 ,b3 ,b4 ,s4 gauge numb] ,,mm3 ,millimet]s ,,sa3 ,sectional area 9 squ>e millimet]s ,,wl3 ,weight & l5g?1 ,d5sity #h4i1 feet p] p\nd ,r3 ,resi/ance at #bd;,c41 feet p] ohm ,c3 ,capacity 9 amp]es ---------------------------------------- ---------------------- ,diamet] ,b ------------- ,circul> ,,sa ,,wl ,r ,c ,mils ,,mm mils ---------------------------------------- --------------------- #jjjjdfj4jjjaa4fhdbaa1fjj4jjajg4bai #a4efai1ibi4gjjcab4j #jjjdji4fdjaj4djeafg1hje4jj #he4jbh #a4igae1hjd4ijjbfb4j #jjcfd4hjj #i4bffacc1jgi4dj #fg4dca #b4diab1ecd4bjjbbj4j #jcbd4iej #h4bedaje1eib4ej #ec4dgj #c4ac #i1ide4cjjahe4j #bbeg4fcj #f4edd #ff1cgc4jj #cc4fca #d4ii #f1bea4djjaca4j #dbjd4caj #e4ahi #da1gdb4jj #ba4aea #g4ic #c1ica4fjj #ib4c #fafb4jbj #d4aae #bf1bej4ej #ac4cja #ab4fa #b1dgb4djj #fe4b #habh4dij #c4bfd #af1eji4jj #h4cff #bj4je #a1eee4jjj #df4a #ajaja4hij #b4ehh #aj1cha4jj #e4bfj #ca4ch #igg4hjj #cb4e #ab #hj4hjh #b4jec #f1ebi4ij #c4cji #ej4fi #fae4jbj #bc4j #ad #fd4jhd #a4fbh #d1ajf4hj #b4jha #hj4ei #chf4hjj #af4b #af #ej4hbj #a4bia #b1ehb4ij #a4cji #abh4ad #bdc4bej #aa4e #ah #dj4cjc #a4jbd #a1fbd4cj #j4hbc #bjc4gf #aeb4iij #h4a #bj #ca4ifa #j4hab #a1jba4ej #j4eagf #cbd4jj #if4baj #e4g #bb #be4cdg #j4fdd #fdb4gj #j4cbee #eae4ae #fj4eaj #d4j #bd #bj4ajj #j4eaa #ejd4ja #j4bjdg #hai4ba #ch4jej #b4h #bf #ae4idj #j4dje #bed4ja #j4abhh #a1cjb4fa #bc4icj #b4j #bh #ab4fda #j4cba #aei4gi #j4jhjig #b1jga4bb #ae4jej #a4d #cj #aj4jbe #j4bee #ajj4ej #j4jejib #c1bic4ig #i4dff #a4j #cb #g4iej #j4bjb #fc4bj #j4jcbjc #e1bcf4ff #e4ieb #j4gj #cd #f4cjd #j4afj #ci4gd #j4jbjad #h1cbh4cj #c4gdc #j4ej #cf #e4jjj #j4abg #be4jj #j4jabfgac1bch4hc #b4cee #j4ce #ch #c4ife #j4aja #ae4gb #j4jjgigbj1hed4fe #a4dha #j4be #dj #c4add #j4jhj #i4hi #j4jjejacc1age4id #j4ica #j4ag ---------------------------------------- --------------------- ,important ,topics 7#a7 ,galvanomet]s3 7#a7 mov+ magnet1 fix$ coil2 7#b7 mov+ coil1 fix$ magnet1 ammet]1 voltmet]4 7#b7 ,unit ( quantity1 c\lomb4 7#c7 ,unit ( curr5t1 amp]e4 7#d7 ,unit ( resi/ance1 ohm4 7#e7 ,unit ( electromotive =ce1 volt4 ,ex]cises #a4 ,h[ w ! resi/ance ( #bj ft4 ( ,no4 #bb ,g]man silv] wire comp>e ) t ( #aj ft4 ( ,no4 #bb copp] wire8 ,expla94 #b4 ,:]e 9 a circuit is copp] wire desirable8 ,:]e %\ld ,g]man silv] wire be us$8 #c4 ,expla9 ! action ( ! ammet]4 ,:y does n ! ne$le or coil sw+ ! full di/ance ) a small curr5t8 #d4 ,:y is a telegraph s\nd] m apt to "w on a %ort l9e ?an ^u a long "o8 ,illu/ration3 ,,fig4 #bej4--,! ammet] is connect$ 9 s]ies & ! voltmet] 9 %unt4 #e4 ,f9d ! resi/ance ( #ae miles ( copp] telephone wire ,no4 #ab4 7,see table p4 #bif47 #f4 ,:at w be ! weight & resi/ance ( #a1jjj feet ( ,no4 #bj copp] wire8 #g4 ,a /orage batt]y s5ds #d amp]es ( curr5t ?r\gh a plat+ solution4 ,h[ mu* silv] w x deposit 9 #b h\rs8 #h4 7a7 ,comp>e ! diamet]s ( ,no4 #bb & ,no4 #af copp] wire4 7b7 ,comp>e ! l5g?s ( ! same wires giv+ #a ohm resi/ance4 7c7 ,:at relation exi/s betwe5 7a7 & 7b78 #i4 ,:y is an electric bell circuit usually op5 :ile a telegraph l9e circuit is usually clos$8 #aj4 ,a copp] wire & an iron wire ( ! same l5g? are f\nd to h ! same resi/ance4 ,:i* is ?ick]8 ,:y8 #aa4 ,:y are electric bells usually arrang$ 9 p>allel in/ead ( 9 s]ies8 #ab4 ,:at w\ld happ5 if a voltmet] 7 put 9 s]ies 9 a l9e8 7#c7 ,,ohm',s ,,law ,,& ,,electrical ,,circuits #bga4 ,conditions ,affect+ ,curr5t ,fl[4--,sometimes ov] a long circuit "o cell w n "w a telegraph s\nd]4 ,9 su* a case1 two1 ?ree1 or m cells are connect$ s t ! z9c ( "o is jo9$ to ! copp] plate ( ! o!r4 ,:5 connect$ 9 ?is way ! cells are said to be 9 s]ies 7,fig4 #bea74 ,9 ! figure ,a repres5ts a voltmet]4 ,x is f\nd t :5 cells are 9 s]ies ! ,e4,m4,f4 ( ! batt]y is ! sum ( ! electromotive =ces ( ! cells4 ,an ammet] 9 ! circuit %[s increas$ curr5t z ! cells are add$4 ,h5ce if ! resi/ance ( ! circuit rema9s un*ang$1 ! great] ! ,e4,m4,f4 ! great] is ! curr5t /r5g?4 ,9 ?is respect1 ! movem5t ( electricity 9 a circuit is simil> to ! fl[ ( wat] 9 a small pipe "u pressure1 z 9 ! latt] ! fl[ ( wat] increases z ! pressure becomes great]4 ,! curr5t 9 a circuit may also be increas$ by less5+ ! resi/ance1 s9ce ! curr5t ?r\gh a long wire is less ?an t ?r\gh a %ort "o1 j z ! fl[ ( wat] w be great] ?r\gh a %ort pipe ?an ?r\gh a long "o4 ,to increase ! curr5t fl[+ 9 an electric circuit1 "o may !re=e ei!r increase ! ,e4,m4,f4 or decrease ! resi/ance4 ,illu/ration3 ,,fig4 #bea4--;,diagram ( cells connect$ 9 s]ies4 #bgb4 ,ohm's ,law4--,! relation betwe5 ! electromotive =ce appli$ to a circuit1 its resi/ance1 & ! curr5t produc$ 0 discov]$ 9 #ahbg by ,george ,ohm4 ,ohm's law1 "o ( ! mo/ important laws ( electricity1 /ates t1 9 any circuit1 ! curr5t 9 amp]es equals ! electromotive =ce 9 volts divid$ by ! resi/ance 9 ohms4 ,?is pr9ciple is usually express$ ?us3 ,curr5t int5sity electromotive =ce_/resi/ance or ,amp]es volts_/ohms or ,i ,e_/,r ,illu/ration3 ,,fig4 #beb4--,! /reet c>s are connect$ 9 p>allel ) ea* o!r4 #bgc4 ,resi/ance ( ,conductors 9 ,s]ies4--,a /udy ( ! resi/ance ( conductors :5 alone & :5 gr\p$ 9 v>i\s ways is ( importance s9ce1 ! curr5t fl[ ?r\gh any circuit is dep5d5t ^u its resi/ance4 ,! two mo/ common me?ods ( comb9+ sev]al conductors 9 a circuit are 9 s]ies & 9 p>allel4 ,conductors are 9 s]ies :5 all ( ! curr5t passes ?r\gh ea* ( ! conductors 9 turn 7,fig4 #bah71 ?us ! cell1 pu%-button1 wires1 & electric bell 9 an electric-bell circuit are 9 s]ies4 ,conductors are 9 p>allel :5 !y are s connect$ t !y are side by side & a "p ( ! :ole curr5t goes ?r\gh ea*4 ,none ( ! curr5t t passes ?r\gh "o conductor c g ?r\gh ! conductors 9 p>allel ) x4 ,?us ! electric /reet c>s are 9 p>allel ) ea* o!r4 7,see ,fig4 #beb47 ,x is easily se5 t none ( ! curr5t pass+ ?r\gh "o c> c g ?r\gh any ( ! o!rs4 ,:5 ! conductors are 9 s]ies ! comb9$ resi/ance is ! sum ( ! sev]al resi/ances4 ,?us 9 an electric-bell circuit if ! batt]y has a resi/ance ( #a ohm1 ! bell ( #b ohms1 & ! wire #a ohm1 ! total resi/ance 9 ! circuit is #d ohms4 ,:5 conductors are 9 p>allel ! comb9$ resi/ance is always less ?an ! sep>ate resi/ances4 ,j z a cr[d ( p meets less resi/ance 9 leav+ a build+ ?r\gh sev]al exits1 s electricity f9ds less resi/ance 9 mov+ f "o po9t to ano!r along sev]al p>allel l9es1 ?an along "o ( ! l9es4 #bgd4 ,resi/ance ( ,conductors 9 ,p>allel4--,if ?ree conductors ( equal resi/ance are 9 p>allel1 ! comb9$ resi/ance is j "o-?ird ! resi/ance ( ea* sep>ately 7,fig4 #bec74 ,! rule t /ates ! relation betwe5 ! comb9$ resi/ance ( conductors 9 p>allel & ! sep>ate resi/ances is z foll[s3,! comb9$ resi/ance ( conductors 9 p>allel is ! reciprocal ( ! sum ( ! reciprocals ( ! sev]al resi/ances4 ,= example1 f9d ! comb9$ resi/ance ( ?ree unequal resi/ances 9 p>allel2 ! fir/ be+ #d ohms1 ! second1 #f ohms1 & ?ird #c ohms4 ,! reciprocals ( ! ?ree resi/ances are #a_/d1 #a_/f1 & #a_/c4 ,_! sum equals #f_/bd #d_/bd #h_/bd #ah_/bd4 ,! reciprocal ( ?is is #bd_/ah :i* equals #a-a_/c ohms1 ! comb9$ resi/ance4 ,,fig4 #bec4--,! ?ree conductors are connect$ 9 p>allel4 ,?is rule may be und]/ood bett] if we consid] ! conductance ( ! conductors 9 p>allel4 ,s9ce ! conductance ( a two ohm wire is j "o-half t ( a "o-ohm wire1 we say t ! conductance ( a body is inv]sely z ! resi/ance1 or t x is ! reciprocal ( ! resi/ance4 ,! conductance ( ! #d-1 #f-1 & #c-ohm coils w !re=e be respectively #a_/d1 #a_/f1 & #a_/c1 & s9ce ! comb9$ conductance is ! sum ( ! sev]al conductances1 ! total conductance is #ah_/bd4 ,also s9ce ?is is ! reciprocal ( ! total resi/ance1 ! latt] is #bd_/ah or #a-a_/c ohms4 ,:5 two or m conductors are connect$ 9 p>allel ea* "o is said to be a %unt ( ! o!rs4 ,_m circuits are connect$ 9 %unt or 9 p>allel4 ,fig4 #bed repres5ts f\r lamps 9 p>allel4 ,inc&esc5t lamps 9 build+s are usually connect$ 9 p>allel1 :ile arc lamps are usually connect$ 9 s]ies4 ,fig4 #bee repres5ts f\r lamps 9 s]ies4 ,important ,topics #a4 ,conditions affect+ curr5t fl[1 7a7 ,e4,m4,f41 7b7 resi/ance4 #b4 ,ohm's law1 ?ree =ms = =mula4 #c4 ,resi/ance ( conductors3 7a7 9 s]ies1 7b7 9 p>allel2 h[ comput$1 illu/rations4 ,illu/ration3 ,,fig4 #bed4--,! f\r lamps are connect$ 9 p>allel4 ,illu/ration3 ,,fig4 #bee4--,! f\r lamps are connect$ 9 s]ies4 ,ex]cises #a4 ,:at curr5t fl[s ?r\gh a circuit if its ,e4,m4,f4 is #aaj volts & ! resi/ance is #bbj ohms8 #b4 ,a circuit conta9s f\r conductors 9 s]ies ) resi/ances ( #aj1 #ae1 #f1 & #i ohms respectively4 ,:at curr5t w fl[ ?r\gh ?is circuit at #aaj volts pressure8 ,:at w be ! resi/ance ( ^! f\r conductors 9 p>allel8 #c4 ,:at is ! comb9$ resi/ance ( #h conductors 9 p>allel if ea* is #bbj ohms8 ,:at curr5t w fl[ ?r\gh ^! #h conductors at #aaj volts pressure8 #d4 ,:at is ! resi/ance ( a circuit c>ry+ #bb amp]es1 if ! ,e4,m4,f4 is #bj volts8 #e4 ,:at ,e4,m4,f4 w s5d #h amp]es ( curr5t ?r\gh a circuit ( #ge ohms resi/ance8 #f4 ,h[ does ! voltmet] diff] f ! ammet]8 #g4 ,h[ c "o det]m9e ! resi/ance ( a conductor8 #h4 ,! resi/ance ( a hot inc&esc5t lamp is #ajj ohms4 ,! curr5t us$ is #a4a amp]es4 ,f9d ! ,e4,m4,f4 appli$4 #i4 ,:at is ! resi/ance ( ! wires 9 an electric heat] if ! curr5t us$ is #aj amp]es1 ! voltage be+ #aaj8 #aj4 ,! resi/ance ( #ajjj ft4 ( ,no4 #cf copp] wire is #dbd ohms4 ,h[ _m feet %\ld be us$ 9 w9d+ a #bjj ohms relay8 #aa4 ,! resi/ance ( ,no4 #jj trolley wire is #j4hj ohm p] #ajjj ft4 ,:at is ! resi/ance ( a l9e #a mile long8 #ab4 ,a wire has a resi/ance ( #bj ohms4 ,x is jo9$ 9 p>allel ) ano!r wire ( #f ohms1 f9d _! comb9$ resi/ance4 #ac4 ,! sep>ate resi/ances ( two inc&esc5t lamps are #bjj ohms & #gj ohms4 ,:at is _! comb9$ resi/ance :5 jo9$ 9 p>allel8 ,:5 jo9$ 9 s]ies8 7#d7 ,,me?ods ,,( ,,gr\p+ ,,cells ,,& ,,measur+ ,,resi/ance #bge4 ,int]nal ,resi/ance ( a ,voltaic ,cell4--,! curr5t produc$ by a voltaic cell is affect$ by ! resi/ance t ! curr5t meets 9 pass+ f "o plate to ano!r ?r\gh ! liquid ( ! cell4 ,?is is call$ ! int]nal resi/ance ( ! cell4 ,a ,daniell cell has sev]al 7#a-e7 ohms int]nal resi/ance4 ,! resi/ance ( dry cells v>ies f less ?an #j4a ( an ohm :5 new to sev]al ohms :5 old4 ,if cells are jo9$ toge!r _! comb9$ int]nal resi/ance dep5ds ^u ! me?od ( gr\p+ ! cells4 ,illu/ration3 ,,fig4 #bef4--,! f\r cans ex]t f\r times ! wat] pressure t "o c w ex]t4 #bgf4 ,cells ,gr\p$ 9 ,s]ies & 9 ,p>allel4--,:5 9 s]ies ! copp] or c>bon plate ( "o cell is jo9$ to ! z9c ( ano!r & s on4 7,see ,fig4 #bea47 ,! effect ( connect+1 say f\r cells1 9 s]ies may be illu/rat$ by tak+ f\r cans ( wat]1 plac$ "o above ano!r4 7,see ,fig4 #bef47 ,! comb9$ wat] pressure ( ! s]ies is ! sum ( ! sev]al pressures ( ! cans ( wat]1 :ile ! opposition (f]$ to ! movem5t ( a quantity ( wat] ?r\gh ! gr\p ( cans is ! sum ( ! sev]al resi/ances ( ! cans4 ,9 apply+ ?is illu/ration to ! voltaic cell1 we make use ( ,ohm's law4 ,let ,e repres5t ! e4m4f4 ( a s+le cell1 r ! int]nal resi/ance ( ! cell1 & ,r ! ext]nal resi/ance or ! resi/ance ( ! re/ ( ! circuit4 ,consid] a gr\p ( cells 9 s]ies4 ,if n repres5ts ! numb] ( cells 9 s]ies1 !n ,ohm's law becomes ,i n,e_/7nr ,r74 ,cells are gr\p$ 9 s]ies :5 l>ge ,e4,m4,f4 is requir$ to =ce a curr5t ?r\gh a l>ge ext]nal resi/ance su* z ?r\gh a long telegraph l9e4 ,cells are connect$ 9 p>allel :5 x is desir$ to s5d a l>ge curr5t ?r\gh a small ext]nal resi/ance4 ,to connect cells 9 p>allel all ! copp] plates are jo9$ & also all ! z9c plates4 7,see ,fig4 #beg47 ,to illu/rate ! effect ( ?is mode ( gr\p+ cells1 suppose sev]al cans ( wat] are plac$ side by side 7,fig4 #beh74 ,x is easily se5 t ! pressure ( ! gr\p is ! same z t ( a s+le cell1 :ile ! resi/ance to ! fl[ is less ?an t ( a s+le cell4 ,apply+ ?is reason+ to ! electric circuit we h by ,ohm's law ! =mula = ! curr5t fl[ ( a gr\p ( n cells arrang$ 9 p>allel ,i ,e_/77r_/n7 ,r74 ,illu/ration3 ,,fig4 #beg4--;,f\r cells connect$ 9 p>allel4 ,illu/ration3 ,,fig4 #beh4--,! wat] pressure ( ! gr\p 9 p>allel is ! same z t ( "o4 #bgg4 ,illu/rative ,problems4--,suppose t f\r cells are gr\p$ 9 p>allel1 ea* ) an ,e4,m4,f4 ( #a4e volts & an int]nal resi/ance ( #b ohms4 ,:at curr5t w fl[ 9 ! circuit if ! ext]nal resi/ance is #b4e ohms8 ,sub/itute 9 ! =mula = cells 9 p>allel ! values giv5 above1 & we h ,i #a4e_/7j4e #b4e7 #a4e_/c #j4e amp]e4 ,suppose aga9 t ^! f\r cells 7 gr\p$ 9 s]ies ) ! same ext]nal resi/ance1 sub/itut+ ! values 9 ! =mula = cells 9 s]ies we h ,i #d7a4e7_/7d #b #b4e7 #f_/aj4e #j4eg amp]e4 #bgh4 ,volt-ammet] ,me?od = ,f9d+ ,resi/ance4--,measurem5ts ( ! resi/ance ( conductors are (t5 made4 ,"o ( ^! me?ods dep5ds ^u an application ( ,ohm's law4 ,x is call$ ! volt-ammet] me?od s9ce x employs bo? a voltmet] & an ammet]4 ,if ! conductor ^: resi/ance is to be measur$ is made a "p ( an electric circuit1 be+ connect$ 9 s]ies ) ! ammet] & 9 %unt ) ! voltmet]1 ! resi/ance may easily be det]m9$1 s9ce ,r ,e_/,i4 7,see ,fig4 #bej47 ,if1 = example1 ! diff]5ce 9 ,e4,m4,f41 or z x is (t5 call$1 ! fall ( pot5tial betwe5 ! ends ( ! wire z read on ! voltmet] is #b volts1 & ! curr5t is #j4e amp]e1 !n ! resi/ance ( ! wire is #d ohms4 ,?is me?od may be readily appli$ to f9d ! resi/ance ( any wire t is a "p ( an electric circuit4 #bgi4 ,! ,:eat/one ,bridge4--,to f9d ! resi/ance ( a sep>ate wire or ( an electrical device ano!r me?od devis$ by an ,engli%man nam$ ,:eat/one is commonly employ$4 ,?is me?od requires t ?ree kn[n resi/ances1 a1 b1 c1 9 addition to ! unkn[n resi/ance x be tak54 ,^! f\r resi/ances are arrang$ 9 ! =m ( a p>allelogram4 7,see ,fig4 #bei47 ,a voltaic cell is jo9$ to ! p>allelogram at ! extremities ( "o diagonal :ile a mov+-coil galvanomet] is connect$ across ! extremities ( ! o!r diagonal4 ,! kn[n resi/ances are *ang$ until :5 on press+ ! keys at ,e & ,k no curr5t fl[s ?r\gh ! galvanomet]4 :5 ?is condition is rea*$1 ! f\r resi/ances =m a true proportion1 ?us a3 b c3 x4 ,s9ce ! values ( a1 b1 & c are kn[n1 x is readily comput$4 ,?us if a #aj1 b #ajj1 & c #a4h ohms1 !n x1 ! unkn[n resi/ance1 equals #ah ohms1 s9ce #aj3 #ajj #a4h3 #ah4 ,?is me?od devis$ by ,:eat/one may be employ$ to f9d ! resi/ance ( a great v>iety ( objects4 ,x is ! "o mo/ commonly employ$ by sci5ti/s & practical electricians4 ,illu/ration3 ,,fig4 #bei4--;,diagram ( a ,:eat/one bridge4 ,important ,topics #a4 ,! int]nal resi/ance ( voltaic cells4 #b4 ,ohm's law appli$ to gr\ps ( cells4 7a7 ,cells 9 s]ies1 7b7 cells 9 p>allel4 #c4 ,measurem5t ( resi/ance3 7a7 volt-ammet] me?od1 7b7 ,:eat/one bridge me?od4 ,ex]cises #a4 ,:at is ! resi/ance ( an electric bell circuit :]e ! ,e4,m4,f4 is #c volts & ! curr5t is #j4f amp]e8 #b4 ,a telegraph wire is brok5 some:]e1 ! ends ly+ ^u damp gr\nd4 ,if an ,e4,m4,f4 ( #cj volts is appli$ f ! gr\nd to ! wire & a curr5t ( #j4a ( an amp]e fl[s1 :at is ! resi/ance ( ! "p connect$ to ! ammet]4 7,! e>? :i* completes ! circuit f ! end ( ! wire has v small resi/ance47 ,:y8 #c4 ,h[ f> away is ! break 9 ! wire if ! latt] has a resi/ance ( #hj ohms to ! mile8 ,diagram4 #d4 ,:at curr5t w fl[ ?r\gh a bell circuit ( #h ohms resi/ance if x conta9s ?ree cells 9 s]ies ea* ) an ,e4,m4,f4 ( #a4e volts & an int]nal resi/ance ( #a_/c ohm8 #e4 ,if ! same ?ree cells are connect$ 9 p>allel on ! same circuit :at curr5t fl[s8 ,is ! curr5t 9 problem #d or #e ! l>g]8 ,:y8 #f4 ,if f\r cells ea* ) #a4e volts ,e4,m4,f4 & an int]nal resi/ance ( #j4d ohm are connect$ ) a circuit hav+ an ext]nal resi/ance ( #j4h ohm1 :at curr5t w ! p>allel connection give8 ,! s]ies connection8 ,:i* gives ! l>g] curr5t8 ,:y8 #g4 ,f\r ,daniell cells ea* hav+ #a volt ,e4,m4,f4 & #c ohms int]nal resi/ance are connect$ 9 s]ies ) #b telegraph s\nd]s ( #d ohms ea*4 ,! connect+ wires h #f ohms resi/ance4 ,f9d ! curr5t int5sity4 #h4 ,a batt]y ( #b cells arrang$ 9 s]ies is us$ to r+ a door bell4 ,! ,e4,m4,f4 ( ea* cell is #a4e volts1 int]nal resi/ance #j4c ohm1 & ! resi/ance ( ! bell is #d ohms4 ,:at is ! curr5t 9 amp]es8 #i4 ,9 ! above problem f9d ! curr5t if ! cells are connect$ 9 p>allel4 ,,*apt] ,,xiii ,,! ,,*emical ,,& ,,heat ,,effects ,,( ,,electric ,,curr5ts 7#a7 ,,! ,,*emical ,,effect ,,( ,,an ,,electric ,,curr5t #bhj4 ,electroplat+4--,if two c>bon rods 7electric light c>bons answ] v well7 are plac$ 9 a solution ( copp] sulphate 7,fig4 #bfj7 & !n connect$ by wires to ! b9d+ po/s ( an electric batt]y1 "o ( ! rods soon becomes cov]$ ) a coat+ ( metallic copp] :ile bubbles ( gas may be se5 ^u ! o!r c>bon4 ,if a solution ( lead acetate is us$ 9 ! same way a deposit ( metallic lead is secur$1 :ile a solution ( silv] nitrate gives silv]4 ,illu/ration3 ,,fig4 #bfj4--,two c>bons plac$ 9 a solution ( copp] sulphate4 ,illu/ration3 ,,fig4 #bfa4--;,an electroplat+ ba?4 ,?is process ( deposit+ metals ^u ! surface ( solids by an electric curr5t is call$ electroplat+4 ,ev]yone has se5 electroplat$ articles su* z silv] plat$ knives1 =ks1 & spoons1 & nickel-plat$ rods1 h&les1 etc4 ,copp] electrotype plates su* z are us$ 9 pr9t+ s*ool books are made by ?is process4 ,9 practical electroplat+ a solution ( ! metal to be deposit$ is plac$ 9 a tank2 across ! top ( ?is tank are plac$ copp] rods to act z conduct+ supports4 ,f "o ( ^! rods1 ! ca?ode1 objects to be plat$ are hung s z to be imm]s$ 9 ! liquid4 ,f o!r rods1 ! anodes1 are hung plates ( ! metal to be deposit$4 ,^! are dissolv$ z ! curr5t deposits a coat+ ^u ! articles1 ?us keep+ ! solution up to its prop] /r5g?4 7,see ,fig4 #bfa47 ,illu/ration3 ,,fig4 #bfb4--,! curr5t is c>ri$ ?r\gh ! solution by ions4 #bha4 ,electrolysis4--,a solution f :i* a deposit is made by an electric curr5t is call$ an electrolyte4 ,! plates or o!r objects by :i* ! curr5t ent]s or leaves ! electrolyte are call$ ! electrodes4 ,! electrode by :i* ! curr5t ent]s is call$ ! anode 7an 97 :ile ! electrode by :i* x leaves is ! ca?ode 7ca? away74 ,! process by :i* an electric curr5t decomposes a solution & deposits a sub/ance ^u an electrode is call$ electrolysis4 ,! curr5t always fl[s )9 ! cell f anode to ! ca?ode4 7,see ,fig4 #bfb47 ,! metal goes ) ! curr5t & is f\nd deposit$ ^u ! ca?ode4 #bhb4 ,!ory ( ,electrolysis4--,! action go+ on 9 an electrolytic cell has be5 c>efully /udi$4 ,! !ory ( electrolysis1 :i* is support$ by mu* exp]im5tal evid5ce1 supposes t _m ( ! molecules 9 a dilute solution ( a sub/ance split up into two p>ts call$ ions1 "o ion hav+ a positive1 ! o!r a negative *>ge4 ,9 a dilute solution ( sulphuric acid1 ! positive ion is ( hydrog51 :ile ! negative ion is ! 7,,s#d7 or sulphion4 ,^! ions be>+ electric *>ges are believ$ to be ! c>ri]s ( ! electric curr5t ?r\gh ! electrolyte4 ,! positive ions move ) ! curr5t f ! anode to ! ca?ode1 :ile ! negative ions app>5tly are repell$ by ! ca?ode & appe> ^u ! anode4 ,evid5ce ( ! accumulation ( ! two k9ds ( ions at ! two electrodes is furni%$ by ! electrolysis ( wat]1 describ$ bel[4 #bhc4 ,electrolysis ( ,wat]4--,two glass tubes 7,fig4 #bfc71 ,h & ,o1 are atta*$ at ! bottom to a horizontal glass tube4 ,to ! latt] is also connect$ an upright tube ,t4 ,at ! l[] ends ( ,h & ,o are ins]t$1 fus$ 9 ! glass1 plat9um wires1 ,a & ,c4 ,! tubes are fill$ ) a weak solution ( sulphuric acid4 ,! tops ( ,h & ,o are clos$ ) /opcocks1 ,t be+ op52 a curr5t ( electricity is s5t 9 at ,a & out at ,c4 ,a movem5t ( ! ions at once beg9s1 ! positive hydrog5 ions appe>+ at ,c4 ,^! accumulate z bubbles ( hydrog5 :i* rise to ! top ( ,h & displace ! liquid4 ,at ! same "t bubbles ( oxyg5 appe> at ,a4 ,^! rise 9 ,o & also displace ! liquid :i* rises 9 ,t4 ,aft] ! action has cont9u$ "s "t x may be notic$ t ! volume ( hydrog5 is j twice t ( ! oxyg54 ,?is 0 to h be5 expect$ s9ce ! =mula = wat] is ,h#b,o4 ,! nature ( ! gas 9 ,h or ,o may be te/$ by op5+ ! /opcock & all[+ ! gas to escape sl[ly4 ,! hydrog5 gas c be light$ by a flame :ile ! oxyg5 gas w cause a sp>k ^u a piece ( wood to gl[ brightly1 b does n burn itself4 ,illu/ration3 ,,fig4 #bfc4-;,electrolysis ( wat]2 oxyg5 collects 9 ,o1 hydrog5 9 ,h4 #bhd4 ,evid5ce t ions are necess>y to conduct a curr5t 9 a liquid is furni%$ by ! foll[+ exp]im5t4 ,a qu>t j> is c>efully clean$1 & half fill$ ) di/ill$ wat]4 ,two pieces ( z9c #e cm4 squ>e are sold]$ to pieces ( rubb]-insulat$ ,no4 #ad copp] wire4 ,! z9cs are plac$ 9 ! di/ill$ wat] 7,fig4 #bfd7 & ! wires are connect$ to a #aaj volt circuit ) a #af c&le-p[] inc&esc5t lamp 9 s]ies ) ! cell1 z 9 ! figure4 ,if ! z9cs h be5 c>efully cleans$ & ! wat] is pure1 no curr5t fl[s z is %[n by ! lamp rema9+ d>k4 ,if a m9ute quantity ( sulphuric acid or ( common salt is plac$ 9 ! wat] ! lamp at once beg9s to gl[4 ,ions are n[ pres5t 9 ! liquid & conduct ! curr5t4 ,t "s sub/ances 9 solution d n =m ions may be %[n by add+ to ano!r j> ( pure wat] "s glyc]9e & "s cane sug>1 sub/ances resembl+ ! acid & salt 9 ext]nal appe>ance b :i* d n ionize :5 dissolv$ z is %[n by ! lamp rema9+ d>k aft] add+ ! glyc]9e & sug>4 ,! acid & salt are ( m9]al orig9 :ile ! glyc]9e & sug> are vegetable products4 ,?is exp]im5t illu/rates ! pr9ciple t ! wat] w conduct only :5 x conta9s ions4 ,illu/ration3 ,,fig4 #bfd4--,! curr5t passes only :5 ions are pres5t 9 ! liquid4 #bhe4 ,laws ( ,electrolysis4--,^! 7 discov]$ by ,f>aday 9 #ahcc1 & may be /at$ z foll[s3 ,i4 ,! mass ( a sub/ance deposit$ by an electric curr5t f an electrolyte is proportional to ! int5sity ( curr5t :i* passes ?r\gh x4 ,,ii4 ,! mass ( any sub/ance deposit$ by a curr5t ( uni=m int5sity is directly proportional to ! "t ! curr5t fl[s4 ,^! laws h be5 us$ z a basis = def9+ & measur+ ! unit ( curr5t fl[1 ! amp]e4 7,see ,art4 #bfd47 #bhf4 ,in/ances ( ,electrolysis4--7a7 ,m$ic9es1 especially ^? conta9+ a m9]al sub/ance1 are sometimes introduc$ into ! human body by electrolysis4 7b7 ,wat] & gas pipes are sometimes mu* weak5$ by ! effects ( electric curr5ts 9 ! e>?1 especially return curr5ts f /reet railways4 ,su* curr5ts use ! metal pipes z a conductor4 ,at ! place :]e ! curr5t leaves ! metal & ent]s ! gr\nd1 x removes metallic ions f ! pipe4 ,?is process cont9u+1 ! pipe becomes weak5$ & at l5g? breaks4 7c7 ,copp] is purifi$ by ! use ( electric curr5ts t remove ! copp] f ore or f o!r metals & deposit x ^u electrodes4 ,electrolytic copp] is ! pure/ kn[n4 7d7 ,alum9um is obta9$ by ! use ( l>ge curr5ts ( electricity t fir/ heat ! mat]ial us$ until x melts & !n deposit ! metal f ! fluid mat]ial by electrolysis4 ,^! results are call$ *emical effects ( ! curr5t s9ce by ! use ( electric curr5ts sub/ances are *ang$ *emically1 t is1 !y are sep>at$ into diff]5t *emical sub/ances4 ,important ,topics #a4 ,electrolysis1 electroplat+1 anode1 ca?ode1 ion4 #b4 ,!ory ( electrolysis--evid5ce3 7a7 electrolysis ( wat]2 7b7 conductivity ( acid & wat]4 #c4 ,laws ( electrolysis4 #d4 ,practical use ( electrolysis4 ,ex]cises #a4 ,a dynamo has an ,e4,m4,f4 ( #aj volts4 ,:at is ! resi/ance 9 ! circuit :5 #bj amp]es are fl[+8 #b4 ,h[ mu* silv] w be deposit$ 9 an h\r by ?is curr5t8 #c4 ,"n five objects outside ( ! laboratory t h be5 act$ ^u by electrolysis4 ,h[ 9 ea* case8 #d4 ,:y is table w>e silv] plat$8 ,:y are _m iron objects nickel plat$8 #e4 ,h[ is ! electrolysis ( wat] pipes prev5t$8 #f4 ,two grams ( silv] are to be deposit$ on a spoon by a curr5t ( #a amp]e4 ,f9d ! "t requir$4 #g4 ,h[ long w x take to deposit #bj g4 ( silv] 9 an electroplat+ ba? if a curr5t ( #bj amp]es is us$8 #h4 ,if #ajjj g4 ( silv] are deposit$ on ! ca?ode ( an electrolytic r$uction plant 9 #aj m9utes1 :at is ! curr5t int5sity employ$8 7#b7 ,,! ,,/orage ,,batt]y ,,& ,,electric ,,p[] #bhg4 ,diff]5ces ,betwe5 ,voltaic & ,/orage ,cells4 ,voltaic cells 9 :i* electric curr5ts are produc$ by ! *emical action betwe5 metal plates & an electrolyte are (t5 call$ prim>y batt]ies4 ,9 voltaic cells "o or bo? plates & ! electrolyte are us$ up or lose _! *emical en]gy 9 produc+ ! curr5t & aft] a "t ne$ to be replac$ by new mat]ial1 ! *emical en]gy ( ! electrolyte & ( "o ( ! plates hav+ be5 trans=m$ into electrical en]gy4 ,a diff]5t proce$+ obta9s ) ano!r type ( cell4 ,?is is call$ a /orage batt]y1 or an accumulator4 ,9 ^! cells1 ! same plates & electrolyte are us$ )\t *ange = ext5d$ p]iods1 sometimes = a numb] ( ye>s4 ,= ?is reason /orage batt]ies h displac$ _m o!r types ( cells1 & !y are n[ us$ 7a7 to op]ate _m telephone1 telegraph1 & fire-al>m circuits1 7b7 to "w ! sp>k coils ( gas & gasol9e eng9es1 7c7 to help c>ry ! peak load ^u light+ & p[] circuits & 7d7 to furni% p[] = electric automobiles4 ,s9ce a /orage batt]y c deliv] an electric curr5t only aft] an electric curr5t f an outside s\rce has fir/ be5 s5t ?r\gh x1 !y are (t5 call$ second>y batt]ies4 #bhh4 ,con/ruction & ,action ( a ,/orage ,cell4--,! common type ( /orage cells consi/s ( a numb] ( p]=at$ plates made ( an alloy ( lead & a little antimony4 7,see ,figs4 #bfe1 #bff1 #bfg47 ,into ! p]=ations is press$ a pa/e ( r$ lead & li?>ge mix$ ) sulphuric acid4 ,! plates are plac$ 9 a /rong solution 7#bj to #be p] c5t47 ( sulphuric acid4 ,! plates are n[ ready to be *>g$4 ,?is is accompli%$ by s5d+ a direct curr5t f an electric g5]ator ?r\gh ! cell4 ,! hydrog5 ions are mov$ by ! curr5t to "o set ( plates & *ange ! pa/e to spongy metallic lead4 ,! sulphions move to ! o!r set ( plates & *ange ! pa/e to lead oxide4 ,?is electrolytic action causes ! two plates to become q diff]5t *emically s t :5 ! cell is fully *>g$ x is l a voltaic cell1 9 hav+ plates t are diff]5t *emically4 ,x has1 :5 fully *>g$1 an ,e4,m4,f4 ( ab\t #b4b volts4 ,! sev]al plates ( a cell be+ 9 p>allel & close toge!r1 ! cell has b small int]nal resi/ance4 ,consequ5tly a l>ge curr5t is available4 ,illu/ration3 ,,fig4 #bfe4--,! positive plate ( a /orage cell4 ,illu/ration3 ,,fig4 #bff4--,! negative plate ( a /orage cell4 ,illu/ration3 ,,fig4 #bfg4--;,a complete /orage cell4 ,illu/ration3 ,,fig4 #bfh4 ,ab\t #ge p] c5t4 ( ! en]gy put into ! /orage cell 9 *>g+ c be obta9$ ^u dis*>g+4 ,!re=e ! effici5cy ( a good /orage cell is ab\t #ge p] c5t4 ,fig4 #bfh repres5ts a /orage batt]y connect$ to *>g+ & dis*>g+ circuits4 ,! l[] is ! *>g+ circuit4 ,x conta9s a dynamo & a resi/ance 7nei!r ( :i* are %[n 9 ! figure7 to control ! curr5t s5t into ! cell4 ,! *>g+ curr5t ent]s ! positive pole & leaves by ! negative pole4 ,! curr5t produc$ by ! cell1 h[ev]1 fl[s 9 ! opposite direction ?r\gh x1 t is1 out f ! positive & 9 at ! negative pole4 ,?is curr5t may be controll$ by a suitable resi/ance & measur$ by an ammet]4 ,/orage cells h sev]al advantages3 7a7 ,!y c be *>g$ & dis*>g$ a great _m times be=e ! mat]ial plac$ 9 ! p]=ations 9 ! plates falls out4 7b7 ,! electrical en]gy us$ 9 *>g+ ! plates co/s less ?an ! plates & electrolyte ( voltaic cells4 7c7 ,*>g+ /orage cells takes mu* less labor ?an replac+ ! electrolyte & plates ( voltaic cells4 7d7 ,/orage cells produce l>g] curr5ts ?an voltaic cells4 ,! two pr9cipal disadvantages ( /orage cells are t 7a7 !y are v heavy1 & 7b7 _! initial co/ is consid]able4 ,illu/ration3 ,,fig4 #bfi4--,! ,edison /orage cell4 ,illu/ration3 ,,fig4 #bgj4--,! plates ( ! ,edison /orage cell4 #bhi4 ,! ,edison /orage cell 7,figs4 #bfi & #bgj7 has plates ( iron & nickel oxide4 ,! electrolyte is a /rong solution ( potassium hydroxide4 ,^! cells are light] ?an lead cells ( ! same capacity & !y are claim$ to h a long] life4 #bij4 ,en]gy & ,p[] ( a ,/orage ,cell4--,9 a /orage cell1 ! electrical en]gy ( ! *>g+ curr5t is trans=m$ into *emical en]gy by ! action ( electrolysis4 ,x is ?is *emical en]gy t is trans=m$ into ! en]gy ( ! electric curr5t :5 ! cell is dis*>g$4 ,! capacity ( /orage cells is rat$ 9 amp]e h\rs1 a #dj amp]e h\r cell be+ capable ( produc+ a curr5t ( #a amp]e = #dj h\rs1 or #e amp]es = #h h\rs1 etc4 ,! production & ext5sive use ( electric curr5ts h made necess>y accurate me?ods = measur+ ! en]gy & p[] ( ^! curr5ts4 ,to illu/rate h[ ?is is accompli%$1 let u imag9e an electric circuit z repres5t$ 9 ,fig4 #bfh4 ,"h f\r /orage cells 9 s]ies h an ,e4,m4,f4 ( #h volts & 9 accordance ) ,ohm's law produce a curr5t ( #b amp]es ?r\gh a resi/ance 9 ! circuit ( #d ohms4 ,n[ ! "w done or en]gy exp5d$ by ! curr5t 9 pass+ ?r\gh ! resi/ance betwe5 ! po9ts ,m & ,n dep5ds ^u ?ree factors 7#a7 ! ,e4,m4,f4 or pot5tial diff]5ce2 7#b7 ! curr5t int5sity & 7#c7 ! "t4 ,! en]gy is measur$ by _! product4 ,t is1 electrical en]gy pot5tial diff]5ce curr5t int5sity "t4 ,?is repres5ts ! electrical en]gy 9 j\les1 or ,j\les volts amp]es seconds1 or j ,e ,i t4 ,9 ! circuit repres5t$ 9 ,fig4 #bfh ! en]gy exp5d$ betwe5 ! po9ts ,m & ,n 9 #a m9ute 7#fj seconds7 is #h #b #fj #ifj j\les4 #bia4 ,electric ,p[]4--,s9ce p[] ref]s to ! "t rate at :i* "w is done or en]gy exp5d$1 x may be comput$ by divid+ ! electrical en]gy by ! "t1 or ! electrical p[] volts amp]es4 ,! p[] ( #a j\le p] second is call$ a watt4 ,!re=e1 ,watts volts amp]es1 or ,watts ,e ,i4 ,o!r units ( p[] are ! kil[att #ajjj watts & ! horse-p[] #gdf watts4 ,9 ! example giv5 9 ,art4 #bij ! p[] ( ! curr5t is #h #b #af watts1 or if ! en]gy ( ! curr5t exp5d$ betwe5 ! jo9ts ,m & ,n 7 conv]t$ into me*anical horse-p[] x w\ld equal #af_/gdf ( a horse-p[]4 ,electrical en]gy is usually sold by ! kil[att-h\r1 or ! am\nt ( electrical en]gy t w\ld ex]t a p[] ( #ajjj watts = "o h\r1 or ( #ajj watts = #aj h\rs1 or ( #ej watts = #bj h\rs1 etc4 ,important ,topics #a4 ,! /orage batt]y1 its con/ruction1 electrolyte1 action1 uses1 advantages1 disadvantages4 #b4 ,electric en]gy1 unit value1 h[ comput$8 #c4 ,electric p[]1 ?ree units1 value1 h[ comput$1 h[ sold8 ,ex]cises #a4 ,9 :at ?ree respects are voltaic & /orage cells alike8 ,9 :at two ways diff]5t8 #b4 ,"n ! f\r advantages ( /orage cells 9 ! ord] ( _! importance4 ,give y\r reasons = *oos+ ?is ord]4 #c4 ,:y are dry cells m suitable = op]at+ a door-bell circuit1 ?an a /orage batt]y8 ,give two reasons4 #d4 ,! curr5t = a city telephone sy/em is provid$ by a /orage batt]y4 ,:y is ?is bett] ?an dry cells at ea* telephone8 #e4 ,an inc&esc5t lamp takes #j4e amp]e at #aaj volts4 ,:at p[] is requir$ to op]ate x8 ,h[ mu* en]gy w x trans=m 9 #a m9ute8 #f4 ,h[ long w\ld x take = ?is lamp to use a kil[att h\r ( en]gy8 #g4 ,a /reet c> us$ #ajj amp]es at #fjj volts pressure4 ,:at p[] 0 deliv]$ to x8 ,express also 9 kil[atts & horse-p[]4 #h4 ,an electric toa/] takes #e amp]es at #aaj volts4 ,if x toa/s a slice ( bread 9 #b m9utes1 :at is ! co/ at #aj c5ts a kil[att h\r8 #i4 ,an electric flat iron takes #e amp]es at #aaj volts4 ,f9d ! co/ ( us+ x = #b h\rs at #ab c5ts a kil[att h\r4 #aj4 ,a #a_/d kil[att motor is us$ to run a wa%+-ma*9e = #e h\rs4 ,:at is ! exp5se = ?is p[] at #aj c5ts a kil[att h\r8 #aa4 ,:at is ! effici5cy ( a motor t takes #gcij watts & develops #i horse-p[]8 #ab4 ,h[ _m horse-p[] are !re 9 a wat]-fall #bab ft4 high ov] :i* fl[s #hjj cu4 ft4 ( wat] p] second8 ,express ?is p[] 9 kil[atts4 #ac4 ,:at horse-p[] mu/ be appli$ to a dynamo hav+ an effici5cy ( g p] c5t4 if x is to light #bj arc lamps 9 s]ies1 ea* tak+ #aj amp]es at #fj volts8 7#c7 ,,! ,,heat ,,effect ,,( ,,electric ,,curr5ts #bib4 ,! ,production ( ,heat by an ,electric ,curr5t4--,:5 no *emical or me*anical "w is done by an electric curr5t its en]gy is employ$ 9 ov]com+ ! resi/ance ( ! conduct+ circuit & is trans=m$ into heat4 ,?is effect has _m practical applications & "s disadvantages4 ,_m devices employ ! heat+ effect ( electric curr5ts1 7a7 ! electric furnace1 7b7 electric lights1 7c7 heat+ coils = /reet c>s1 7d7 devices ab\t ! home1 z flat irons1 toa/]s1 etc4 ,sometimes ! heat produc$ by an electric curr5t 9 ! wires ( a device su* z a trans=m] is s l>ge 9 am\nt t especial means ( cool+ are employ$4 ,unusually heavy curr5ts h be5 kn[n to melt ! conduct+ wires ( circuits & electrical devices4 ,h5ce all circuits = electric p[] z well z _m o!rs t ord9>ily c>ry small curr5ts are protect$ by fuses4 ,an electric fuse is a %ort piece ( wire t w melt & break ! circuit if ! curr5t exce$s a det]m9$ value4 ,! fuse wire is usually enclos$ 9 an incombu/ible hold]4 ,fuse wire is frequ5tly made ( lead or ( an alloy ( lead & o!r easily fusible metals4 7,see ,figs4 #bga & #bgb47 ,illu/ration3 ,,fig4 #bga4--;,a type ( enclos$ fuse4 ,illu/ration3 ,,fig4 #bgb4--;,a l9k fuse 7above72 plug fuses 7bel[74 #bic4 ,heat ,develop$ 9 a ,conductor4--,a rule = comput+ ! am\nt ( heat produc$ 9 an electric circuit by a giv5 curr5t has be5 accurately det]m9$ by exp]im5t4 ,x has be5 f\nd t #a calorie ( heat 7,art4 #adb71 is produc$ by an exp5diture ( #d4b j\les ( electrical 7or o!r7 en]gy4 ,9 o!r words1 #a j\le w produce #a_/d4b or #j4bd calorie4 ,n[ ! numb] ( j\les ( electrical en]gy 9 an electric circuit is express$ by ! foll[+ =mula3 ,j\les volts amp]es seconds1 or s9ce #a j\le #j4bd calorie1 ,calories volts amp]es seconds #j4bd or ,h ,,ei t #j4bd 7#a7 ,by ,ohm's law1 ,i ,e_/,r or ,e ,i ,r1 sub/itut+ 9 equation 7#a7 ,,ir = its equal ,e we h ,h ,i,r t #j4bd 7#b7 ,also s9ce ,i ,e_/,r sub/itute ,e_/,r = ,i 9 equation 7#a7 & we h ,h ,e_/,r t #j4bd 7#c7 ,to illu/rate ! use ( ^! =mulas by a problem suppose t a curr5t ( #aj amp]es is fl[+ 9 a circuit hav+ a resi/ance ( #aa ohms1 = #a m9ute4 ,! heat produc$ w be by =mula 7#b7 7#aj7 #aa #fj #j4bd equals #ae1hdj calories4 ,illu/ration3 ,,fig4 #bgc4--;,a c>bon filam5t inc&esc5t lamp4 ,illu/ration3 ,,fig4 #bgd4--;,a tung/5 lamp4 #bid4 ,! ,inc&esc5t ,lamp4--,"o ( ! mo/ common devices employ+ ! heat effect ( an electric curr5t is ! inc&esc5t lamp4 7,see ,fig4 #bgc47 ,9 ?is lamp ! curr5t is s5t ?r\gh a c>bon filam5t1 :i* is heat$ to inc&esc5ce4 ,9 ord] to keep ! filam5t f burn+ z well z to prev5t loss ( heat by convection1 x is plac$ 9 a glass bulb f :i* ! air is exhau/$4 ,two plat9um wires fus$ 9 ! glass connect ! c>bon filam5t ) ! groov$ rim & ! end piece ( ! base4 ,! end piece & rim connect ) ! socket s t an electric curr5t may fl[ ?r\gh ! filam5t ( ! lamp4 ,! c>bon inc&esc5t lamp has a l[ effici5cy4 ,x takes #j4e amp]e ( curr5t at #aaj volts or 9 o!r words x requires #ee watts to cause a #af-;c&le-p[] lamp to gl[ brightly1 h5ce #a c&le p[] 9 ?is lamp takes #ee_/af #c4dc watts4 ,! effici5cy ( electric lamps is measur$ by ! numb] ( watts p] c&le p[]4 ,?is is a peculi> use ( ! t]m effici5cy1 z ! l>g] ! numb] ! less effici5t is ! lamp4 ,m effici5t lamps h be5 devis$ ) filam5ts ( ! metals tantalum & tung/5 7,fig4 #bgd74 ,^! give a :it] light ?an d c>bon lamps1 & consume b ab\t #a4be watts p] c&le p[]4 ,,comp>ative ,,effici5cy ,,( ,,electric ,,lamps ---------------------------------------- ---------------- ,watts p] ,watts p] ,"n ( lamp c&le ,"n ( lamp c&le p[] p[] ---------------------------------------- ---------------- ,c>bon filam5t #c to #d ,arc lamp #j4e to #j4h ,metalliz$ c>bon #b4e ,m]cury arc #j4f ,tantalum #b4j ,flam+ arc #j4d ,tung/5 #a4j to ,nitrog5-fill$ #j4f to #j4g #a4e tung/5 ---------------------------------------- ---------------- ,inc&esc5t lamps are connect$ 9 p>allel 7see ,fig4 #bed7 to wires t are kept at a con/ant diff]5ce ( pot5tial ( #aaj or #aae volts4 ,x is cu/om>y to place n m ?an twelve lamps ^u "o circuit1 ea* circuit be+ protect$ by a fuse & controll$ by "o or m swit*es4 #bie4 ,! ,arc ,light4--,! electric arc light 7see ,fig4 #bge7 is ext5sively us$ = light+ l>ge rooms1 also 9 /]eopticons & motion picture ma*9es4 ,! light is int5se1 v>y+ f #ejj to #agjj c&le p[]4 ,! s-call$ mean sph]ical c&le p[] ( ! arc light is ab\t #eaj4 ,! c&le p[] 9 ! direction ( greate/ int5sity is ab\t #abjj4 ,x is produc$ at an exp5diture ( ab\t #ejj watts4 ,x is !re=e m effici5t ?an ! inc&esc5t lamp1 (t5 tak+ less ?an #j4e watt p] c&le p[] produc$4 ,! arc light 0 fir/ devis$ by ,sir ,humphrey ,davy 9 #ahji1 :o us$ two pieces ( *>coal connect$ to #bjjj voltaic cells4 ,! arc light requires s mu* p[] t its production by voltaic cells is v exp5sive4 ,consequ5tly x did n come into common use until ! dynamo _h be5 p]fect$4 ,fig4 #bgf %[s ! appe>ance ( ! two c>bons 9 an arc light4 ,if a direct curr5t is us$ ! positive c>bon is heat$ m int5sely1 & gives out ! great] "p ( ! light4 ,! positive c>bon is consum$ ab\t twice z fa/ z ! negative & its end is concave1 ! negative rema9+ po9t$4 ,illu/ration3 ,,fig4 #bge4--;,an electric arc light4 ,illu/ration3 ,,fig4 #bgf4--,! appe>ance ( a pair ( us$ c>bons4 ,) alt]nat+ curr5ts1 ! rods are equally consum$ & produce equal am\nts ( light4 ,9 ! /]eopticon1 ! c>bons are usually plac$ at "r angles z 9 ,fig4 #bgg4 ,9 ! /]eopticon z well z 9 outdoor light+ ! direct curr5t is m effective1 al?\gh ! alt]nat+ curr5t is (t5 us$1 s9ce ! latt] c be produc$ & di/ribut$ m *eaply ?an c direct curr5ts4 ,9 arc lamps1 plac+ an inn] glass globe 7,fig4 #bgh7 ab\t ! c>bons1 decreases ! consumption ( ! c>bons mat]ially4 ,! c>bon rods ( enclos$ arc lamps (t5 la/ #fj to #ajj h\rs4 ,illu/ration3 ,,fig4 #bgg4--;,a "r-angle electric arc lamp = a /]eopticon4 ,illu/ration3 ,,fig4 #bgh4--;,an enclos$ arc lamp4 ,! reason :y an op5 arc lamp ne$s to be retrimm$ (t5] ?an ! enclos$ lamp1 t is1 h new c>bons plac$ 9 x1 is because ! c>bons burn freely1 t is unite ) ! oxyg5 ( ! air4 ,9 ! enclos$ arc lamp1 ! supply ( oxyg5 9 ! inn] globe is limit$ & is soon consum$1 !re=e ! c>bons la/ _m times long] 9 su* lamps4 ,"s c>bon rods h s(t cores conta9+ calcium salts4 ,^! vaporize 9 ! arc produc+ ! flam+ arc light ( a bright yell[ color1 & give m light ?an ! ord9>y lamp4 ,important ,topics #a4 ,heat effects ( electric curr5ts1 uses & applications4 #b4 ,computation ( ! heat develop$ 9 a circuit4 ,?ree =mulas4 #c4 ,electric lamps2 inc&esc5t & arc2 con/ruction1 uses1 effici5cy4 ,ex]cises #a4 ,sket* a circuit conta9+ #aj inc&esc5t lamps 9 p>allel4 ,if ea* lamp :5 hot has a resi/ance ( #bbj ohms1 & ! ,e4,m4,f4 is #ajj volts1 :at curr5t w fl[8 #b4 ,:at w x co/ to use ^! lights = #c h\rs a day = #cj days at #aj c5ts a kil[att h\r8 #c4 ,h[ mu* heat w ^! lamps produce p] m9ute8 #d4 ,h[ c\ld y connect #aaj-volt lamps to a /reet c> circuit ( #ffj volts8 ,expla9 ?is arrangem5t & draw a diagram4 #e4 ,a c]ta9 arc lamp requir$ #aj amp]es ( curr5t at #de volts pressure4 ,:at w\ld x co/ at #aj c5ts p] kil[att h\r if us$ #c h\rs a day = #cj days8 #f4 ,%[ a diagram ( #c arc lamps 9 s]ies4 ,if ea* takes #de volts & #aj amp]es1 h[ mu* ,e4,m4,f4 & curr5t w !y require8 #g4 ,if an electric toa/] uses #e amp]es at #aae volts1 h[ mu* heat w ?is develop 9 half an h\r8 #i4 ,h[ mu* heat is develop$ 9 an electric toa/] 9 #b m9utes1 if x uses #e amp]es at #ajj volts8 #aj4 ,h[ _m ,b4t4u4's are giv5 (f 9 an electric ov5 t takes #aj amp]es at #aaj volts = #a h\r8 7#a ,b4t4u4 equals #beb calories47 #aa4 ,an electric heat] supplies heat at ! rate ( #gjj ,b4t4u4's an h\r4 ,h[ mu* p[] does x require8 #ab4 ,h[ _m watts are requir$ to op]ate #abj inc&esc5t lamps 9 p>allel if ea* takes #j4e amp]es at #aaj volts8 #ac4 ,an electric lamp takes #ab amp]es at a ,p4,d4 ( #aaj volts4 ,h[ _m ,b4t4u4's are radiat$ f x ea* second8 ,h[ _m calories8 #ad4 ,if a #aaj-volt inc&esc5t lamp is subm]g$ = #aj m9utes 9 #djj gr4 ( cold wat] :ile a curr5t ( #j4e amp]es is fl[+1 h[ _m degrees c5tigrade w ! wat] be w>m$8 #ae4 ,9 an electric furnace a curr5t ( #cjjj amp]es is us$ at a ,p4,d4 ( #aj volts4 ,f9d ! heat develop$ 9 #a m9ute4 #af4 ,h[ _m c&le p[] %\ld a #bj-watt tung/5 lamp give if its effici5cy is "o watt p] c&le p[]8 #ag4 ,:at is ! effici5cy ( a #dj-watt tung/5 lamp if x gives #cd c&le p[]8 ,review ,outl9e3 ,curr5t ,electricity ,produc$ by--,*emical action2 voltaic & /orage cells4 ,?ree ,magnetic1 electromagnet1 uses & applications4 ,pr9cipal ,*emical1 electrolysis1 applications4 ,effects3 ,heat1 light+ & heat+ devices4 ,!ories3 7a7 ( voltaic cells1 7b7 ( electrolysis4 ,units3 ,amp]e1 ohm1 volt1 watt1 j\le1 kil[att1 horse p[]4 ,measurem5t--7a7 magnetic effect2 galvanomet]1 ammet]1 voltmet]1 wattmet]1 ,:eat/one bridge1 con/ruction & use4 7b7 *emical effect2 voltamet]4 ,laws3 7a7 ,"r h& rules1 = conductor & helix4 7b7 ,resi/ance1 ,conductors 9 s]ies & p>allel4 7c7 ,ohm's law1 heat law1 p[] law1 #c =ms = ea*4 7d7 ,cells 9 p>allel & s]ies4 ,problems3 ,^u applications ( ! laws & =mulas /udi$4 ,devices4 ,voltaic cells2 wet1 dry1 & ,daniell4 & ,electrolysis & ! /orage batt]y4 ,in/rum5ts3 ,measur+ in/rum5ts1 electric bell1 s\nd]1 heat+ & light+ devices4 ,t]ms3 ,anode1 ca?ode1 electrolyte1 ion1 circuit swit*1 curr5t1 e4m4f41 resi/ance1 pot5tial4 ,,*apt] ,,xiv ,,induc$ ,,curr5ts 7#a7 ,,electromagnetic ,,induction #bif4 ,curr5t ,induc$ by a ,magnet4--,! discov]y 9 #ahai t a curr5t 9 a conductor c deflect a magnetic ne$le or t x has a magnetic effect1 l$ to _m attempts to produce an electric curr5t by means ( a magnet4 ,x 0 n until ab\t #ahca1 h[ev]1 t ,joseph ,h5ry 9 ,am]ica & ,mi*ael ,f>aday 9 ,engl&1 indep5d5tly discov]$ h[ to accompli% ?is important result4 ,at ! pres5t "t1 voltaic cells produce b a v small "p ( ! curr5t electricity us$4 ,practically all t is employ$ = p[]1 light1 heat1 & electrolysis is produc$ by ! use ( magnetic fields1 or by electromagnetic induction4 #big4 ,laws ( ,induc$ ,curr5ts4,m--,to illu/rate h[ a curr5t c be produc$ by electromagnetic induction3 ,m ,an induc$ curr5t is "o produc$ by *ang+ ! numb] ( magnetic l9es ( =ce pass+ ?r\gh a coil4 ,connect a coil ( #djj or m turns ( ,no4 #bb insulat$ copp] wire to a s5sitive galvanomet]4 7,see ,fig4 #bgi47 ,n[ ins]t a b> magnet 9 ! coil4 ,a sudd5 movem5t ( ! galvanomet] w be notic$1 indicat+ ! production ( a curr5t4 ,:5 ! magnet /ops mov+1 h[ev]1 ! curr5t /ops1 & ! coil ( ! galvanomet] returns to its fir/ position4 ,if n[ ! magnet is remov$1 a movem5t ( ! galvanomet] coil 9 ! opposite direction is notic$4 ,?is action may be repeat$ z (t5 z desir$ ) simil> results4 ,c>eful exp]im5ts h %[n t x is ! magnetic field ( ! magnet t produces ! action1 & t only :5 ! numb] ( l9es ( =ce 9 ! coil is *ang+ d we f9d a curr5t produc$ 9 ! coil4 ,^! facts lead to ,law ,i4 ,any *ange 9 ! numb] ( magnetic l9es ( =ce pass+ ?r\gh or cut by a coil w produce an electromotive =ce 9 ! coil4 ,9 ! acc\nt ( ! exp]im5t j giv51 electric curr5ts are produc$1 :ile 9 ,law ,i1 electromotive =ces are m5tion$4 ,?is diff]5ce is due to ! fact t an ,e4,m4,f4 is always produc$ 9 a coil :5 ! magnetic field )9 x is *ang$1 :ile a curr5t is f\nd only :5 ! coil is "p ( a clos$ circuit4 ,! inductive action ( ! e>?'s magnetic field 7see ,fig4 #bhj71 may be %[n by means ( a coil ( #djj to #ejj turns a foot 9 diamet]4 ,illu/ration3 ,,fig4 #bgi4--,! mov+ magnet induces a curr5t 9 ! coil4 ,illu/ration3 ,,fig4 #bhj4--;,a curr5t may be induc$ by turn+ ! coil 9 ! e>?'s magnetic field4 ,connect its ends to a s5sitive galvanomet] & hold x at "r angles to ! e>?'s field4 ,!n quickly revolve ! coil ?r\gh #ahj degrees & note ! movem5t ( ! galvanomet]4 ,rev]se ! coil & ! galvanomet] sw+s 9 ! opposite direction4 ,if ! magnet 9 ,fig4 #bgi is mov$ 9 & out ( ! coil at fir/ sl[ly & lat] swiftly1 small & l>ge deflections ( ! galvanomet] coil are notic$4 ,! quick] ! movem5t ( ! magnetic field ! great] are ! galvanomet] deflections produc$4 ,?is leads to ,law ,,ii4 ,! electromotive =ces produc$ are proportional to ! numb] ( l9es ( =ce cut p] second4 #bih4 ,! magneto is a device t illu/rates ! laws ( induc$ curr5ts /at$ 9 ,art4 #big4 ,! magneto 7see ,fig4 #bha71 consi/s ( sev]al p]man5t1 ,u-%ap$ magnets plac$ side by side4 ,betwe5 ! poles ( ^! magnets is plac$ a slott$ iron cyl9d] hav+ a coil ( _m turns ( f9e insulat$ copp] wire w\nd 9 ! slot z 9 ,fig4 #bhb4 ,! cyl9d] & coil =m :at is call$ an armature4 ,! armature is m\nt$ s z to be revolv$ betwe5 ! poles ( ! ,u-%ap$ magnets by means ( a h&le4 ,z ! armature revolves1 ! l9es ( =ce f ! magnets pass ?r\gh ! coil fir/ 9 "o direction & !n 9 ! o!r4 ,?is repeat$ *ange 9 ! l9es ( =ce pass+ ?r\gh ! coil produces an ,e4,m4,f4 :i* may be felt by hold+ 9 ! h&s ! two wires lead+ f ! armature coil4 ,on turn+ ! armature fa/] ! curr5t is felt mu* /rong]1 %[+ t ! ,e4,m4,f4 9 ! coil increases z ! rate ( cutt+ ! magnetic l9es ( =ce by ! coils increases4 ,illu/ration3 ,,fig4 #bha4--;,a magneto4 ,illu/ration3 ,,fig4 #bhb4--;,a %uttle armature4 ,illu/ration3 ,,fig4 #bhc4--,! induc$ curr5t has a field :i* opposes ! motion ( ! magnet4 ,! heavy l9e repres5ts ! direction ( ! induc$ curr5t4 #bii4 ,l5z's ,law4--,:ile "o is turn+ ! armature ( a magneto if ! two wires lead+ f its coil are connect$1 =m+ :at is call$ a %ort circuit1 ! difficulty ( turn+ ! armature is at once increas$4 ,if n[ ! circuit is brok51 ! armature turns z easily z at fir/4 ,! increas$ difficulty 9 turn+ ! armature is due to ! curr5t produc$ 9 ! coil4 ,?is curr5t sets up a magnetic field ( its own t opposes ! field f ! /eel magnets4 ,?is opposition makes x necess>y = "w to be done to keep up ! motion ( ! coil :5 a curr5t is pass+ ?r\gh x4 ,?is fact is call$ ,l5z's ,law4 ,x may be express$ z foll[s3 ,:5ev] a curr5t is induc$ by ! relative motion ( a magnetic field & a conductor1 ! direction ( ! induc$ curr5t is always su* z to set up a magnetic field t opposes ! motion4 ,l5z's ,law foll[s f ! pr9ciple ( cons]vation ( en]gy1 t en]gy c be produc$ only f an exp5diture ( o!r en]gy4 ,n[ s9ce an electric curr5t possesses en]gy1 su* a curr5t c be produc$ only by do+ me*anical "w or by exp5d+ "s o!r =m ( en]gy4 ,to illu/rate ,l5z's ,law1 suppose t ! nor?-seek+ pole ( a b> magnet be ins]t$ 9 a clos$ coil ( wire4 7,see ,fig4 #bhc47 ,! curr5t induc$ 9 ! coil has a direction su* t its l9es ( =ce w pass )9 ! coil s z to oppose ! field ( ! b> magnet1 :5 ! nor? pole ( ! magnet is ins]t$ s z to po9t to ! left4 ,t is1 ! nor? pole ( ! helix is at ! "r4 ,apply+ ! "r-h& rule to ! coil1 its curr5t w !n be c\nt] clockwise4 ,on )draw+ ! magnet1 ! curr5t rev]ses1 becom+ clockwise ) its field pass+ to ! left )9 ! coil4 ,a /rik+ illu/ration ( ! opposition (f]$ by ! field ( ! induc$ curr5t to t ( ! induc+ field is af=d$ by tak+ a /rong electromagnet 7see ,fig4 #bhd7 & susp5d+ a %eet ( copp] s z to sw+ freely betwe5 ! poles4 ,:5 no curr5t fl[s ?r\gh ! magnet ! %eet sw+s easily = "s "t4 ,:51 h[ev]1 ! coils are magnetiz$1 ! copp] %eet has induc$ )9 x1 curr5ts t set up magnetic fields /rongly oppos+ ! motion1 ! sw++ be+ /opp$ almo/ in/antly4 ,! pr9ciple is appli$ 9 good ammet]s & voltmet]s to prev5t ! sw++ ( ! ne$le :5 deflect$4 ,! curr5t induc$ 9 ! metal =m on :i* is w\nd ! galvanomet] coil is suffici5t to make ! ne$le practically dead beat4 ,illu/ration3 ,,fig4 #bhd4--,! magnetic field /ops ! sw++ ( ! %eet ( copp]4 #cjj4 ,! ,magneto & ! ,dynamo4--,magnetos are us$ to develop small curr5ts1 su* z are us$ = telephone signals1 & = op]at+ ! sp>k+ devices ( gasol9e eng9es4 ,!y are !re=e f\nd 9 automobiles conta9+ gasol9e motors4 ,! mo/ important device = produc+ electric curr5ts by electromagnetic induction1 h[ev]1 is ! dynamo4 ,x is employ$ :5ev] l>ge curr5ts are desir$4 ,! pr9ciple ( ?is device is simil> to t ( ! magneto except t x conta9s an electromagnet = produc+ ! magnetic field4 ,s9ce ! electromagnet c develop a mu* /rong] field ?an a p]man5t magnet1 ! dynamo c produce a high] ,e4,m4,f4 & a mu* l>g] curr5t ?an ! magneto4 ,illu/ration3 ,,"l ,,kelv9 ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,"l ,kelv9 7,sir ,william ,?omson71 7#ahbd-aijg74 ,pr(essor ( ,physics1 ,glasg[ ,univ]sity4 ,inv5t$ ! absolute scale ( temp]ature3 also _m practical electrical measur+ in/rum5ts4 ,! =emo/ physici/ ( ! latt] "p ( ! n9ete5? c5tury4 ,illu/ration3 ,,mi*ael ,,f>aday ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,mi*ael ,f>aday 7#agia-ahfg74 ,fam\s ,engli% ,physici/4 ,made _m discov]ies 9 electricity & magnetism2 ,greate/ exp]im5tali/ ( ! n9ete5? c5tury4 #cja4 ,! ,magnetic ,fields ( ,g5]ators4--,9 ! magneto1 ! magnetic field is produc$ by p]man5t /eel magnets4 ,9 dynamos p[]ful electromagnets are us$4 ,! latt] are sometimes excit$ by curr5ts f "s o!r s\rce1 b usually curr5t f ! armature is s5t ar\nd ! field coils to produce ! magnetic fields4 ,dynamos are classifi$ accord+ to ! mann] 9 :i* ! curr5t is s5t to _! field coils4 ,illu/ration3 ,,fig4 #bhe4--;,a s]ies-w\nd dynamo4 ,illu/ration3 ,,fig4 #bhf4--;,a %unt-w\nd dynamo4 ,illu/ration3 ,,fig4 #bhg4--;,a comp\nd-w\nd dynamo4 ,a4 ,! s]ies w\nd dynamo 7see ,fig4 #bhe7 is arrang$ s t all ( ! curr5t produc$ by ! armature is s5t ?r\gh coils ( co>se wire ^u ! fields1 aft] fl[+ ?r\gh ! ext]nal circuit4 ,b4 ,! %unt w\nd dynamo 7see ,fig4 #bhf7 s5ds a "p only ( ! curr5t produc$ ?r\gh ! field coils4 ,! latt] are ( _m turns ( f9e wire s z to use z little curr5t z possible4 ,! great] "p ( ! curr5t goes to ! ma9 circuit4 ,if ! numb] ( lamps or motors connect$ to ! ma9 circuit is increas$1 ! voltage is less5$ :i* weak5s ! curr5t 9 ! field coils1 caus+ a weak] field & /ill l[] voltage1 produc+ a fluctuat+ ,e4,m4,f4 :i* is unsatisfactory = _m purposes4 ,?is fault is ov]come by ,c4 ! comp\nd w\nd dynamo4 ,?is dynamo has bo? %unt & s]ies coils ^u its fields4 7,see ,fig4 #bhg47 ,if m curr5t is drawn into ! ma9 circuit ) ?is dynamo1 ! s]ies coils produce a /rong] field comp5sat+ = ! weak] field ( ! %unt coils1 s t uni=m voltage is ma9ta9$4 ,! comp\nd w\nd g5]ator is !re=e ! "o mo/ commonly employ$4 ,important ,topics #a4 ,laws ( electromagnetic induction 7a7 conditions1 7b7 ,e4,m4,f41 7c7 direction4 #b4 ,devices1 7a7 magneto1 7b7 dynamo3 s]ies1 %unt1 comp\nd4 #c4 ,illu/rations ( ! laws4 ,ex]cises #a4 ,"u :at conditions may an electric curr5t be produc$ by a magnet8 #b4 ,%[ h[ ,l5z's ,law1 foll[s f ! pr9ciple ( cons]vation ( en]gy4 #c4 ,a b> magnet is fix$ upright ) its nor?-seek+ pole upw>d4 ,a coil is ?ru/ d[n ov] ! magnet4 ,:at is ! direction ( ! curr5t induc$ 9 ! coil8 ,expla94 #d4 ,9 :at two ways may a curr5t be induc$ 9 a clos$ coil8 #e4 ,:at me?od is employ$ 9 ! magneto8 ,9 ! dynamo8 #f4 ,:at is ! nature ( ! curr5t produc$ 9 ! armature coil ( a magneto1 t is1 is x direct or alt]nat+8 ,:y8 #g4 ,:at is ! resi/ance ( a #bj-watt tung/5 lamp if ! ,e4,m4,f4 is #aae volts8 #h4 ,f9d ! resi/ance ( a #dj-watt tung/5 lamp :5 ! voltage is #aae8 ,h[ mu* heat w x produce p] m9ute8 #i4 ,an ,edison /orage batt]y cell on a te/ gave a dis*>ge ( #cj amp]es4 ,! av]age voltage 0 #a4ai4 ,:at 0 ! resi/ance ( ! cell8 #aj4 ,eight /orage cells are connect$ 9 s]ies4 ,ea* has an ,e4,m4,f4 ( #a4b volts & an int]nal resi/ance ( #j4jc ohms4 ,:at w be ! curr5t fl[+ ?r\gh a voltmet] hav+ #ejj ohms resi/ance 9 circuit ) !m8 7#b7 ,,! ,,dynamo ,,& ,,! ,,motor #cjb4 ,! ,dynamo may be def9$ z a ma*9e = trans=m+ me*anical en]gy into ! en]gy ( electric curr5ts by electromagnetic induction4 ,al?\gh electromagnetic induction 0 discov]$ 9 #ahba1 practical dynamos 7 n built = ab\t #dj ye>s or until betwe5 #ahfj & #ahgj4 ,! great developm5t 9 ! production & use ( electric curr5ts has come s9ce ! latt] date4 ,! pr9ciple p>ts ( ! dynamo are 7a7 ! field magnet1 7b7 ! armature1 7c7 ! commutator or collect+ r+s1 7d7 ! bru%es4 ,fig4 #bhh %[s sev]al common me?ods ( arrang+ ! field coils & ! armature4 ,illu/ration3 ,,fig4 #bhh4--,sev]al me?ods ( arrang+ ! field coils & ! armature ( a dynamo4 ,illu/ration3 ,,fig4 #bhi4--;,a drum armature4 ,! field coils v>y 9 numb] & position4 ,! purpose ( _! con/ruction is always to s5d ! l>ge/ possible numb] ( l9es ( =ce ?r\gh ! armature4 ,"s dynamos are bipol>1 or h two poles1 o!rs are multipol> or h m ?an two4 ,9 ,fig4 #bhh ,no4 #d has f\r poles4 ,! armature ( a dynamo diff]s f a magneto armature 9 t x consi/s ( a s]ies ( coils ( insulat$ copp] wire w\nd 9 num]\s slots cut 9 ! surface ( a cyl9drical piece ( iron4 ,fig4 #bhi %[s a side view ( ! iron core ( su* an armature4 ,iron is us$ to =m ! body ( ! armature s9ce ! magnetic l9es ( =ce fl[ easily ?r\gh ! iron4 ,! iron by its p]meability also conc5trates & increases ! magnetic flux4 ,! be/ armatures are made ( _m ?9 %eets ( s(t iron4 ,^! are call$ lam9at$ armatures4 ,an armature made ( a solid piece ( iron becomes hot :5 revolv+ 9 a magnetic field4 ,?is is due to electric curr5ts induc$ 9 ! iron itself4 ,?is heat+ is l>gely r$uc$ by lam9at+ ! armature4 ,:y8 ,illu/ration3 ,,fig4 #bij4--;,armature connect$ to slip r+s produc+ an alt]nat+ curr5t4 #cjc4 ,me?ods ( ,collect+ ,curr5t f ! ,armature4--,! electric curr5ts produc$ 9 ! armature are conduct$ away by special slid+ contacts4 ,! /ation>y "p ( ! slid+ contact is call$ a bru%4 ,! mov+ "p is a slip r+ or a commutator4 ,fig4 #bij %[s an armature coil connect$ to slip r+s4 ,z ! armature revolves1 ! coils & slip r+s revolve ) x4 ,! two ends ( ! armature coils are connect$ to ! two r+s respectively4 ,n[ z ! armature revolves x cuts ! l9es ( =ce fir/ 9 "o direction & !n 9 ! o!r4 ,?is produces 9 ! coils an ,e4,m4,f4 fir/ "o way & !n ! o!r4 ,?is ,e4,m4,f4 sets up a curr5t :i* is conduct$ to ! outside circuits ?r\gh ! slip r+s & bru%es4 ,su* a curr5t :i* repeat$ly rev]ses its direction is call$ an alt]nat+ curr5t4 ,fig4 #bia 7#a7 indicates graphically h[ ! curr5t moves alt]nately "o way & !n ! o!r4 ,alt]nat+ curr5ts are ext5sively us$ = electric light1 heat1 & p[]4 ,direct curr5ts or ^? go+ cont9u\sly 9 "o direction are h[ev] 9 mu* dem& especially = /reet c> s]vice1 = electrolysis1 & = *>g+ /orage batt]ies4 #cjd4 ,! ,commutator4--,= a dynamo to deliv] a direct curr5t x mu/ c>ry ^u ! %aft ( ! armature a commutator4 ,! commutator is us$ to rev]se ! connections ( ! ends ( ! armature coils at ! in/ant t ! curr5t *anges its direction 9 ! armature4 ,?is rev]sal ( connection :5 ! direction ( curr5t *anges1 keeps ! curr5t 9 ! outside circuit fl[+ 9 ! same direction4 ,fig4 #bia is a diagram ( an armature ) a commutator4 ,! commutator is a split r+1 hav+ z _m p>ts or segm5ts z !re are coils ^u ! armature4 ,! bru%es t\* opposite po9ts ^u ! commutator z !y slide ov] ! surface ( ! latt]4 ,suppose t ! armature view$ f ! commutator end rotates 9 a c\nt]-clockwise direction1 also t ! curr5ts f ! upp] "p move t[>d ! commutator & out ! top bru%4 ,illu/ration3 ,,fig4 #bia4--,! armature coils are connect$ to a commutator produc+ a direct curr5t4 ,z ! armature revolves1 its coils soon beg9 to cut ! =ce l9es 9 ! opposite direction4 ,?is *ange 9 ! direction ( cutt+ ! l9es ( =ce causes ! curr5t to rev]se 9 ! coils ( ! armature4 ,at ! in/ant ! curr5t *anges 9 direction1 :at 0 ! upp] segm5t ( ! commutator slips ov] into contact ) ! l[] bru%1 & ! o!r segm5t sw+s ov] to t\* ! upp] bru%4 ,s9ce ! curr5t has rev]s$ 9 ! coils x cont9ues to fl[ out ( ! upp] bru%4 ,?is *ange 9 connection at ! bru%es takes place at ea* half turn ( ! armature1 j z ! curr5t *anges 9 direction 9 ! coils4 ,?is is ! mann] 9 :i* ! commutator ( a dynamo *anges ! alt]nat+ curr5t produc$ 9 ! armature coils1 into a direct curr5t 9 ! ext]nal circuit4 ,fig4 #bib 7#a7 repres5ts graphically an alt]nat+ curr5t1 7#b7 ( ! same figure %[s curr5t tak5 f ! bru%es ( ! commutator ( a dynamo ) "o coil on ! armature4 ,illu/ration3 ,,fig4 #bib4--;,graphic repres5tation ( 7#a7 an alt]nat+ curr5t2 7#b7 a pulsat+ curr5t2 7#c7 a cont9u\s curr5t4 ,illu/ration3 ,,fig4 #bic4--;,de,laval multi-/age turb9e & ge> driv+ #gej-kw41 #gej-r4p4m41 #fjj-volt direct-curr5t g5]ator4 ,a practical dynamo1 h[ev]1 has _m coils ^u its armature ) a correspond+ numb] ( segm5ts ^u ! commutator4 7,see ,figs4 #bhi & #bic47 ,z ea* coil & commutator segm5t passes a bru%1 x contributes an impulse to ! curr5t ) ! result t armatures ) _m coils produce curr5ts t fl[ q ev5ly4 7,see ,fig4 #bib1 #c47 ,! curr5t repres5t$ 9 ,fig4 #bib 7#b7 is call$ a pulsat+ curr5t4 ,illu/ration3 ,,fig4 #bid4--;,a wire c>ry+ a curr5t across a magnetic field is pu%$ sideways by ! field4 #cje4 ,! electric motor is a ma*9e :i* trans=ms ! en]gy ( an electric curr5t into me*anical en]gy or motion4 ,! direct curr5t motor consi/s ( ! same ess5tial p>ts z a direct curr5t dynamo1 viz41 ! field magnet1 armature1 commutator & bru%es4 ,its op]ation is readily compreh5d$ aft] "o und]/&s ! foll[+ exp]im5t3 ,set up two b> electromagnets ) unlike poles fac+ ea* o!r ab\t an in* ap>t4 ,a wire connect$ to a s\rce ( curr5t is hung loosely betwe5 ! poles z 9 ,fig4 #bid4 ,! circuit ?r\gh ! wire %\ld conta9 a key or swit*4 ,if a curr5t is s5t ?r\gh ! electromagnets & !n ano!r is s5t ?r\gh ! wire1 ! latt] w be f\nd to be pu%$ ei!r up or d[n1 :ile if ! curr5t is rev]s$ ?r\gh ! wire x is pu%$ 9 ! opposite direction4 ,^! results may be expla9$ z foll[s3 ,consid] ! magnetic field ab\t a wire c>ry+ a curr5t 7,see ,fig4 #bie47 ,if su* a wire is plac$ 9 ! magnetic field betwe5 two opposite poles ( an electromagnet 7,fig4 #bif71 ! wire w be mov$ ei!r up or d[n4 ,! reason = ?is is %[n by ! diagram 9 ,fig4 #big4 ,"h a wire c>ry+ a curr5t & !re=e surr\nd$ by a magnetic field passes across ano!r magnetic field4 ,! two fields affect ea* o!r caus+ a cr[d+ ( ! =ce l9es ei!r above or bel[ ! wire4 ,! wire at once t5ds to move sideways across ! field away f ! cr[d$ side4 ,9 ! figure1 ! wire t5ds to move d[nw>d4 ,illu/ration3 ,,fig4 #bie4--,! magnetic field ab\t a wire c>ry+ a curr5t4 ,illu/ration3 ,,fig4 #bif4--,! magnetic field betwe5 two unlike poles4 ,illu/ration3 ,,fig4 #big4--,! cr[d+ ( ! l9es ( =ce above ! wire1 pu%es x d[nw>d4 ,9 a practical motor1 ! wires ^u ! armature are s connect$ t ^? ^u "o side 7see ,fig4 #bih71 c>ry curr5ts t pass 91 :ile on ! o!r side !y pass out4 ,to repres5t ! direction ( ! curr5t 9 ! wires1 ! foll[+ device is employ$2 a circle ) a cross 7to repres5t ! fea!r 9 ! tail ( an arr[7 indicates a curr5t go+ away f ! obs]v]1 :ile a circle ) a dot at its c5t] 7to repres5t ! tip ( an arr[7 indicates a curr5t com+ t[>d ! obs]v]4 ,illu/ration3 ,,fig4 #bih4--,! cr[d+ ( ! l9es ( =ce causes ! armature to revolve 9 a clockwise direction4 ,9 ,fig4 #bih ! nor? pole is at ! left & ! s\? pole at ! "r4 ,! field ( ! magnets !re=e passes f left to "r z indicat$ 9 ! figure4 ,n[ 9 ! armature ! curr5ts 9 ! wires on ! left half ( ! armature are com+ t[>d ! obs]v] :ile ^? on ! "r move away4 ,apply+ ! "r-h& rule1 ! magnetic l9es w cr[d "u ! wires on ! left side ( ! armature :ile !y w cr[d ov] ! wires on ! "r side4 ,?is w cause a rotation up on ! left side & d[n on ! "r1 or 9 a clockwise direction4 ,illu/ration3 ,,fig4 #bii4--,view ( a "o-half horse-p[] motor4 ,if ! curr5t 9 ! armature is rev]s$ 79 on ! left & out on ! "r71 ! l9es ( =ce w cr[d ! armature ar\nd 9 ! opposite direction or c\nt] clockwise4 ,! rotation ( ! armature w also be rev]s$ if1 :ile ! curr5t 9 ! armature is un*ang$ 9 direction1 ! poles ( ! magnet are *ang$ ?us rev]s+ ! magnetic field4 ,! motorman ( a /reet c> rev]ses ! motion ( 8 c> by rev]s+ ! direction ( ! curr5t 9 ! armature ( ! motor4 ,illu/ration3 ,,fig4 #cjj4--,! frame & electromagnet 7at left71 front bracket & bru% hold] 7at "r7 ( ! motor %[n 9 ,fig4 #bii4 ,illu/ration3 ,,fig4 #cja4--,! armature ( a motor4 #cjf4 ,practical motors h _m coils ^u ! armature ) a correspond+ numb] ( segm5ts ^u ! commutator4 ,a l>ge numb] ( coils & commutator segm5ts enables "s "o ( ! coils to ex]t its greate/ effici5cy at ea* in/ant1 h5ce a /eady =ce is provid$ = turn+ ! armature :i* causes x to run smoo?ly4 ,fig4 #bii repres5ts a #a_/b horse-p[] motor ready = use :ile ,fig4 #cjj %[s ! frame & poles & ! front bracket & bru% hold]1 & ,fig4 #cja repres5ts ! armature4 ,important ,topics #a4 ,! dynamo1 f\r ess5tial p>ts1 action 7a7 = alt]nat+ curr5ts1 7b7 = direct curr5ts4 #b4 ,! electric motor3 7a7 ess5tial p>ts1 7b7 action4 ,ex]cises #a4 ,:y is an alt]nat+ curr5t produc$ 9 ! armature ( a dynamo8 #b4 ,h[ is ?is curr5t produc$8 ,give c>eful explanations4 #c4 ,:at is ! result ( ,l5z's law z appli$ to ! dynamo8 #d4 ,apply ! fir/ two laws ( electromagnetic induction to ! dynamo4 #e4 ,:at is ! p[] ( a dynamo if x produces #dj amp]es ( curr5t at #aaj volts8 #f4 ,h[ mu* p[] mu/ be appli$ to ?is dynamo if its effici5cy is #ij p] c5t48 #g4 ,a motor takes #aj amp]es ( curr5t at #bbj volts2 :at is ! p[] ( ! curr5t 9 watts8 ,if ?is motor has an effici5cy ( #ie p] c5t41 h[ _m horse-p[] ( me*anical en]gy c x develop8 #h4 ,expla9 :y rev]s+ ! curr5t 9 ! armature ( a motor rev]ses ! direction ( rotation4 #i4 ,f9d ! co/ ( runn+ a wa%+ ma*9e us+ a #a_/b-;horsep[] motor #b h\rs if ! co/ ( ! electricity is #aj c5ts a kil[att h\r4 #aj4 ,a #a_/h-;horse-p[] motor is us$ to run a sew+ ma*9e4 ,if us$ = #c h\rs :at w be ! co/ at #aa c5ts a kil[att h\r8 7#c7 ,,! ,,induction ,,coil ,,& ,,! ,,trans=m] #cjg4 ,! ,induction ,coil4--,practically all electric curr5ts are produc$ ei!r by voltaic cells or by dynamos4 ,x is frequ5tly f\nd1 h[ev]1 t x is desirable to *ange ! ,e4,m4,f4 ( ! curr5t us$1 ei!r = purposes ( effectiv5ess1 conv5i5ce1 or economy4 ,! induction coil & ! trans=m]1 devices = *ang+ ! ,e4,m4,f4 ( electric curr5ts1 are !re=e 9 common use4 ,! induction coil 7see ,fig4 #cjb7 consi/s ( a prim>y coil ( co>se wire ,p 7,fig4 #cjc7 w\nd ^u a core ( s(t iron wire1 & a second>y coil1 ,s1 ( sev]al ?\s& turns ( f9e wire4 ,9 circuit ) ! prim>y coil is a batt]y1 ,b1 & a curr5t int]rupt]1 ,k1 :i* works l ! int]rupt] ^u an electric bell4 ,! ends ( ! second>y coil are br\ght to b9d+ po/s or sp>k po9ts z at ,d4 ,illu/ration3 ,,fig4 #cjb4--;,an induction coil4 ,! curr5t f ! batt]y fl[s ?r\gh ! prim>y coil magnetiz+ ! iron core4 ,! magnetism 9 ! core attracts ! s(t-iron end ( ! int]rupt]1 draw+ ! latt] ov] & break+ ! circuit at ! screw contact1 ,k4 ,?is abruptly /ops ! curr5t & at once ! core loses its magnetism4 ,! spr+ support ( ! int]rupt] n[ draws ! latt] back to ! contact1 ,t1 aga9 complet+ ! circuit4 ,! :ole op]ation is repeat$1 ! int]rupt] vibrat+ rapidly cont9ually op5+ & clos+ ! circuit4 ,illu/ration3 ,,fig4 #cjc4--;,diagram %[+ ! p>ts ( an induction coil4 #cjh4 ,! ,production ( ,induc$ ,curr5ts 9 ! ,second>y ,coil4--,:5 ! curr5t fl[s ?r\gh ! prim>y x sets up a magnetic field 9 ! core4 ,:5 ! curr5t is int]rupt$1 ! field disappe>s4 ,! increase & decrease 9 ! field ( ! core induces an ,e4,m4,f4 9 ! second>y coil1 9 accordance ) ! fir/ law ( electromagnetic induction4 ,! ,e4,m4,f4 produc$ dep5ds ^u 7a7 ! numb] ( turns 9 ! second>y1 7b7 ! /r5g? ( ! magnetic field & 7c7 ! rate ( *ange ( ! field4 ,! rate ( *ange 9 ! field is m rapid at ! break ?an at ! make4 ,:5 ! circuit is clos$ x takes p]haps #a_/aj ( a second = ! curr5t to build up to its full /r5g? :ile at a break ! curr5t /ops 9 p]haps #j4jjjja ( a second1 s t ! induc$ ,e4,m4,f4 is p]haps #aj1jjj times z great at break z at make4 ,to increase ! sudd5ness ( ! make & break1 a cond5s] is (t5 connect$ 9 ! prim>y circuit1 9 p>allel1 ) ! int]rupt]4 7,see ,fig4 #cjc1 ,c47 ,?is cond5s] provides a place to hold ! ru% ( curr5t at ! in/ant t ! int]rupt] breaks ! circuit4 ,?is /or$ up *>ge re9=ces ! curr5t at ! make produc+ a mu* m sudd5 *ange 9 ! magnetic field ) a correspond+ increase 9 ! ,e4,m4,f4 ,! induc$ curr5ts f induction coils are sometimes call$ f>adic curr5ts 9 honor ( ,f>aday :o discov]$ electromagnetic induction4 ,!y are us$ to op]ate sp>k+ devices ^u gas & gasol9e eng9es & 9 _m devices & exp]im5ts 9 :i* high-t5sion electricity is employ$4 ,illu/ration3 ,,fig4 #cjd4--,! trans=m] has a clos$ core2 ! induction coil1 an op5 core4 ,illu/ration3 ,,fig4 #cje4--,! lam9at$ iron core ( a trans=m]4 ,illu/ration3 ,,fig4 #cjf4--;,cross-section ( ! trans=m] %[n 9 ,fig4 #cje %[+ ! magnetic field ar\nd ! prim>y & second>y coils4 #cji4 ,! ,trans=m]4--,?is is l ! induction coil 9 t x uses a prim>y & a second>y coil1 & an iron core to c>ry ! magnetic field4 7,see ,fig4 #cjd47 ,!y diff] 9 t ! trans=m] has a clos$ core or "o =m+ a cont9u\s iron circuit1 :ile ! induction coil has an op5 core1 or "o 9 :i* ! magnetic field mu/ travel 9 air f ! nor? to ! s\? poles ( ! core4 ,! trans=m] mu/ always be us$ ) an alt]nat+ curr5t :ile ! induction coil may use ei!r a direct or an alt]nat+ curr5t4 ,fur!r1 ! induction coil always produces a high] ,e4,m4,f4 :ile ! trans=m] may produce an ,e4,m4,f4 9 its second>y coil t is ei!r high] or l[] ?an ! "o 9 ! prim>y4 ,! =m] is call$ /ep-up :ile ! latt] is a /ep-d[n trans=m]4 ,! alt]nat+ curr5t 9 ! prim>y coil ( ! trans=m] produces an alt]nat+ magnetic flux 9 ! iron core4 ,?is iron core is lam9at$ 7see ,fig4 #cje7 to prev5t ! heat+ t w\ld result if a solid core 7 us$4 ,! alt]nat+ magnetic flux induces 9 ! second>y coil an ,e4,m4,f4 9 accordance ) ! foll[+ rule4 ,! ratio ( ! numb] ( turns 9 ! prim>y to ! numb] ( ! turns 9 ! second>y coil equals ! ratio ( ! electromotive =ces 9 ^! respective coils4 ,if ! second>y coil has #h turns :ile ! prim>y has #d1 ! ,e4,m4,f4 ( ! second>y w be j twice t ( ! prim>y4 ,or1 if 9 ! prim>y coil ( ! trans=m] ,fig4 #cjf is an ,e4,m4,f4 ( #aaj volts1 9 ! second>y w be f\nd an ,e4,m4,f4 ( #bbj volts4 ,illu/ration3 ,,fig4 #cjg4--;,a comm]cial trans=m]4 #caj4 ,uses ( ,trans=m]s4--,9 electric light+ sy/ems1 dynamos (t5 produce alt]nat+ curr5ts at #ajjj to #ab1jjj volts pressure4 ,x is v dang]\s to admit curr5ts at ?is pressure into dwell+s & bus9ess h\ses1 s t trans=m]s are in/all$ j outside ( build+s to /ep-d[n ! high voltage curr5ts to #aaj or #bbj volts4 ,! light+ curr5t t ent]s a h\se does n come directly f a dynamo4 ,x is an induc$ curr5t produc$ by a trans=m] plac$ ne> ! h\se4 7,see ,fig4 #cjg47 ,9 a p]fect trans=m] ! effici5cy w\ld be #ajj p] c5t4 ,?is signifies t ! en]gy t is s5t into ! prim>y coil ( ! trans=m] exactly equals ! en]gy 9 ! second>y coil4 ,! be/ trans=m]s actually %[ effici5cies bett] ?an #ig p] c5t4 ,! lo/ en]gy appe>s z heat 9 ! trans=m]4 ,! transf] ( great p[] 9 a l>ge trans=m] f "o circuit to ano!r circuit entirely sep>ate & di/9ct1 )\t any motion or noise & almo/ )\t loss1 is "o ( ! mo/ wond]ful ph5om5a "u ! control ( man4 #caa4 ,! m]cury arc rectifi] is a device = *ang+ an alt]nat+ curr5t into a direct curr5t4 ,x is frequ5tly us$ = *>g+ /orage batt]ies :]e only alt]nat+ curr5t is suppli$ by ! electric p[] company4 ,x consi/s ( an exhau/$ bulb conta9+ two c>bon or graphite electrodes m>k$ ,g 9 ,fig4 #cjh & a m]cury electrode m>k$ ,m4 ,x is f\nd t curr5t w pass ?r\gh su* a bulb only f ! graphite to ! m]cury b n 9 ! rev]se direction4 ,9 op]at+ ! device1 ! second>y t]m9als ( an alt]nat+ curr5t trans=m] ,t are connect$ to ! graphite t]m9als ( ! rectifi]4 ,a wire connect$ to ! c5t] ( ! second>y ( ! trans=m] at ,c is atta*$ to ! negative t]m9al ( ! /orage batt]y ,,sb4 ,! positive t]m9al ( ! batt]y is connect$ to ! m]cury electrode ( ! rectifi] tube ?r\gh a reactance or *oke coil ,r4 ,?is coil s]ves to su/a9 ! arc betwe5 ! alt]nations4 ,sw is a />t+ swit*1 us$ only 9 /rik+ ! arc4 ,x is op5$ imm$iately aft] ! tube beg9s to gl[4 ,illu/ration3 ,,fig4 #cjh4--;,diagram ( a m]cury arc rectifi]4 ,important ,topics ,trans=m]1 induction coil1 m]cury arc rectifi]1 con/ruction1 action2 uses ( ea*4 ,ex]cises #a4 ,does ! sp>k ( an induction coil occur at make or at break8 ,:y8 #b4 ,:at mu/ be ! relative numb] ( turns ^u ! prim>y & second>y coils ( a trans=m] if x receives curr5t at #bbj volts & deliv]s curr5t at #aaj8 ,also %[ by diagram4 #c4 ,w\ld ! trans=m] "w ^u a direct curr5t8 ,:y8 #d4 ,expla9 :y ! int]rupt] is a necess>y "p ( ! induction coil & n ( ! trans=m]4 #e4 ,if a build+ us$ eighty #aaj-volt inc&esc5t lamps1 :at w\ld be necess>y to light !m if !y 7 jo9$ 9 s]ies8 ,:y w\ld ?is n be practical8 #f4 ,if a #af-;c&le-p[] lamp requires #j4e amp]e ^u a #aaj-volt circuit :at curr5t & voltage w be ne$$ to op]ate #ab su* lamps 9 p>allel8 #g4 ,:at w x co/ to run ^! lamps #d h\rs a night = #cj days at #aj c5ts p] kil[att h\r8 #h4 ,if a m]cury arc rectifi] uses #e amp]es ( curr5t at #aaj volts alt]nat+ curr5t to produce #e amp]es ( direct curr5t at #gj volts1 :at is ! effici5cy ( ! rectifi]8 #i4 ,compute ! heat produc$ 9 a #dj watt tung/5 lamp 9 #a m9ute4 #aj4 ,compute ! heat produc$ 9 a #fj watt c>bon inc&esc5t lamp 9 #a h\r4 7#d7 ,,! ,,telephone #cab4 ,! ,electric ,telephone4--,?is is an in/rum5t = reproduc+ ! human voice at a di/ance by an electric curr5t4 ,! mod]n electric telephone consi/s ( at lea/ f\r di/9ct p>ts 7see ,fig4 #cab72 viz41 a transmitt]1 an induction coil1 an electric batt]y1 & a receiv]4 ,! fir/ ?ree ( ^! are conc]n$ 9 s5d+1 or transmitt+ ov] ! connect+ wires a fluctuat+ electric curr5t1 :i* has be5 modifi$ by ! waves ( a human voice4 ,! receiv]1 is affect$ by ! fluctuat+ curr5t & reproduces ! voice4 ,x w be consid]$ fir/1 9 our /udy4 #cac4 ,! telephone receiv] 0 inv5t$ 9 #ahgf by ,alex&] ,graham ,bell4 ,x consi/s ( a p]man5t /eel magnet1 ,u %ap$1 ) a coil ( f9e insulat$ copp] wire ab\t ea* pole4 7,see ,fig4 #caj47 ,a disc ( ?9 %eet iron is support$ s t its c5t] does n q t\* ! poles ( ! magnet4 ,a h>d rubb] cap or e> piece ) an op5+ at its c5t] is screw$ on s z to hold ! iron disc firmly 9 place4 ,illu/ration3 ,,fig4 #cji4--,! simple/ telephone sy/em4 ,x consi/s ( two telephone receiv]s connect$ 9 s]ies on a circuit4 ,x w "w1 b n satisfactorily4 ,! action ( ! receiv] may be und]/ood f ! foll[+ explanation3 ,! electric curr5t s5t to ! receiv]1 comes f ! second>y coil ( ! induction coil2 x is an alt]nat+ curr5t1 fluctuat+ back & =? j 9 "t ) ! waves ( ! voice affect+ x at ! transmitt]4 ,?is alt]nat+ curr5t fl[s ar\nd ! coils on ! poles ( ! p]man5t magnet4 ,:5 ?is curr5t fl[s 9 "o direction1 its magnetic field assi/s ! field ( ! p]man5t magnet1 /r5g!n+ x4 ,?is /rong] magnetic field draws ! ?9 iron disc 9 front ( ! poles ( ! magnet a little clos] to !m4 ,:5 ! curr5t 9 ! coils fl[s ! o!r way1 its magnetic field weak5s ! field ( ! /eel magnet1 & ! disc is drawn back by ! =ce ( its own ela/icity4 ,?us ! disc ( ! receiv] vibrates ) ! alt]nations ( ! curr5t1 & reproduces ! same s\nds t 7 spok5 into ! transmitt]4 ,illu/ration3 ,,fig4 #caj4--;,a telephone receiv]4 ,?is receiv] has a p]man5t horse%oe magnet ) a coil ab\t ea* pole4 #cad4 ,! ,telephone ,transmitt]4--,! telephone receiv] j describ$ has great s5sitiv5ess 9 reproduc+ s\nd1 b x is n satisfactory z a transmitt] or s5d+ app>atus4 ,! transmitt] commonly us$ is repres5t$ 9 cross-section 9 ,fig4 #caa4 ,9 ?is figure1 back ( ! m\?piece1 is a ?9 c>bon disc1 ,d4 ,back ( ?is disc is a circul> comp>tm5t conta9+ granul> c>bon1 g4 ,! wires ( ! circuit are connect$ to ! c>bon disc & to ! back ( ! case conta9+ granul> c>bon4 ,! circuit ?r\gh ! transmitt] also includes a voltaic or /orage cell & ! prim>y coil ( an induction coil4 7,see ,fig4 #cab47 ,illu/ration3 ,,fig4 #caa4--;,a telephone transmitt]4 ,illu/ration3 ,,fig4 #cab4--,telephone in/rum5ts at "o end ( a talk+ circuit4 #cae4 ,! action ( ! transmitt] is expla9$ z foll[s3 ,:5 ! s\nd waves ( ! voice /rike ^u ! c>bon disc1 ! latt] vibrates1 alt]nately increas+ & decreas+ ! pressure ^u ! granul> c>bon4 ,:5 ! pressure increases1 ! electrical resi/ance ( ! granul> c>bon is less5$1 & :5 ! pressure ^u x is decreas$1 its resi/ance increases4 ,?is *ang+ resi/ance causes fluctuations 9 ! electric curr5t t correspond exactly ) ! s\nd waves ( ! voice affect+ x4 #caf4 ,a complete telephone sy/em op]at+ ) a local batt]y is %[n 9 ,fig4 #cab4 ,a p]son speak+ into ! transmitt] causes a fluctuation 9 ! electric curr5t 9 ! transmitt] z describ$ 9 ,art4 #cae4 ,?is fluctuat+ curr5t passes ?r\gh ! prim>y coil ( ! induction coil ,ic4 ,?is fluctuat+ curr5t produces a fluctuat+ magnetic field 9 its core4 ,?is fluctuat+ field induces an alt]nat+ curr5t 9 ! second>y coil :i* alt]nates j z ! prim>y curr5t fluctuates1 b ) a mu* high] ,e4,m4,f4 ?an ! latt]4 ,! alt]nat+ curr5t passes to ! receiv] :i* reproduces ! spee* z describ$ 9 ,art4 #cac4 ,! l9e circuit includes ! second>y ( ! induction coil1 ! receiv+ in/rum5t & ! receiv] ( ! s5d+ in/rum5t s t ! voice is reproduc$ 9 bo? receiv]s4 ,an electric bell is plac$ at ea* /ation to call ! att5tion ( p>ties want$4 ,! movem5t ( ! receiv] hook :5 ! receiv] is lift$1 disconnects ! bell & closes ! talk+ circuit4 ,! latt] is op5$ & ! bell connect$ :5 ! receiv] is hung up aga94 ,illu/ration3 ,,fig4 #cac4--;,diagram ( a telephone sy/em z us$ 9 a l>ge ex*ange4 ,9 cities & t[ns1 ! telephone sy/em 9 use diff]s f ! "o describ$ 9 usually hav+ "o l>ge batt]y plac$ 9 ! c5tral ex*ange1 in/ead ( dry cells at ea* in/rum5t4 7,see ,fig4 #cac47 ,also ! op]ator at c5tral is call$ by simply tak+ ! receiv] f ! hook in/ead ( be+ rung up by ! subscrib]4 ,! op]ations ( ! transmitt]1 induction coil & receiv]1 h[ev]1 are ! same 9 all telephones4 ,important ,topics #a4 ,receiv]3 p>ts1 action4 #b4 ,transmitt]3 p>ts1 action4 #c4 ,induction coil1 bell1 l9e wires1 etc4 #d4 ,action ( ! :ole device4 ,ex]cises #a4 ,/ate ?ree important electrical laws or pr9ciples t are employ$ 9 ! op]ation ( ! telephone4 ,:at is ! application ( ea*8 #b4 ,connect ! b9d+ po/s ( a telephone receiv] ) a s5sitive galvanomet] & press on ! diaphragm ( ! receiv]2 a deflection ( ! galvanomet] w be notic$4 ,release ! diaphragm & a reflection 9 ! opposite direction is se54 ,expla94 #c4 ,is ! curr5t pass+ ?r\gh ! transmitt] ! "o go+ to ! receiv] ( ! in/rum5t8 ,expla94 #d4 ,does ! receiv] at ! telephone us$ by a p]son repeat ! spee* ( ! p]son8 ,expla94 #e4 ,h[ _m #j4e amp]e lamps c be us$ ) a #f amp]e fuse8 #f4 ,:y is x necess>y to h a rheo/at connect$ 9 s]ies ) a /]eopticon or mov+ picture ma*9e :ile a rheo/at is n us$ ) arc lights out doors8 #g4 ,h[ _m c&le p[] %\ld a #fj watt c>bon inc&esc5t lamp give1 if its effici5cy is #c4d watts p] c&le p[]8 #h4 ,?ree inc&esc5t lamps hav+ resi/ances ( #ajj1 #aej1 & #bdj ohms1 respectively1 are connect$ 9 p>allel4 ,:at is _! comb9$ resi/ance8 ,review ,outl9e3 ,induc$ ,curr5ts ,induc$ curr5ts2 #c laws1 illu/rations4 ,con/ruction1 action1 & uses (--magneto1 dynamo1 induction coil1 trans=m]1 motor1 telephone4 ,m]cury arc rectifi]4 ,t]ms--prim>y1 second>y1 = coils & curr5ts1 armature1 commutator1 slip r+1 bru%1 rectifi]1 op5 core1 s]ies1 %unt1 & comp\nd connections = dynamos4 ,,*apt] ,,xv ,,s\nd 7#a7 ,,s\nd ,,& ,,wave ,,motion #cag4 ,:at is a ,s\nd8--,?is "q has two answ]s1 :i* may be illu/rat$ z foll[s3 ,suppose t an al>m clock is set s t x w /rike 9 "o week & t x is plac$ ^u a b>r5 rock 9 ! ,pacific ,ocean by sailors :o imm$iately sail away4 ,if :5 ! tapp] /rikes ! bell at ! end ( ! week no e> is )9 a hundr$ miles1 is any s\nd produc$8 ,! two view-po9ts are n[ made evid5t1 = "s w answ] no o!rs yes4 ,^? answ]+ no hold t s\nd is a s5sation :i* w\ld n be produc$ if no e> 7 at h& to be affect$4 ,^? answ]+ yes und]/&1 by ! t]m s\nd1 a mode ( motion capable ( affect+ ! auditory n]ves1 & t s\nd exi/s :]ev] su* motions are pres5t4 ,?is latt] po9t ( view is call$ ! physical & is ! "o we are to use 9 ?is /udy4 ,illu/ration3 ,,fig4 #cad4--,! tun+ =k is vibrat+4 #cah4 ,s\rce ( ,s\nd4--,if we trace any s\nd to its s\rce1 x w be f\nd to orig9ate 9 a body 9 rapid motion usually 9 :at is call$ a /ate ( vibration4 ,to illu/rate1 take a tun+ =k1 /rike x to set x 9 vibration & place its /em firmly aga9/ a ?9 piece ( wood2 ! s\nd w be /r5g!n$ mat]ially by ! vibration ( ! wood4 ,if n[ ! vibrat+ =k is plac$ ) ! tips ( ! prongs 9 wat]1 ! vibration is pla9ly %[n by ! spatt]+ ( ! wat] 7,fig4 #cad74 ,:5 "o speaks1 ! vibrat+ body is 9 ! l>ynx at ! top ( ! w9dpipe4 ,its vibration may be pla9ly felt by ! h& plac$ ^u ! ?roat :ile speak+4 #cai4 ,s\nd ,m$ia4--,usually s\nds rea* ! e> ?r\gh ! air4 ,! air is !n said to be a m$ium = s\nd4 ,o!r sub/ances may s]ve z a s\nd m$ium1 = if ! head is "u wat] & two /ones1 also "u wat]1 are /ruck toge!r a %>p s\nd is he>d4 ,also if "o end ( a wood5 rod is held at ! e> & ! o!r end ( ! rod is scrat*$ by a p91 ! s\nd is m pla9ly p]ceiv$ ?r\gh ! wood ?an ?r\gh ! air4 ,?9k ( "s illu/ration f y\r own exp]i5ce ( a solid act+ z m$ium = s\nd4 ,if an electric bell is plac$ 9 a bell j> atta*$ to an air pump1 z 9 ,fig4 #cae1 on exhau/+ ! air ! l\dness ( ! s\nd is f\nd to dim9i%1 indicat+ t 9 a p]fect vacuum no s\nd w\ld be transmitt$4 ,?is effect ( a vacuum ^u ! transmission ( s\nd is v diff]5t f its effect ^u radiation ( heat & light4 ,bo? heat & light are kn[n to pass ?r\gh a vacuum s9ce bo? come to ! e>? f ! sun ?r\gh space t s f> z we "k conta9s no air or o!r matt]4 ,s\nd diff]s f ?is 9 t x is always transmitt$ by "s mat]ial body & _c exi/ 9 a vacuum4 ,illu/ration3 ,,fig4 #cae4--,s\nd does n travel 9 a vacuum4 #cbj4 ,spe$ ( ,s\nd4--,ev]yone has notic$ t x takes "t = s\nd to travel f "o place to ano!r4 ,if we see a gun fir$ at a di/ance1 ! report is he>d a few seconds aft] ! smoke or fla% is se54 ,! "t elaps+ betwe5 a fla% ( lightn+ & ! ?und] %[s t s\nd takes "t to move f "o place to ano!r4 ,c>eful exp]im5ts to det]m9e ! spe$ ( s\nd h be5 made4 ,"o me?od measures accurately ! "t requir$ = ! s\nd ( a gun to pass betwe5 two /ations sev]al miles ap>t4 ,a gun or cannon is plac$ at ea* /ation4 ,^! are fir$ alt]nately1 fir/ ! "o at "o /ation & !n ! "o at ! o!r s z to avoid an error 9 computation due to ! motion ( w9d4 ,?is mode ( det]m9+ ! spe$ ( s\nd is n accurate4 ,o!r me?ods1 m ref9$ ?an ! "o j describ$ h giv5 accurate values = ! spe$ ( s\nd4 ,! results ( a numb] ( exp]im5ts %[ t1 at ! freez+ temp]ature1 #j;,c41 ! spe$ ( s\nd 9 air is #ccb met]s or #ajij ft4 a second4 ,! spe$ ( s\nd 9 air is affect$ by ! temp]ature1 increas+ #b ft4 or #j4f met] p] second = ea* degree t ! temp]ature rises above #j;,c4 ,! spe$ decreases ! same am\nt = ea* degree ,c4 t ! air is cool$ bel[ ! freez+ po9t4 ,! spe$ ( s\nd 9 v>i\s sub/ances has be5 c>efully det]m9$4 ,x is great] 9 mo/ ( !m ?an 9 air4 ,9 wat] ! spe$ is ab\t #adjj met]s a second2 9 wood1 :ile its spe$ v>ies ) diff]5t k9ds1 x av]ages ab\t #djjj met]s a second2 9 brass ! spe$ is ab\t #cejj met]s2 :ile 9 iron x is ab\t #eajj met]s a second4 #cba4 ,! ,nature ( ,s\nd4--,we h obs]v$ t s\nd orig9ates at a vibrat+ body1 t x requires a m$ium 9 ord] to be transmitt$ f "o place to ano!r1 & t x travels at a def9ite spe$ 9 a giv5 sub/ance4 ,no?+ has be5 said1 h[ev]1 ( ! mode ( transmission1 or ( ! nature ( s\nd4 ,s\nds cont9ue to come f an al>m clock ev5 ?\gh x is plac$ "u a bell j>4 ,x is c]ta9 t no?+ mat]ial c pass ?r\gh ! glass ( ! j>4 ,if1 h[ev]1 we consid] t s\nd is transmitt$ by waves ?r\gh sub/ances ! :ole matt] c be giv5 a simple explanation4 ,9 ord] to bett] und]/& ! nature ( s\nd a /udy ( waves & wave motion w be tak5 up 9 ! next section4 ,important ,topics ,s\nd3 two def9itions1 s\rce1 m$ium1 spe$1 nature4 ,ex]cises #a4 ,give two illu/rations f outside ! laboratory ( ! fact t s\nd is transmitt$ by o!r mat]ials ?an air4 #b4 ,"n ! vibrat+ "p t is ! s\rce ( ! s\nd 9 ?ree diff]5t musical in/rum5ts4 #c4 ,is s\nd transmitt$ m /rongly 9 solids1 liquids or gases8 ,h[ d y expla9 ?is8 #d4 ,h[ f> away is a /eamboat if ! s\nd ( its :i/le is he>d #aj seconds aft] ! /eam is se51 ! temp]ature be+ #bj;,c48 ,compute 9 feet & 9 met]s4 #e4 ,h[ _m miles away is lightn+ if ! ?und] is he>d #ab seconds aft] ! fla% 9 se51 ! temp]ature be+ #be;,c48 #f4 ,f\r seconds aft] a fla% ( lightn+ is se5 ! ?und] clap is he>d4 ,! temp]ature is #ij;,f4 ,h[ f> away 0 ! dis*>ge8 #g4 ,! report ( a gun is he>d #c seconds aft] ! puff ( smoke is se54 ,h[ f> away is ! gun if ! temp]ature is #bj;,c48 #h4 ,an explosion takes place #aj miles away4 ,h[ long w x take ! s\nd to rea* y1 ! temp]ature be+ #hj;,f84 ,h[ long at #j;,f48 #i4 ,h[ long aft] a :i/le is s\nd$ w x be he>d if ! di/ance away is #a_/d mile1 ! temp]ature be+ #ij;,f48 #aj4 ,! report ( an explosion ( dynamite is he>d #b m9utes aft] ! puff ( smoke is se54 ,h[ f> away is ! explosion ! temp]ature be+ #gg;,f48 7#b7 ,,waves,n ,,& ,,wave ,,motion ,n ,a wave is a di/urbance 9 a sub/ance or m$ium t is transmitt$ ?r\gh x4 #cbb4 ,visible ,waves4--,x is be/ to beg9 ! /udy ( wave motion by consid]+ "s waves :i* are famili> to mo/ p]sons4 ,take = example ! waves t move ov] ! surface ( wat] 7,fig4 #caf74 ,^! h an onw>d motion1 yet bo>ds or *ips ^u ! surface simply rise & fall z ! waves pass !m4 ,!y are n c>ri$ onw>d by ! waves4 ,! wat] surface simply rises & falls z ! waves pass by4 ,consid] also ! waves t may be se5 to move across a field ( tall grass or gra94 ,su* waves are produc$ by ! b5d+ & ris+ ( ! /alks z ! w9d passes ov] !m4 ,aga91 waves may be produc$ 9 a rope fa/5$ at "o end1 by sudd5ly mov+ ! o!r end up & d[n4 ,^! waves move to ! end ( ! rope :]e !y are reflect$ & return4 ,! ?ree types ( waves j m5tion$ are illu/rations ( transv]se waves1 ! ideal case be+ t 9 :i* ! p>ticles move at "r angles to ! pa? or c\rse ( ! wave4 ,su* waves are !re=e call$ transv]se waves4 ,illu/ration3 ,,fig4 #caf4--,wat] waves4 #cbc4 ,longitud9al waves4--,ano!r k9d ( wave is f\nd 9 bodies t are ela/ic & compressible & h in]tia1 su* z gases & coil$ wire spr+s4 ,su* waves may be /udi$ by consid]+ a wire spr+ z ! m$ium ?r\gh :i* ! waves pass4 7,see ,fig4 #cah47 ,illu/ration3 ,,fig4 #cag4--,! compression wave travels ?r\gh ! spr+4 ,if ! end ( ! wire spr+ %[n 9 ,fig4 #cag is /ruck ! fir/ few turns ( ! spr+ w be compress$4 ,s9ce ! spr+ possesses ela/icity1 ! turns w move =w>d a little & compress ^? ahead1 ^! w press ! next 9 turn & s on4 ,?us a compression wave w move to ! end ( ! spr+1 :]e x w be reflect$ & return4 ,consid] ! turns ( ! spr+ z !y move t[>d ! end4 ,on acc\nt ( _! in]tia !y w cont9ue mov+ until !y h sep>at$ f ea* o!r m ?an at fir/1 be=e return+ to _! usual position4 ,?is condition ( a great] sep>ation ( ! turns ( ! spr+ ?an usual is call$ a r>efaction4 ,x moves along ! spr+ foll[+ ! wave ( compression4 ,! cond5sation & r>efaction are consid]$ z toge!r =m+ a complete wave4 ,s9ce ! turns ( wire move back & =? 9 a direction p>allel to t 9 :i* ! wave is travel+1 ^! waves are call$ longitud9al4 ,illu/ration3 ,,fig4 #cah4--,longitud9al waves 7#a7 9 a spr+1 7#b7 9 air1 & 7#c7 graphic repres5tation %[+ wave l5g?1 cond5sations1 & r>efactions4 #cbd4 ,! transmission ( a s\nd by ! air may be und]/ood by comp>+ x ) ! process by :i* a wave is transmitt$ by a wire spr+4 ,consid] a light spr+ 7,fig4 #cah1 #a7 atta*$ at ! end ( a vibrat+ tun+ =k1 ,k1 & also to a diaphragm1 ,d4 ,ea* vibration ( ! =k w fir/ compress & !n sep>ate ! coils ( ! spr+4 ,^! impulses w be transmitt$ by ! spr+ z describ$ 9 ,art4 #cae1 & cause ! diaphragm to vibrate at ! same rate z ! tun+ =k4 ,! diaphragm w !n give out a s\nd simil> to t ( ! tun+ =k4 ,suppose t ! spr+ is replac$ by air1 & ! diaphragm1 by ! e> ( a p]son1 ,e1 7,fig4 #cah1 #b47 :5 ! prong ( ! =k moves t[>d ! e> x />ts a compression & :5 x moves back a r>efaction4 ,! =k cont9ues vibrat+ & ^! impulses move onw>d l ^? 9 ! spr+ at a spe$ ( ab\t #aabj ft4 9 a second4 ,!y /rike ! diaphragm ( ! e> caus+ x to move back & =? or to vibrate at ! same rate z ! tun+ =k1 j z 9 ! case ( ! diaphragm atta*$ to ! spr+4 #cbe4 ,graphic ,repres5tation ( ,s\nd waves4--,x is frequ5tly desirable to repres5t s\nd waves graphically4 ,! usual me?od is to use a curve l t 9 7,fig4 #cah1 #c74 ,?is curve is consid]$ z repres5t+ a tra9 ( waves mov+ 9 ! same direction z ^? 9 ,fig4 #cah #a & #b1 & also hav+ ! same l5g?4 ,! "p ( ! wave ,a-,b repres5ts a cond5sation ( ! s\nd wave & ! "p ,b-,c repres5ts a r>efaction4 ,a complete wave consi/+ ( a cond5sation & a r>efaction is repres5t$ by t portion ( ! curve ,a-,c4 ,! portion ( ! curve ,b-,d also repres5ts a full wave l5g? z ! latt] is def9$ z ! di/ance betwe5 two correspond+ p>ts ( ! adjac5t waves4 ,! curve1 ,fig4 7#cah1 #c7 repres5ts n only ! wave l5g?1 b also ! height ( ! wave or ! am\nt ( movem5t ( ! p>ticles along ! wave4 ,?is is call$ ! amplitude & is indicat$ by ! di/ance ,a-b4 ,s9ce ! l\dness or int5sity ( a s\nd is f\nd to dep5d ^u ! am\nt ( movem5t ( ! p>ticles along ! wave1 ! amplitude ( ! curve is us$ to indicate ! l\dness ( ! s\nd repres5t$4 ,all ( ! *>act]i/ics ( a s\nd wave may be graphically repres5t$ by curves4 ,su* curves w be us$ frequ5tly z an aid 9 expla9+ ! ph5om5a ( wave motion bo? 9 s\nd & 9 light4 #cbf4 ,reflections ( ,s\nd4--,x is f\nd t a wave mov+ along a wire spr+ is reflect$ :5 x rea*es ! end & returns along ! spr+4 ,simil>ly a s\nd wave 9 air is reflect$ ^u /rik+ ! surface ( a body4 ,if ! wave /rikes p]p5dicul>ly x returns along ! l9e f :i* x comes1 if1 h[ev]1 x /rikes at "s o!r angle x does n return along ! same l9e1 b z 9 o!r cases ( reflect$ motion1 ! direction ( ! reflect$ wave is describ$ by ! ,law ( ,reflect$ ,motion z foll[s3 ,! angle ( reflection is always equal to ! angle ( incid5ce4 ,?is law is illu/rat$ 9 ,fig4 #cai4 ,suppose t a s]ies ( waves com+ f a s\rce ( s\nd move f ,h to ,o4 ,aft] /rik+ ! surface ,,ij ! waves are reflect$ & move t[>d ,l along ! l9e ,,ol4 ,let ,,po be p]p5dicul> to ! surface ,,ij at ,o4 ,!n ,,hop is ! angle ( incid5ce & ,,lop is ! angle ( reflection4 ,by ! law ( reflect$ motion ^! angles are equal4 ,9 an ord9>y room :5 a p]son speaks ! s\nd waves reflect$ f ! smoo? walls re9=ce ! s\nd waves mov+ directly to ! he>]s4 ,x is = ?is reason t x is usually easi] to speak 9 at room ?an 9 ! op5 air4 ,o!r illu/rations ( ! re9=cem5t ( s\nd by reflection are (t5 se54 ,?us an e> trumpet 7,fig4 #cbj71 uses ! pr9ciple ( reflection & conc5tration ( s\nd4 ,s-call$ s\nd+ bo>ds are sometimes plac$ back ( speak]s 9 l>ge halls to reflect s\nd waves to ! audi5ce4 ,illu/ration3 ,,fig4 #cai4--,law ( reflection4 ,illu/ration3 ,,fig4 #cbj4--;,an e> trumpet4 #cbg4 ,e*oes4--,an e*o is ! repetition ( a s\nd caus$ by its reflection f "s di/ant surface su* z t ( a build+1 cliff1 cl\ds1 trees1 etc4 ,! int]val ( "t betwe5 ! production ( a s\nd & ! p]ception ( its e*o is ! "t t ! s\nd takes to travel f its s\rce to ! reflect+ body & back to ! li/5]4 ,exp]im5ts h %[n t ! s5sation ( a s\nd p]si/s ab\t "o-t5? ( a second4 ,s9ce ! velocity ( s\nd at #bj;,c4 is ab\t #aacj ft4 p] second1 dur+ "o-t5? ( a second ! s\nd wave w travel "s #aac ft4 ,if ! reflect+ surface is ab\t #ef ft4 di/ant a %ort s\nd w be foll[$ imm$iately by its e*o z x is he>d "o-t5? ( a second aft] ! orig9al s\nd4 ,! reflect$ s\nd t5ds to /r5g!n ! orig9al "o if ! reflect+ surface is less ?an #ef ft4 away4 ,if ! di/ance ( ! reflect+ surface is mu* m ?an #ef ft4 h[ev]1 ! reflect$ s\nd does n bl5d ) ! orig9al "o b =ms a di/9ct e*o4 ,! e*oes 9 l>ge halls especially ^? ) l>ge smoo? walls may v s]i\sly affect ! cle> p]ception ( ! s\nd4 ,su* rooms are said to h poor ac\/ic prop]ties4 ,furniture1 drap]y1 & c>pets help to dead5 ! e*o because ( diffus$ reflection4 ,! ,mormon ,tab]nacle at ,salt ,lake ,city1 ,utah1 is a f9e example ( a build+ 9 :i* ! reflect+ surfaces ( ! walls & ceil+ are ( su* %ape & mat]ial t its ac\/ic prop]ties are rem>kable1 a p9 dropp$ at "o end be+ pla9ly he>d at ! o!r end ab\t #bjj ft4 away4 ,important ,topics #a4 ,waves3 transv]se1 longitud9al2 wave l5g?1 cond5sation1 r>efaction4 #b4 ,wave motion3 9 coil$ spr+1 9 air1 on wat]4 #c4 ,reflection ( waves3 law1 e*oes4 ,ex]cises #a4 ,a hunt] he>s an e*o 9 #h seconds aft] fir+ 8 gun4 ,h[ f> is ! reflect+ surface if ! temp]ature is #bj;,c48 #b4 ,h[ f> is ! reflect+ surface ( a build+ if ! e*o ( "o's foot/eps returns 9 #a second at #aj;,c48 #c4 ,:y is x easi] to speak or s+ 9 a room ?an out ( doors8 #d4 ,draw a curve t repres5ts wave motion4 ,make x exactly ?ree full wave l5g?s1 & /ate :y y\r curve %[s ?is l5g?4 ,indicate ! p>ts ( ! curve t correspond to a cond5sation & to a r>efaction4 #e4 ,h[ long does x take ! s\nd ( ! p9 drop to rea* a p]son at ! f>!r end ( ! build+ m5tion$ at ! end ( ,art4 #cbg8 #f4 ,an e*o is he>d aft] #f seconds4 ,h[ f> away is ! reflect+ surface1 ! temp]ature be+ #gj;,f48 #g4 ,:y are outdoor b&-/&s g5]ally made ) ! back curv+ ov] ! b&8 #h4 ,a man ne> a =e/ calls to a fri5d4 ,9 #d seconds ! e*o comes back4 ,h[ f> away is he f ! =e/8 #i4 ,w\ld x be possible = u ev] to he> a great explosion ^u ! moon8 ,expla94 #aj4 ,if a sunset gun 0 fir$ exactly at #f3jj ,p4,m4 at a =t1 at :at "t 0 ! report he>d by a man #be miles away1 if ! temp]ature 0 #aj;,c48 7#c7 ,,int5sity ,,& ,,pit* ,,( ,,s\nds ,illu/ration3 ,,fig4 #cba4--;,graphic repres5tations ( 7a7 a noise1 7b7 a musical s\nd4 #cbh4 ,musical ,s\nds & ,noises ,di/+ui%$4--,! "q is sometimes rais$1 :at is ! diff]5ce betwe5 a noise & a musical s\nd8 ,! latt] has be5 f\nd to be produc$ by an ev5 & regul> vibration su* z t ( a tun+ =k or ( a piano /r+4 ,a noise on ! o!r h& is *>act]iz$ by sudd5 or irregul> vibrations su* z ^? produc$ by a wagon bump+ ov] a /ony /reet4 ,^! diff]5ces may be repres5t$ graphically z 9 ,fig4 #cba1 7a7 repres5ts a noise1 7b7 a musical tone4 ,illu/ration3 ,,fig4 #cbb4--;,curve b repres5ts a tone ( great] int5sity4 #cbi4 ,*>act]i/ics ( ,musical ,s\nds4--,musical tones diff] f "o ano!r 9 ?ree ways or are said to h ?ree *>act]i/ics1 viz41 int5sity1 pit*1 & quality4 ,?us two s\nds may diff] only 9 int5sity or l\dness1 t is1 be alike 9 all o!r respects except ?is "o1 z :5 a /r+ ( a piano is /ruck at fir/ g5tly1 & aga9 h>d]4 ,! second s\nd is recogniz$ z be+ l\d]4 ,! diff]5ce is due to ! great] amplitude ( vibration caus$ by m en]gy be+ us$4 ,fig4 #cbb %[s ^! diff]5ces graphically4 ,curve b repres5ts ! tone ( great] int5sity or l\dness1 s9ce its amplitude ( vibration is repres5t$ z be+ great]4 #ccj4 ,conditions ,affect+ ! ,int5sity ( ,s\nd4--,! int5sity ( s\nds is also affect$ by ! area ( ! vibrat+ body4 ,?is is %[n by sett+ a tun+ =k 9 vibration4 ,! area ( ! vibrat+ "p be+ small1 ! s\nd is he>d b a %ort di/ance f ! =k4 ,if1 h[ev]1 ! /em ( ! vibrat+ =k is press$ aga9/ ! panel ( a door or ! top ( a box1 ! s\nd may be he>d ?r\gh\t a room4 ,! /em ( ! =k has communicat$ its vibrations to ! wood4 ,! vibrat+ area1 be+ great]1 ! s\nd is !reby mu* increas$ 9 int5sity1 produc+ a wave ( great] amplitude4 ,! same pr9ciple is employ$ 9 ! s\nd+ bo>ds ( musical in/rum5ts z 9 ! piano1 viol91 etc4 ,x is a common obs]vation t s\nds decrease 9 l\dness z ! di/ance f ! s\rce increases4 ,?is is due to ! increase ( ! surface ( ! sph]ical s\nd waves spread+ 9 all directions f ! s\rce4 ,c>eful exp]im5ts h %[n t 9 a uni=m m$ium ! int5sity ( a s\nd is inv]sely proportional to ! squ>e ( ! di/ance f its s\rce4 ,if a s\nd is conf9$ s t x _c spread1 su* z ! s\nd mov+ ?r\gh a speak+ tube1 x ma9ta9s its int5sity = a consid]able di/ance4 ,an e> trumpet 7see ,fig4 #cbj7 also applies ?is pr9ciple4 ,x is con/ruct$ s t s\nd f a giv5 area is conc5trat$ by reflection to a mu* small] area ) a correspond+ increase 9 int5sity4 ,! megaphone 7,fig4 #cbc71 & ! speak+ trumpet />t ! s\nd waves ( ! voice 9 "o direction s t !y are kept f spread+ widely1 consequ5tly by its use ! voice may be he>d sev]al times ! usual di/ance4 ,! int5sity ( a s\nd is also affect$ by ! d5sity ( ! transmitt+ m$ium4 ,?us a s\nd produc$ on a m\nta9 top is fa9t] & ?9n] ?an "o produc$ 9 a valley4 ,! s\nd ( a bell 9 ! receiv] ( an air pump becomes weak] z ! air is exhau/$ f ! latt]4 ,f\r factors ?us influ5ce ! int5sity ( a s\nd1 ! area ( ! vibrat+ body1 its amplitude ( vibration1 ! di/ance ( ! s\rce & ! d5sity ( ! transmitt+ m$ium4 ,x is well to fix 9 m9d ! precise effect ( ea* ( ^! factors4 ,illu/ration3 ,,fig4 #cbc4--,! megaphone4 #cca4 ,pit*4--,! mo/ *>act]i/ic diff]5ce betwe5 musical s\nds is t ( pit*4 ,"s s\nds h a high pit*1 su* z ^? produc$ by _m insects & birds4 ,o!rs h a l[ pit* z ! notes ( a bass drum or ! s\nd ( ?und]4 ,h[ notes ( diff]5t pit* are produc$ may be %[n by ! sir5 7,fig4 #cbd74 ,?is is a disc m\nt$ s z to be rotat$ on an axis4 ,sev]al r[s ( holes are drill$ 9 x 9 conc5tric circles4 ,! numb] ( holes 9 successive r[s increases f )9 outw>d4 ,if :5 ! sir5 is rapidly rotat$ air is bl[n ?r\gh a tube aga9/ a r[ ( holes a cle> musical tone is he>d4 ,! tone is due to ! succession ( pulses 9 ! air produc$ by ! r[ ( holes 9 ! rotat+ disc alt]nately cutt+ (f & p]mitt+ ! air bla/ to pass ?r\gh at v %ort int]vals4 ,if ! bla/ is direct$ aga9/ a r[ ( holes ne>] ! circumf]5ce ! pit* is high]1 if aga9/ a r[ ne>] ! c5t] ! pit* is l[]4 ,or if ! bla/ is s5t aga9/ ! same r[ ( holes ! pit* rises :5 ! spe$ increases & l[]s :5 ! spe$ less5s4 ,^! facts indicate t ! pit* ( a tone is due to ! numb] ( pulses or vibrations t /rike ! e> ea* second2 also t ! great] ! rate ( vibration1 ! high] ! pit*4 ,illu/ration3 ,,fig4 #cbd4--;,a sir54 #ccb4 ,! ,major ,scale4--,if a sir5 is made ) eight r[s ( holes1 x may indicate ! relation betwe5 ! notes ( a major scale4 ,to accompli% ?is1 ! numb] ( holes 9 ! successive r[s %\ld be #bd1 #bg1 #cj1 #cb1 #cf1 #dj1 #de1 #dh4 ,if a disc s con/ruct$ is rapidly rotat$ at a uni=m rate1 a bla/ ( air s5t aga9/ all ( ! r[s 9 succession produces ! tones ( ! scale4 ,^! facts indicate t ! relative vibration numb]s ( ! notes ( any major scale h ! same relation z ! numb]s #bd1 #bg1 #cj1 #cb1 #cf1 #dj1 #de1 #dh4 ,! note call$ middle ,c is consid]$ by physici/s z hav+ #bef vibrations a second4 ,?is w\ld give ! foll[+ actual vibration numb]s to ! rema9+ notes ( ! major scale t beg9s ) ,middle ,c ,d4-#bhh1 ,e4-#cbj1 ,f4-#cda4c1 ,g4-#chd1 ,a4-#dbf4f1 ,b4-#dhj1 ,c'4-#eab4 ,musicians1 h[ev]1 usually make use ( a scale ( slightly high] pit*4 ,! int]national /&>d ( pit* 9 ?is c\ntry & 9 ,europe is t 9 :i* ,a has #dce vibrations p] second4 ,?is corresponds to #bfa vibrations = middle ,c4 #ccc4 ,! ,relation betwe5 ,spe$1 ,wave ,l5g?1 & ,numb] ( ,vibrations p] ,second4--,s9ce ! notes f ! v>i\s musical in/rum5ts ( an or*e/ra are notic$ to h>monize z well at a di/ance z at ! place produc$1 x is evid5t t notes ( all pit*es travel at ! same rate1 or h ! same spe$4 ,notes ( high pit*1 hav+ a high vibration rate produce m waves 9 a second ?an notes ( l[ pit*1 consequ5tly ! =m] are %ort] ?an ! latt]4 ,! foll[+ =mula gives ! relation betwe5 ! spe$ 7v71 wave l5g? 7l71 & numb] ( vibrations p] sec4 7n73 v l n1 or l v_/n t is1 ! spe$ ( a s\nd wave is equal to ! numb] ( vibrations p] second times ! wave l5g?1 or ! wave l5g? is equal to ! spe$ divid$ by ! numb] ( vibrations p] second4 ,?is =mula may also be employ$ to f9d ! numb] ( vibrations :5 ! wave l5g? & spe$ are giv54 ,important ,topics #a4 ,diff]5ce betwe5 noise & music4 #b4 ,factors affect+ int5sity3 area1 amplitude1 d5sity1 di/ance4 #c4 ,pit*1 major scale1 relative vibration numb]s4 #d4 ,relation betwe5 spe$1 wave l5g? & vibration rate4 ,ex]cises #a4 ,give an illu/ration f y\r own exp]i5ce ( ea* ( ! factors affect+ int5sity4 #b4 ,write ! relative vibration numb]s ( a major scale 9 :i* d has #abj vibrations4 #c4 ,:at is ! wave l5g? ( ! ,a ( int]national conc]t pit* at #be;,c48 ,compute 9 feet & c5timet]s4 #d4 ,at :at temp]ature w s\nd waves 9 air 9 unison ) ,middle ,c be exactly #d ft4 long8 #e4 ,expla9 ! use ( a megaphone4 #f4 ,:at tone has waves #c ft4 long at #be;,c48 #g4 ,:at is ! purpose ( ! s\nd+ bo>d ( a piano8 #h4 ,two m5 are di/ant #ajjj & #cjjj ft4 respectively f a fog horn4 ,:at is ! relative int5sity ( ! s\nds he>d by ! two m58 #i4 ,! speak+ tone ( ! av]age man's voice has #afj vibrations p] second4 ,h[ long are ! waves produc$ by him at #bj;,c48 7#d7 ,,musical ,,scales ,,& ,,resonance #ccd4 ,a musical int]val ref]s to ! ratio betwe5 ! pit*es,o ( two notes z indicat$ by ! results ( ! sir5 exp]im5t4 ,! simple/ int]val1 or ratio betwe5 two notes is ! octave1 ,c'3,c1 or #b3a 7#dh3bd74 ,o!r important int]vals ) ! correspond+ ratios are ! fif?1 ,g3,c1 or #c3b 7#cf3bd72 ! six?1 ,a3,c1 or #e3c 7#dj3bd72 ! f\r?1 ,f3,c1 #d3c 7#cb3bd72 ! major ?ird1 ,e3,c1 or #e3d 7#cj3bd72 & ! m9or ?ird1 ,g3,e1 #f3e4 ,! int]val betwe5 any two notes may be det]m9$ by f9d+ ! ratio betwe5 ! vibration numb]s ( ! two notes4 ,?us1 if "o note is produc$ by #fjj vibrations a second & ano!r by #djj1 ! int]val is #c3b1 or a fif?1 & ?is w\ld be recogniz$ by a musician :o he>d ! notes s\nd$ toge!r or "o aft] ! o!r4 ,bel[ is a table ( musical nom5clatures1 %[+ v>i\s relations betwe5 ! notes ( ! major scale4 ,o ,pit* z us$ "h1 means vibration rate4 ,,table ,,( ,,musical ,,nom5clatures ---------------------------------------- ------------------------- ,"n ( note ,c ,d ,e ,f ,g ,a ,b ,c ----------------------------- ----- ----------------------------- ,frequ5cy 9 t]ms (n#i_/hn#e_/dn#d_/cn#c_/bn#e_/cn#ae_/hn# bn d ---------------------------------------- ------------------- ,int]vals #i_/h #aj_/i #af_/ae #i_/h #aj_/i #i_/h #af_/ae ---------------------------------------- ------------------- ,"n ( note 9 vocald re mi fa sol la ti d music ---------------------------------------- ------------------------- ,treble clef4 ,music ,bass clef4 ,music ---------------------------------------- ------------------------- ,int]national pit* ( treble clef #bfa #bic4f #cbf4c #cdh4 #cia4e #dce #dhi4d #ebb ---------------------------------------- ------------------------- ,sci5tific scale #bef #bhh #cbj #cda4c #chd #dbf4f #dhj #eab ---------------------------------------- ------------------------- ,relative vibration #bd #bg #cj #cb #cf #dj #de #dh numb]s ---------------------------------------- ------------------------- #cce4 ,major & ,m9or ,triads4--,! notes ,c1 ,e1 ,g 7d1 mi1 sol7 =m :at is call$ a major triad4 ,! relative vibration numb]s correspond+ are #bd1 #cj1 #cf4 ,^! 9 simple/ t]ms h ratios ( #d3e3f4 ,any ?ree o!r tones ) vibration ratios ( #d3e3f w also =m a major triad4 ,if ! octave ( ! l[] tone is add$1 ! f\r make a major *ord4 ,?us3 ,f1 ,a1 ,c 7fa1 la1 d71 #cb3dj3dh1 or #d3e3f1 also =m a major triad z d ,g1 ,b1 ,d 7sol1 ti1 re71 #cf3de3ed1 or #d3e3f4 ,inspection w %[ t ^! ?ree major triads comprise all ( ! tones ( ! major scale ,d be+ ! octave ( ,d4 ,x is1 !re=e1 said t ! major scale is bas$1 or built1 ^u ^! ?ree major triads4 ,! examples j giv5 indicate ! ma!matical basis = h>mony 9 music4 ,?ree notes hav+ vibration ratios ( #aj3ab3ae are call$ m9or triads4 ,^! produce a less pleas+ effect ?an ^? hav+ ratios ( #d3e3f4 #ccf4 ,! ,ne$ = ,%>ps & ,flats4--,we h consid]$ ! key ( ,c4 ,?is is repres5t$ ^u ! piano or organ by :ite keys only 7,fig4 #cbe74 ,n[ 9 ord] 7a7 to give v>iety to in/rum5tal selections1 & 7b7 to accommodate in/rum5ts to ! range ( ! human voice1 x has be5 necess>y to introduce o!r notes 9 musical in/rum5ts4 ,^! are repres5t$ by ! black keys ^u ! piano & organ & are kn[n z %>ps & flats4 ,to illu/rate ! necessity = ^! additional notes take ! major scale />t+ ) ,b4 ,?is w give vibration frequ5cies ( #bdj1 #bgj1 #cjj1 #cbj1 #cfj1 #djj1 #dej1 & #dhj4 ,! only :ite keys t may be us$ ) ?is scale are ,e #cbj & ,b #dhj vibrations4 ,s9ce ! second note on ?is scale requires #bgj vibrations ab\t halfway betwe5 ,c & ,d ! black key ,c %>p is ins]t$4 ,o!r notes mu/ be ins]t$ betwe5 ,d & ,e 7,d %>p71 betwe5 ,f & ,g 7,f %>p71 also ,g & ,a %>ps4 ,illu/ration3 ,,fig4 #cbe4--,section ( a piano keybo>d4 #ccg4 ,temp]$ ,scales4--,9 musical in/rum5ts ) fix$ notes1 su* z ! h>p1 organ1 or piano1 complications 7 e>ly recogniz$ :5 an attempt 0 made to adapt ^! in/rum5ts s t !y c\ld be play$ 9 all keys4 ,= ! vibration numb]s t w\ld give a p]fect major scale />t+ at ,c are n ! same z w give a p]fect major scale beg9n+ ) any o!r key4 ,9 us+ ! v>i\s notes z ! keynote = a major scale1 #gb diff]5t notes 9 ! octave w\ld be requir$4 ,?is w\ld make x m difficult = su* in/rum5ts z ! piano to be play$4 ,to avoid ^! complications z mu* z possible1 x has be5 f\nd necess>y to ab&on ! simple ratios betwe5 successive notes & to sub/itute ano!r ratio 9 ord] t ! vibration ratio betwe5 any two successive notes w be equal 9 e case4 ,! diff]5ces betwe5 semitones are aboli%$ s t1 = example1 ,c %>p & ,d flat become ! same tone in/ead ( two diff]5t tones4 ,su* a scale is call$ a temp]$ scale4 ,! temp]$ scale has #ac notes to ! octave1 ) #ab equal int]vals1 ! ratio betwe5 two successive notes be+ ! #b or #a4jei4 ,t is1 any vibration rate on ! temp]$ scale may be comput$ by multiply+ ! vibration rate ( ! prec$+ note by #a4jei4 ,:ile ?is is a necess>y arrangem5t1 !re is "s loss 9 p]fect h>mony4 ,x is = ?is reason t a qu>tette or *orus ( voices s++ )\t accompanim5t is (t5 m h>moni\s & satisfactory ?an :5 accompani$ ) an in/rum5t ( fix$ notes z ! piano1 s9ce ! simple h>moni\s ratios may be employ$ :5 ! voices are alone4 ,! imp]fection introduc$ by equal temp]am5t tun+ is illu/rat$ by ! foll[+ table3 ,c ,d ,e ,f ,g ,a ,b ,c ,p]fect ,scale ( ,c #bef4j #bhh4j #cbj4j #cda4c #chd4j #dbf4f #dhj4j #eab4j ,temp]$ ,scale #bef4j #bhg4c #cbb4e #cda4g #chc4f #dcj4e #dhc4c #eab4j #cch4 ,resonance4--,if two tun+ =ks ( ! same pit* are plac$ ne> ea* o!r1 & "o is set vibrat+1 ! o!r w soon be f\nd to be 9 vibration4 ,?is result is said to be due to sympa!tic vibration1 & is an example ( resonance 7,fig4 #cbf74 ,if wat] is p\r$ into a glass tube :ile a vibrat+ tun+ =k is held ov] its top1 :5 ! air column has a c]ta9 l5g? x w />t vibrat+1 re9=c+ /rongly ! s\nd ( ! tun+ =k4 7,see ,fig4 #cbg47 ,?is is also an example ( resonance4 ,^! & o!r simil> facts indicate t s\nd waves />t$ by a vibrat+ body w cause ano!r body ne> x to />t vibrat+ if ! two h ! same rate ( vibration4 ,mo/ p]sons w recall illu/rations ( ?is effect f _! own exp]i5ce4 ,illu/ration3 ,,fig4 #cbf4--,"o tun+ =k w vibrate 9 sympa?y ) ! o!r1 if !y h exactly equal rates ( vibration4 ,illu/ration3 ,,fig4 #cbg4--;,an air column ( ! prop] l5g? re9=ces ! s\nd ( ! tun+ =k4 #cci4 ,sympa!tic vibration is expla9$ z foll[s3 ,s\nd waves produce v slight motions 9 objects affect$ by !m2 if ! vibration ( a giv5 body is exactly 9 "t ) ! vibrations ( a giv5 s\nd ea* impulse ( ! s\nd wave w /rike ! body s z to increase ! vibratory motion ( ! latt]4 ,?is action cont9u+1 ! body soon acquires a motion suffici5t to produce audible waves4 ,a good illu/ration ( sympa!tic vibration is furni%$ by ! bell r+]1 :o times 8 pulls ^u ! bell rope ) ! vibration rate ( ! sw+ ( ! bell4 ,9 ! case ( ! resonant air column ov] :i* is held a vibrat+ tun+ =k 7see ,fig4 #cbh71 :5 ! prong ( ! =k />ts d[nw>d f #a to #b1 a cond5sation wave moves d[n to ! wat] surface & back j 9 "t to jo9 ! cond5sation wave above ! =k z ! prong beg9s to move f #b to #a2 also :5 ! prong />ts upw>d f #b to #a1 ! r>efaction produc$ "u x moves to ! bottom ( ! air column & back s z to jo9 ! r>efaction above ! =k z ! prong returns4 ,:ile ! prong is mak+ a s+le movem5t1 up or d[n1 x is pla9 t ! air wave moves twice ! l5g? ( ! op5 tube4 ,dur+ a complete vibration ( ! =k1 !re=e1 ! s\nd wave moves f\r times ! l5g? ( ! air column4 ,9 free air1 ! s\nd progresses a wave l5g? dur+ a complete vibration1 h5ce ! resonant air column is "o-f\r? ! l5g? ( ! s\nd wave to :i* x responds4 ,exp]im5ts ) tubes cf diff]5t l5g?s %[ t ! diamet] ( ! air column has "s effect ^u ! l5g? giv+ be/ resonance4 ,ab\t #be p] c5t4 ( ! diamet] ( ! tube mu/ be add$ to ! l5g? ( ! air column to make x j "o-f\r? ! wave l5g?4 ,! s\nd he>d 9 sea%ells & 9 o!r holl[ bodies is due to resonance4 ,vibrations 9 ! air too feeble to affect ! e> are int5sifi$ by sympa!tic vibration until !y c be he>d4 ,a tun+ =k is (t5 m\nt$ ^u a box call$ a resonator1 :i* conta9s an air column ( su* dim5sions t x re9=ces ! s\nd ( ! =k's sympa!tic vibration4 ,illu/ration3 ,,fig4 #cbh4--;,explanation ( resonance4 ,important ,topics #a4 ,musical int]vals3 octave1 six?1 fif?1 f\r?1 ?ird4 #b4 ,major *ord1 #d3e3f4 #c4 ,use ( %>ps & flats4 ,temp]$ scale4 #d4 ,resonance1 sympa!tic vibration1 explanation1 examples4 ,ex]cises #a4 ,:at is a major scale8 ,:y is a major scale said to be built ^u ?ree triads8 #b4 ,:y are %>ps & flats necess>y 9 music8 #c4 ,:at is ! temp]$ scale & :y is x us$8 ,:at in/rum5ts ne$ n use x8 ,:y8 #d4 ,m5tion two examples ( resonance or sympa!tic vibration f y\r own exp]i5ce out ( s*ool4 #e4 ,an air column #b ft4 long clos$ at "o end is resonant to :at wave l5g?8 ,:at numb] ( vibrations w ?is s\nd h p] second at #be;,c48 #f4 ,at #bd;,c4 ,:at l5g? ( air column clos$ at "o end w be resonant to a s\nd hav+ #bg vibrations a second8 #g4 ,a giv5 note has #cjj vibrations a second4 ,:at w be ! numb] ( vibrations ( its 7a7 octave1 7b7 fif?1 7c7 six?1 7d7 major ?ird8 #h4 ,9 ! viol9 or guit> :at takes ! place ( ! s\nd+ bo>d ( ! piano8 #i4 ,c y expla9 :y ! pit* ( ! bell on a locomotive rises z y rapidly approa* x & falls z y rec$e f x8 #aj4 ,d notes ( high or l[ pit* travel fa/]8 ,expla94 #aa4 ,an ,a tun+ =k on ! int]national scale makes #dce vibrations p] second4 ,:at is ! l5g? ( ! s\nd waves produc$8 7#e7 ,,wave ,,int]f]5ce1 ,,beats1 ,,vibration ,,( ,,/r+s #cdj4 ,int]f]5ce ( waves4--,! possibility ( two tra9s ( waves comb9+ s z to produce a r$uc$ motion or a complete de/ruction ( motion may be %[n graphically4 ,suppose two tra9s ( waves ( equal wave l5g? & amplitude z 9 ,fig4 #cbi meet 9 opposite phases4 ,t is1 ! p>ts correspond+ to ! cre/s ( ,a co9cide ) ! tr\ghs ( ,b1 also ! tr\ghs ( ,a ) ! cre/s ( ,b2 :5 ?is condition obta9s1 ! result is t %[n at ,c1 ! union ( ! two waves result+ 9 complete de/ruction ( motion4 ,! m or less complete de/ruction ( "o tra9 ( waves by ano!r simil> tra9 is an illu/ration ( int]f]5ce4 ,if two sets ( wat] waves s unite z to entirely de/roy ea* o!r ! result is a level wat] surface4 ,if two tra9s ( s\nd waves comb9e !y may s int]f]e t sil5ce results4 ,! conditions = secur+ int]f]5ce ( s\nd waves may readily be secur$ by us+ a tun+ =k & a resonat+ air column4 ,if ! tun+ =k is set vibrat+ & plac$ ov] ! op5 end ( ! resonat+ air column 7see ,fig4 #cbh71 an increase 9 ! s\nd ?r\gh resonance may be he>d4 ,if ! =k is rotat$ ab\t its axis1 9 "s positions no s\nd is he>d :ile 9 o!r positions ! s\nd is /rongly re9=c$4 ,simil> effects may be p]ceiv$ by hold+ a vibrat+ =k ne> ! e> & sl[ly rotat+ z be=e4 ,9 "s positions int]f]5ce results :ile 9 o!r positions ! s\nd is pla9ly he>d4 ,! explanation ( int]f]5ce may be made cle> by ! use ( a diagram4 7,see ,fig4 #ccj47 ,let u imag9e t we are look+ at ! two squ>e ends ( a tun+ =k4 ,:5 ! =k is vibrat+ ! two prongs approa* ea* o!r & !n rec$e4 ,z !y approa*1 a cond5sation is produc$ at #b & r>efactions at #a & #c4 ,z !y sep>ate1 a r>efaction is produc$ at #b & cond5sations at #a & #c4 ,n[ along ! l9es at :i* ! simultane\sly produc$ r>efactions & cond5sations meet !re is m or less complete int]f]5ce4 7,see ,fig4 #cca47 ,^! positions h be5 indicat$ by dott$ l9es ext5d+ ?r\gh ! ends ( ! prongs4 ,z indicat$ above1 ^! positions may be easily f\nd by rotat+ a vibrat+ =k ov] a resonant air column1 or ne> ! e>4 ,illu/ration3 ,,fig4 #cbi4--;,int]f]5ce ( s\nd waves4 ,illu/ration3 ,,fig4 #ccj4--;,at #b is a cond5sation2 at #a & #c are r>efactions4 ,illu/ration3 ,,fig4 #cca4--,! cond5sations & r>efactions meet along ! dott$ l9es produc+ sil5ce4 ,illu/ration3 ,,fig4 #ccb4--;,diagram illu/rat+ ! =mations ( beats4 #cda4 ,beats4--,if two tun+ =ks ( slightly diff]5t pit* are set vibrat+ & plac$ ov] resonat+ air columns or ) ! /em ( ea* =k ^u a s\nd+ bo>d1 s t ! s\nds may be int5sifi$1 a peculi> pulsation ( ! s\nd may be notic$4 ,?is ph5om5on is kn[n z beats4 ,its production may be easily und]/ood by consid]+ a diagram 7,fig4 #ccb74 ,let ! curve ,a repres5t ! s\nd wave s5t out by "o tun+ =k & ,b1 t s5t out by ! o!r4 ,c repres5ts ! effect produc$ by ! comb9ation ( ^! waves4 ,at ,r ! two s\nd waves meet 9 ! same phase & re9=ce ea* o!r4 ,?is results 9 a l\d] s\nd ?an ei!r produces alone4 ,n[ s9ce ! s\nds are ( slightly diff]5t pit*1 "o =k s5ds out a few m vibrations p] second ?an ! o!r4 ,! waves f ! fir/ =k are !re=e a little %ort] ?an ^? f ! o!r4 ,consequ5tly1 al?\gh ! two waves are at "o "t 9 ! same phase1 !y mu/ soon be 9 opposite phases z at ,i4 ,"h int]f]5ce occurs1 & sil5ce results4 ,imm$iately ! waves re9=ce1 produc+ a l\d] s\nd & s on alt]nately4 ,! result+ rise & fall ( ! s\nd are kn[n z beats4 ,! numb] ( beats p] second mu/1 ( c\rse1 be ! same z ! diff]5ce betwe5 ! numb]s ( vibrations p] second ( ! two s\nds4 ,"o effect ( beats is discord4 ,?is is especially noticeable :5 ! numb] ( beats p] second is betwe5 #cj & #abj4 ,/rike ! two l[e/ notes on a piano at ! same "t4 ,! beats are v noticeable4 ,illu/ration3 ,,fig4 #ccc4--,turki% cymbals4 ,illu/ration3 ,,fig4 #ccd4--,! cornet4 #cdb4 ,?ree ,classes ( ,musical ,in/rum5ts4--,!re are ?ree classes or gr\ps ( musical in/rum5ts1 if we consid] ! vibrat+ body t produces ! s\nd 9 ea*3 7,a7 ,^? 9 :i* ! s\nd is produc$ by a vibrat+ plate or membrane1 z ! drum1 cymbals 7,fig4 #ccc71 etc42 7,b7 ^? ) vibrat+ air columns1 z ! flute1 pipe organ1 & cornet 7,fig4 #ccd71 & 7,c7 ) vibrat+ wires or /r+s1 z ! piano1 viol91 & guit>4 ,x is wor? :ile to consid] "s ( ^! c>efully4 ,we w beg9 ) a consid]ation ( vibrat+ wires & /r+s1 ^! (t5 produc+ tones ( ri* quality4 ,let u consid] ! /r+s ( a piano4 7,if possible1 look at ! /r+s 9 "s in/rum5t47 ,! range ( ! piano is #g-a_/c octaves4 ,its l[e/ note1 ,a#d1 has ab\t #bg vibrations p] second4 ,its highe/1 ,c1 ab\t #dagf4 ,?is great range 9 vibration rate is secur$ by v>y+ ! l5g?1 ! t5sion1 & ! diamet] ( ! /r+s4 #cdc4 ,! ,laws ( ,vibrat+ ,/r+s4--,! relations betwe5 ! vibration rate1 ! l5g?1 ! t5sion & ! diamet]1 ( vibrat+ /r+s h be5 c>efully /udi$ ) an in/rum5t call$ a sonomet] 7,fig4 #cce74 ,by ?is device x is f\nd t ! pit* ( a vibrat+ /r+ is rais$ "o octave :5 its vibrat+ l5g? is r$uc$ to "o-half4 ,by det]m9+ ! vibration rate ( _m l5g?s1 ! foll[+ law has be5 d]iv$3 7,law ,i7 ,! rate ( vibration ( a /r+ is inv]sely proportional to its l5g?4 ,illu/ration3 ,,fig4 #cce4--;,a sonomet]4 ,c>eful te/s ^u ! *ange ( vibration rate produc$ by a *ange ( t5sion or pull ^u ! /r+s %[ t if ! pull is increas$ f\r times its vibrations rate is d\bl$1 & if x is increas$ n9e times its rate is tripl$1 t is3 7,law ,,ii7 ,! vibration rates ( /r+s are directly proportional to ! squ>e roots ( _! t5sions4 ,te/s ( ! effects ( diamet] are made by tak+ wires ( equal l5g? & t5sion & ( ! same mat]ial b ( diff]5t diamet]4 ,suppose "o is twice z ?ick z ! o!r4 ,?is /r+ has a tone an octave l[] or vibrates "o-half z fa/ z ! fir/4 ,!re=e3 7,law ,,iii7 ,! vibration rates ( /r+s are inv]sely proportional to ! diamet]s4 ,^! laws may be express$ by a =mula n 7t7_/dl4 ,! vibration ( a /r+ is r>ely a simple matt]4 ,x usually vibrates 9 p>ts at ! same "t t x is vibrat+ z a :ole4 ,! tone produc$ by a /r+ vibrat+ z a :ole is call$ its fundam5tal4 ,! vibrat+ p>ts ( a /r+ are call$ loops or segm5ts 7see ,fig4 #ccf71 :ile ! po9ts ( lea/ or no vibration are nodes4 ,segm5ts are (t5 call$ ant9odes4 ,illu/ration3 ,,fig4 #ccf4--;,a /r+ yield+ its fundam5tal & its fir/ ov]tone4 #cdd4 ,ov]tones4--,! quality ( ! tone produc$ by a vibrat+ /r+ is affect$ by its vibration 9 p>ts :5 x is also vibrat+ z a :ole4 7,see ,fig4 #ccf47 ,! tones produc$ by ! vibration 9 p>ts are call$ ov]tones or p>tial tones4 ,! pres5ce ( ^! ov]tones may (t5 be detect$ by ! sympa!tic vibration ( o!r wires ne>-by4 ,:at is call$ ! fir/ ov]tone is produc$ by a /r+ vibrat+ 9 two p>ts1 ! second ov]tone by a /r+ vibrat+ 9 ?ree p>ts1 ! ?ird ov]tone by its vibration 9 f\r p>ts & s on4 ,9 any ov]tone1 ! numb] ( ! p>ts or vibrat+ segm5ts ( ! /r+ is "o m ?an ! numb] ( ! ov]tone4 ,= example1 g5tly press d[n ! key ( middle ,c ( a piano4 ,?is w leave ! /r+ free to vibrate4 ,n[ /rongly /rike ! ,c an octave l[] & !n remove ! f+] f ?is key4 ,! middle ,c /r+ w be he>d giv+ its tone4 ,9 l mann] try ,e & ,g1 ) ,c4 ,?is exp]im5t %[s t ! s\nd ( ! ,c /r+ conta9s ^! tones z ov]tones4 ,x also illu/rates sympa!tic vibration4 ,important ,topics #a4 ,int]f]5ce1 beats1 production1 effects4 #b4 ,vibration ( /r+s1 ?ree laws4 #c4 ,?ree classes ( musical in/rum5ts4 #d4 ,fundam5tal & ov]tones1 nodes1 segm5ts1 h[ produc$8 ,results4 ,ex]cises #a4 ,:at diff]5t means are employ$ to produce v>iation ( ! pit* ( piano /r+s8 ,= viol9 /r+s8 #b4 ,h[ _m beats p] second w be produc$ by two tun+ =ks hav+ #eab & #eji vibrations p] second respectively8 #c4 ,a wire #ahj cm4 long produces middle ,c4 ,%[ by a diagram1 us+ numb]s1 :]e a bridge w\ld h to be plac$ to cause ! /r+ to emit ea* tone ( ! major scale4 #d4 ,h[ c a viol9i/ play a tune on a s+le /r+8 #e4 ,:at are ! frequ5cies ( ! fir/ #e ov]tones ( a /r+ ^: fundam5tal gives #bef vibrations p] second8 #f4 ,"o p]son takes #aab /eps a m9ute & ano!r #aaf4 ,h[ _m times a m9ute w ! two walk]s be 9 /ep8 ,h[ _m times a m9ute w "o be advanc+ ! left foot j :5 ! o!r advances ! "r8 #g4 ,:y is x necess>y to h a /&>d pit*8 #h4 ,h[ c ! pit* ( ! s\nds giv5 by a phonograph be l[]$8 #i4 ,h[ _m beats p] second w occur :5 two tun+ =ks hav+ frequ5cies ( #eab & #eae respectively1 are s\nd$ toge!r8 #aj4 ,:i* wires ( a piano give ! highe/ pit*8 ,:y8 7#f7 ,,tone ,,quality1 ,,vibrat+ ,,air ,,columns1 ,,plates #cde4 ,quality4--,! reason = ! diff]5ces 9 tone quality betwe5 notes ( ! same pit* & int5sity z produc$1 e4g41 by a viol9 & a piano1 0 long a matt] ( conjecture4 ,helmholtz1 a ,g]man physici/ 7see p4 #cig7 fir/ def9itely prov$ t tone quality is due to ! v>i\s ov]tones pres5t along ) ! fundam5tal & _! relative int5sities4 ,if a tun+ =k is fir/ set vibrat+ by draw+ a b[ across x & !n by /rik+ x ) a h>d object1 a diff]5ce 9 ! quality ( ! tones produc$ is noticeable4 ,x is ?us evid5t t ! mann] ( sett+ a body 9 vibration affects ! ov]tones produc$ & ?us ! quality4 ,piano /r+s are /ruck by felt hamm]s at a po9t ab\t "o-sev5? ( ! l5g? ( ! /r+ f "o end4 ,?is po9t has be5 select$ by exp]im5t1 x hav+ be5 f\nd to yield ! be/ comb9ation ( ov]tones z %[n by ! quality ( ! tone result+4 ,illu/ration3 ,,fig4 #ccg4--;,*ladni's plate4 ,illu/ration3 ,,fig4 #cch4--;,*ladni's figures4 #cdf4 ,*ladni's ,plate4--,! fact t vibrat+ bodies are capable ( _m modes ( vibration is well illu/rat$ by :at is kn[n z ,*ladni's plate4 ,?is consi/s ( a circul> or squ>e %eet ( brass atta*$ to a /& at its c5t] s z to be held horizontally4 7,see ,fig4 #ccg47 ,f9e s& is spr9kl$ ov] its surface & ! disc is set vibrat+ by draw+ a viol9 b[ across its edge4 ,! mode ( vibration ( ! disc is indicat$ by ! s& accumulat+ along ! l9es ( lea/ vibration1 call$ nodal l9es4 ,a v>iety ( nodal l9es ea* accompani$ by its *>act]i/ic tone may be obta9$ by *ang+ ! position ( ! b[ & by t\*+ ! f+]s at diff]5t po9ts at ! edge ( ! disc4 ,!y are kn[n z ,*ladni's figures4 7,see ,fig4 #cch47 ,illu/ration3 ,,fig4 #cci4--,manometric flame app>atus4 #cdg4 ,manometric ,flames4--,! actual pres5ce ( ov]tones along ) ! fundam5tal may be made visible by ! manometric flame app>atus4 ,?is consi/s ( a wood5 box1 ,c1 m\nt$ ^u a /&4 7,see ,fig4 #cci47 ,! box is divid$ v]tically by a flexible p>tition or diaphragm4 ,two outlets are provid$ on "o side ( ! p>tition1 "o1 ,c1 leads to a gas pipe1 ! o!r is a glass tube1 ,d4 ,on ! o!r side ( ! p>tition a tube1 ,e1 leads to a m\?piece4 ,a mirror1 ,m1 is m\nt$ s z to be rotat$ ^u a v]tical axis 9 front ( ,f & ne> x4 ,gas is n[ turn$ on & light$ at ,f4 ,! s\nd ( ! voice produc$ at ! m\?piece s5ds s\nd waves ?r\gh ! tube & aga9/ ! diaphragm :i* vibrates back & =? z ! s\nd waves /rike x4 ,?is action affects ! flame :i* rises & falls4 ,if n[ ! mirror is rotat$1 ! image ( ! flame se5 9 ! mirror rises & falls1 %[+ n only ! fundam5tal or pr9cipal vibrations b also ! ov]tones4 ,if ! diff]5t v[el s\nds are utt]$ 9 succession 9 ! m\?piece1 ea* is f\nd to be accompani$ by its *>act]i/ic wave =m 7,fig4 #cdj74 ,9 "s1 ! fundam5tal is /rongly prom95t1 :ile 9 o!rs1 ! ov]tones produce m>k$ modifications4 ,o!r devices h be5 inv5t$ :i* make possible ! accurate analysis ( s\nds into _! compon5t vibrations1 :ile /ill o!rs unite simple tones to produce any complex tone desir$4 #cdh4 ,! ,phonograph4--,! graphophone or phonograph provides a me*anism = cutt+ ^u a disc or cyl9d] a groove t reproduces1 9 ! v>y+ =m or dep? ( ! trac+1 e peculi>ity ( ! s\nd waves affect+ x4 ,! reproduc] consi/s ( a s5sitive diaphragm to :i* is atta*$ a ne$le4 ,! disc or cyl9d] is rotat$ "u ! reproduc+ ne$le4 ,! irregul>ities ( ! bottom ( ! trac+ cause correspond+ movem5ts ( ! ne$le & ! atta*$ diaphragm1 :i* />t waves t reproduce ! s\nds t previ\sly affect$ ! record]4 ,! con/ruction ( ! phonograph has rea*$ su* p]fection t v accurate reproduction ( a great v>iety ( s\nds is secur$4 ,illu/ration3 ,,fig4 #cdj4--;,*>act]i/ic =ms ( manometric flames4 #cdi4 ,w9d ,in/rum5ts4--,9 _m musical in/rum5ts z ! cornet1 pipe-organ1 flute1 etc41 & also 9 :i/les1 ! vibrat+ body t s]ves z a s\rce ( s\nd is a column ( air1 usually enclos$ 9 a tube4 ,unlike vibrat+ /r+s1 ?is vibrat+ s\rce ( s\nd *anges b little 9 t5sion or d5sity1 h5ce *anges 9 ! pit* ( air columns is secur$ by *ang+ _! l5g?4 ,! law be+ simil> to t ) /r+s1 ! vibration rates ( air columns are inv]sely proportional to _! l5g?s4 ,illu/ration3 ,,fig4 #cda4--7,r7 ,cross-section ( an organ pipe %[+ action ( tongue at ,c4 7a7 ,! fundam5tal tone 9 a clos$ pipe has a wave l5g? f\r times ! l5g? ( ! pipe2 7b7 & 7c7 h[ ! fir/ & second ov]tones are =m$ 9 a clos$ pipe2 7d7 ! fundam5tal tone ( an op5 pipe has a wave l5g? equal to twice ! l5g? ( ! pipe2 7e7 & 7f7 fir/ & second ov]tones ( op5 pipe4 ,if an op5 organ pipe be s\nd$ by bl[+ g5tly ?r\gh x1 a tone ( def9ite pit* is he>d4 ,n[ if "o end is clos$1 on be+ s\nd$ aga9 ! pit* is f\nd to be an octave l[]4 ,!re=e1 ! pit* ( a clos$ pipe is an octave l[] ?an t ( an op5 "o ( ! same l5g?4 #cej4 ,nodes 9 ,organ ,pipes4--,fig4 #cda1 ,r repres5ts a cross-section ( a wood5 organ pipe4 ,air is bl[n ?r\gh ,a1 & /rikes aga9/ a ?9 tongue ( wood ,c4 ,?is />ts ! jet ( air vibrat+ ?us sett+ ! column ( air 9 vibration s t ! s\nd is kept up z long z air is bl[n ?r\gh ,a4 ,to und]/& ! mode ( vibration ( ! air column a /udy ( ! curve t repres5ts wave motion 7,fig4 #cdb7 is helpful ,let ,,ab repres5t su* a curve1 9 ?is #b1 #d & #f repres5t nodes or po9ts ( lea/ vibration1 :ile #a1 #c & #e are ant9odes or places ( greate/ motion4 ,a full wave l5g? ext5ds f #a-e1 or #b-f4 ,n[ 9 ! op5 organ pipe 7,fig4 #cda;d71 ! end ( ! air column d is a place ( great vibration or is an ant9ode4 ,at ! o!r end also occurs ano!r place ( great vibration or an ant9ode2 betwe5 ^! two ant9odes mu/ be a place ( lea/ vibration or a node4 ,! op5 air column !re=e ext5ds f ant9ode to ant9ode 7or f #a-c7 or is "o-half a wave l5g?4 ,! clos$ air column 7,fig4 #cda;a7 ext5ds f a place ( great vibration at a to a place ( no vibration at ! clos$ end4 ,! di/ance f an ant9ode to a node is t f #a-b on ! curve & is "o-f\r? a wave l5g?4 ,illu/ration3 ,,fig4 #cdb4--;,graphic repres5tation ( s\nd waves4 ,illu/ration3 ,,fig4 #cdc4--;,a cl>9et4 ,:5 a pipe is bl[n /rongly x yields ov]tones4 ,! bugle is a musical in/rum5t 9 :i* notes ( diff]5t pit* are produc$ by diff]5ces 9 bl[+4 7,see ,fig4 #cda47 7d71 7e71 7f74 ,9 play+ ! cornet diff]5t pit*es are produc$ by diff]5ces 9 bl[+1 & by valves :i* *ange ! l5g? ( ! vibrat+ air column4 7,see ,fig4 #ccd47 ,! cl>9et has a m\?piece conta9+ a re$ simil> to t made by cutt+ a tongue on a /raw or quill4 ,! l5g? ( ! vibrat+ air column 9 ! cl>9et is *ang$ by op5+ holes 9 ! sides ( ! tube4 7,see ,fig4 #cdc47 #cea4 ,h[ we ,he>4--,our he>+ app>atus is arrang$ 9 ?ree p>ts4 7,see ,fig4 #cdd47 ,! ext]nal e> leads to ! tympanum4 ,! middle e> conta9s ?ree bones t convey ! vibrations ( ! tympanum to ! int]nal e>4 ,! latt] is fill$ ) a liquid :i* conveys ! vibrations to a "p hav+ a coil$ %ell-l /ructure call$ ! ,co*lea4 ,/ret*$ across )9 ! co*lea are "s #cjjj fib]s or /r+s4 ,x is believ$ t ea* is s5sitive to a p>ticul> vibration rate & t ea* is also atta*$ to a n]ve fib]4 ,! s\nd waves ( ! air transmitt$ by ! tympanum1 ! e> bones & ! liquid ( ! int]nal e> />t sympa!tic vibrations 9 ! /r+s ( ! co*lea :i* affect ! auditory n]ve & we he>4 ,! highe/ tones p]ceptible by ! human e> are produc$ by f #bd1jjj to #dj1jjj vibrations p] second4 ,! av]age p]son _c he> s\nds produc$ by m ?an ab\t #bh1jjj vibrations4 ,! usual range ( he>+ is ab\t #aa octaves4 ,! tones produc$ by high] vibrations ?an ab\t #dajj p] second are %rill & displeas+4 ,9 music ! range is #g-a_/c octaves1 ! l[e/ tone be+ produc$ by #bg4e vibrations1 ! highe/ by ab\t #dajj p] second4 ,illu/ration3 ,,fig4 #cdd4--,! human e>4 ,! tones produc$ by m5 are l[] ?an ^? ( wom5 & boys4 ,9 m5 ! vocal cords are ab\t #ah mm4 long2 9 wom5 !y are #ab mm4 long4 ,! compass ( ! human voice is ab\t two octaves1 al?\gh "s not$ s+]s h a range ( two & "o-half octaves4 ,9 ord9>y conv]sation ! wave l5g? ( s\nds produc$ by a man's voice is f #h to #ab ft4 & t ( a woman's voice is f #b to #d ft4 ,important ,topics #a4 ,tone quality4 ,fundam5tal & ov]tones4 ,*ladni's plate4 #b4 ,manometric flame app>atus4 #c4 ,phonograph record] & reproduc]4 #d4 ,air columns & w9d in/rum5ts4 #e4 ,h[ we he>4 ,ex]cises #a4 ,:at det]m9es ! pit* ( ! note ( a toy :i/le8 #b4 ,! l[e/ note ( ! organ has a wave l5g? ( ab\t #fd ft4 ,:at is ! l5g? ( a clos$ pipe giv+ ?is note8 ,( an op5 pipe8 #c4 ,:at is ! fir/ ov]tone ( ,c8 ,:at are ! second & ?ird ov]tones8 ,give vibration numb]s & pit* names or lett]s4 #d4 ,:y is ! music ( a b& j z h>moni\s at a di/ance ( #djj ft4 z at #ajj ft48 #e4 ,a resonant air column #fj cm4 long clos$ at "o end w respond to :at rate ( vibration at #aj;,c48 #f4 ,c y f9d out h[ ! valves on a cornet op]ate to *ange ! pit* ( ! tone8 #g4 ,h[ is ! trombone op]at$ to produce tones ( diff]5t pit*8 #h4 ,! l[e/ note on an organ has a wave l5g? ( ab\t #fd ft4 ,:at mu/ be ! l5g? ( a clos$ pipe giv+ ?is note8 #i4 ,:at is ! approximate l5g? ( an op5 organ pipe :i* s5ds out waves #d ft4 long8 ,review ,outl9e3 ,s\nd ,s\nd--def9ition1 s\rce1 m$ium1 spe$1 nature4 ,waves--longitud9al1 transv]se1 illu/rations4 ,*>act]i/ics ( int5sity--area1 amplitude1 d5sity1 di/ance4 ,musical ,s\nds3 pit*--scales2 major1 temp]$1 triads1 ,n ,v_/,l quality--fundam5tal & ov]tones4 ,sympa!tic ,vibrations--resonance1 int]f]5ce1 beats1 discord4 ,musical ,in/rum5ts--/r+1 air column1 membrane or plate4 ,laws (2 7a7 vibrat+ /r+s 7#c71 7b7 vibrat+ air columns 7#b74 ,,*apt] ,,xvi ,,light 7#a7 ,,light1 ,,its ,,rectil9e> ,,propagation1 ,,%ad[s #ceb4 ,a ,comp>ison ( ,s\nd & ,light4--,light f ! /&po9t ( physics is consid]$ mu* z is s\nd1 z a mode ( motion2 "o affect+ ! e>1 ! o!r produc+ ! result call$ vision4 ,!re are o!r diff]5ces also wor? consid]+4 7a7 ,:ile s\nd travels z vibrations ( "s mat]ial m$ium1 light travels only z vibrations ( ! e!r2 solids1 liquids1 & gases act s z to h9d] r ?an to assi/ 9 its movem5t4 ,t is1 light travels be/ 9 a vacuum or 9 a space devoid ( ord9>y matt]4 7b7 ,! spe$ ( light is s great t at ord9>y di/ances on ! e>? its motion is practically in/antane\s4 ,exp]im5ts h %[n t its spe$ is ab\t #ahf1jjj miles to #cjj1jjj kilomet]s a second4 #cec4 ,lum9\s & ,illum9at$ ,bodies4--,if we consid] ! objects )9 a room1 "s ( !m1 z books & furniture1 w\ld be invisible if all light f ext]nal s\rces 7 exclud$4 ,on ! o!r h&1 "s o!r objects1 su* z a light$ lamp1 a burn+ coal1 or a r$ hot iron1 w\ld be se5 if no outside light 7 pres5t4 ,su* bodies are said to be lum9\s4 ,mo/ lum9\s bodies are hot & become non-lum9\s on cool+4 ,!re are1 h[ev]1 "s bodies t are lum9\s at ord9>y room temp]atures1 z ! firefly & "s phosphoresc5t pa9ts4 ,:5 light emitt$ by a lum9\s body /rikes an object1 a portion ( x is always reflect$4 ,x is ?is reflect$ light t makes ! illum9at$ object visible4 ,if ! object is a %eet ( glass1 "s ( ! light is transmitt$4 ,if a sub/ance is s cle> t objects c be se5 ?r\gh x1 ! sub/ance is transp>5t1 b if objects _c be se5 ?r\gh x1 ! sub/ance is said to be transluc5t4 ,objects transmitt+ no light are opaque4 ,"s ( ! light fall+ ^u a body is nei!r reflect$ nor transmitt$1 b is absorb$ & t5ds to w>m ! body4 ,! light fall+ ^u a body is !re=e ei!r reflect$1 transmitt$1 or absorb$4 ,?us ,fig4 #cde repres5ts light com+ f ,s to a piece ( glass ,,gl4 ,a portion ( ! light repres5t$ by ,r is reflect$4 ,ano!r "p ,a is absorb$ & disappe>s1 :ile /ill ano!r "p ,t is transmitt$ & passes on4 ,illu/ration3 ,,fig4 #cde4--,! light is transmitt$ 7,t71 reflect$ 7,r71 or absorb$ 7,a74 ,!re is no %>ply drawn l9e betwe5 transp>5t & opaque bodies4 ,v ?9 %eets ( gold transmit a gre5i% light1 & exp]im5ts h %[n t sub/ances z transp>5t z cle> wat] absorb en\gh light s t at consid]able dep?s 9 an ocean or lake little or no light is ev] f\nd4 ,all light :e!r f lum9\s bodies or reflect$ f non-lum9\s objects %[s c]ta9 prop]ties :i* w n[ be consid]$4 #ced4 ,! ,rectil9e> ,propagation ( ,light4--,if a beam ( light passes ?r\gh a hole 9 a w9d[ %ade into a d>k5$ room1 x is se5 to foll[ a p]fectly /raight c\rse4 ,if a p]son :ile c\gh+ holds a book be=e ! face1 ! s\nd passes ar\nd ! book & is he>d at any po9t 9 ! room :ile ! face is hidd5 by ! book4 ,9 o!r words1 light ord9>ily does n pass ar\nd corn]s z s\nd does1 b travels 9 /raight l9es4 ,?is fact is made use ( :5 "o aims a gun or m]ely looks at an object4 ,s well e/abli%$ 9 our m9ds is ! idea t an object is 9 ! direction f :i* we see ! light com+ to u f x1 t we are sometimes deceiv$ z to ! real position ( an object1 :5 ! c\rse ( ! light f x has be5 *ang$ by a mirror or "s o!r reflect+ surface4 ,_m illusions are produc$ 9 ?is way1 ( :i* ! mirage ( ! des]t is "o example4 7,see ,art4 #cha47 ,illu/ration3 ,,fig4 #cdf4--,%ad[ f a small s\rce ( light4 ,illu/ration3 ,,fig4 #cdg4--,%ad[ :5 s\rce ( light is l>ge4 #cee4 ,%ad[s4--,a %ad[ is ! space f :i* light is cut (f by an opaque body4 ,?us if a book 7see ,fig4 #cdf7 is held betwe5 a scre51 ,n1 & a small s\rce ( light1 ,l1 a %ad[ is produc$ :i* ext5ds f ! book to ! scre54 ,notice t ! %ad[ is a space & n an area4 ,if a l>ge gas flame 7see ,fig4 #cdg7 is us$ z ! s\rce ( light1 ! %ad[ ( ! book is no long] cle> cut at ! edges z be=e1 b has a d>k] c5tral "p ) a light] fr+e ( p>tial %ad[ at ! edges4 ,! d>k portion )9 ! %ad[ has all ! light exclud$ f x & is call$ ! umbra4 ,! light] portion ( ! %ad[ at ! edges has only a "p ( ! light f ! flame cut (f4 ,?is portion is call$ ! p5umbra4 :5 "o /&s 9 sunlight 8 %ad[ ext5ds f 8 body to ! gr\nd or object on :i* ! %ad[ falls4 ,at night we are 9 ! e>?'s %ad[1 :i* ext5ds out into space beyond ! e>?4 ,illu/ration3 ,,fig4 #cdh4--;,"* ( ! e>?'s %ad[4 #cef4 ,eclipses4--,s9ce ! sun is a v l>ge object ! %ad[ ca/ by ! e>? conta9s bo? umbra & p5umbra4 7,see ,fig4 #cdh47 ,:5 ! moon passes into ! %ad[ ( ! e>?1 !re is said to be an eclipse ( ! moon1 :ile if ! moon's %ad[ falls ^u ! e>?1 ! portion ( ! e>? cut (f f ! sun's light has an eclipse ( ! sun4 #ceg4 ,images by ,small ,ap]tures4--,! /raight l9e movem5t ( light makes possible ! p9-hole cam]a1 by :i* satisfactory photographs h be5 made4 ,! action ( ?is device may be illu/rat$ by plac+ a lum9\s body1 a light$ c&le1 an inc&esc5t lamp1 or a gas flame1 9 front ( a piece ( c>dbo>d1 ,s1 :i* has a small op5+ 9 x4 ,light f ! object 7see ,fig4 #cdi7 falls ^u a scre51 ,s#b1 s z to produce an inv]t$ image4 ,o!r applications ( ?is pr9ciple w be giv5 lat]4 ,9 ,fig4 #cdi let ,,pq repres5t a gas flame1 !n light f po9t ,p at ! top ( ! flame w pass 9 a /raight l9e ?r\gh ! op5+ or ap]ture ( ! c>dbo>d & /rike at ,p#b at ! bottom ( ! illum9at$ spot ^u ! scre54 ,light f ,q pass+ 9 /raight l9es ?r\gh ! ap]ture w /rike at ,q#b at ! top ( ! light$ space4 ,?is spot ( light w h ! same outl9es z ! lum9\s body ,,pq & be+ =m$ z j describ$ w be inv]t$4 ,illu/ration3 ,,fig4 #cdi4--;,image =m$ by a small ap]ture is inv]t$4 ,?is spot ( light1 resembl+ 9 its outl9es ! flame1 is call$ an image4 ,an image is def9$ z an optical c\nt]p>t ( an object4 ,images are =m$ 9 a v>iety ( devices1 su* z ap]tures1 mirrors1 & l5ses4 ,! p9-hole cam]a is simply a light-tight box ) a small ap]ture 9 "o side4 ,light pass+ ?r\gh ?is ap]ture =ms an image ^u ! opposite side ( ! int]ior ( ! box1 ( :atev] object is 9 front ( ! cam]a4 ,light ent]+ a room ?r\gh a l>ge ap]ture su* z a w9d[ produces a multitude ( ov]lapp+ images :i* bl5d to =m a some:at ev5ly illum9at$ surface4 ,important ,topics #a4 ,light contra/$ ) s\nd 7?ree diff]5ces74 #b4 ,bodies3 transp>5t1 transluc5t1 opaque4 #c4 ,light3 reflect$1 transmitt$1 absorb$4 #d4 ,light travels 9 /raight l9es1 evid5ce1 %ad[s1 umbra1 p5umbra4 #e4 ,=mation ( images by small ap]tures4 ,ex]cises #a4 ,consid] ! circumf]5ce ( ! e>? z #be1jjj miles4 ,h[ _m times w\ld ! spe$ ( light cov] ?is di/ance 9 a second8 #b4 ,h[ soon aft] any great di/urbance takes place on ! sun1 #ic1jjj1jjj miles di/ant1 c x be se5 ^u ! e>?8 #c4 ,con/ruct a diagram ( ! moon's %ad[4 ,h[ mu* ( ! sun c "o see :5 9 ! moon's umbra8 ,:5 9 its p5umbra8 ,h y ev] be5 9 ei!r8 ,:58 ,h y ev] be5 9 ! e>?'s umbra8 ,9 its p5umbra8 #d4 ,expla91 us+ a diagram1 ! =mation ( an inv]t$ image by a small ap]ture4 #e4 ,if ! sun is #de degrees above ! horizon1 :at is ! height ( a pole ca/+ a %ad[ #fj ft4 long8 #f4 ,if a %ad[ #f ft4 long is ca/ by a #aj-;ft4 pole /&+ v]tically ^u a walk1 h[ tall is ! tree ^: %ad[ is #db ft4 long1 bo? measurem5ts be+ made at ! same "t8 #g4 ,:y are ! %ad[s caus$ by an electric arc lamp s %>ply def9$8 #h4 ,:y %\ld s*oolroom w9d[s be all on "o side & rea* to ! ceil+8 #i4 ,:at is ! relation betwe5 ! size ( an image & its di/ance f ! ap]ture =m+ x8 ,c y prove ?is by geometry8 #aj4 ,:at are silh\ettes & h[ are !y produc$8 7#b7 ,,photometry ,,& ,,! ,,law ,,( ,,reflection #ceh4 ,photometry4--,x is desirable at times to comp>e ! int5sities ( illum9ation produc$ by light f diff]5t s\rces4 ,?is is done to det]m9e ! relative co/ or effectiv5ess ( v>i\s illum9ants su* z c&les1 k]os5e & gas lamps1 & electric lights ,! process ( det]m9+ ! relative int5sity ( lights or lamps is call$ photometry4 7,photos light47 ,! unit = measur+ ! p[] ( light is call$ a c&le p[]4 ,x is ! light produc$ by a sp]m c&le burn+ #abj gra9s p] h\r4 ,an ord9>y gas light burns #e or m cubic feet ( gas p] h\r & yields f #ae to #be c&le p[]4 ,a ,welsba* gas lamp1 consum+ #c cu4 ft4 p] h\r1 produces #ej to #ajj c&le p[]4 ,in/ead ( us+ c&les1 = practical photometry1 inc&esc5t lamps /&>diz$ by ! ,bureau ( ,/&>ds are us$ = te/+ or calibration purposes4 ,x is necess>y to di/+ui% betwe5 ! int5sity ( a lum9\s body1 i4e41 z a s\rce ( light1 & ! int5sity ( illum9ation ^u "s surface produc$ by a light4 ,x is consid]$ t two s\rces ( light are ( equal int5sity if !y produce equal illum9ation at equal di/ances4 #cei4 ,law ( ,int5sity ( ,light4--,a device = measur+ ! c&le p[] ( a light is call$ a photomet]4 ,its use is bas$ ^u ! law ( int5sity ( light4 ,! int5sity ( illum9ation ( a surface is inv]sely proportional to ! squ>e ( its di/ance f ! s\rce ( light4 ,?is relation is simil> to t exi/+ betwe5 ! int5sity ( a s\nd & ! di/ance f its s\rce4 ,! foll[+ device illu/rates ! tru? ( ?is law 9 a simple mann]4 ,illu/ration3 ,,fig4 #cej4--,! light spreads ov] f\r times ! area at twice ! di/ance4 ,cut a hole #a 94 squ>e 9 a l>ge %eet ( c>dbo>d 7,k7 & place ! c>d 9 an upright position #a met] f an arc light or o!r po9t s\rce ( light 7,l74 ,n[ rule in* squ>es ^u ano!r c>d 7,m7 & place x p>allel to ! fir/ c>d & #b met]s f x4 7,see ,fig4 #cej47 ,! light t pass$ ?r\gh ! hole ( #a sq4 94 at a di/ance ( #a met] is spread ov] #d sq4 94 at a di/ance ( #b met]s4 ,!re=e1 ! int5sity ( illum9ation on ea* squ>e in* ( ,m is "o-f\r? t ^u ! surface ( ,k4 ,if ,m is plac$ #c met]s f ! light1 #i sq4 94 are illum9at$1 or ! int5sity is "o-n9? t at #a met] di/ance4 ,illu/ration3 ,,fig4 #cea4--,! ,buns5 photomet]4 ,^! relations %[ t ! int5sity ( illum9ation is inv]sely proportional to ! squ>e ( ! di/ance f ! s\rce ( light4 ,an application ( ! law ( int5sity is made 9 us+ a simple 7,buns57 photomet]4 ,?is consi/s ( a c>d conta9+ a spot soak$ ) oil or melt$ wax4 7,see ,fig4 #cea47 ,! lights ^: int5sities are to be comp>$ are plac$ ^u opposite sides ( ! c>d4 ,! c>d is !n adju/$ s t ! spot appe>s ! same on bo? sides4 ,! illum9ation is n[ equal on bo? sides ( ! c>d & ! c&le p[]s ( ! two lights are proportional to ! squ>es ( _! di/ances f ! c>d4 ,! simple device j describ$ w give approximate results only4 ,= accurate results m elaborate app>atus is requir$4 #cfj4 ,measurem5t ( ! ,int5sity ( ,illum9ation4--,a /&>d c&le 7,art4 #ceh7 produces :5 light$ #a c&le p[]4 ,! illum9ation caus$ by ?is ^u a surface #a ft4 away & at "r angles to ! light rays is call$ a foot-c&le4 ,x is ! unit ( int5sity ( illum9ation4 ,a #d-;c&le-p[] lamp1 at a di/ance ( #a ft41 produces #d foot-c&les4 ,a #af-;c&le-p[] lamp at a di/ance ( #b ft4 also produces #d foot-c&les--7#af #b74 ,! int5sity ( illum9ation requir$ = a good light = see+ v>ies ) ! conditions4 ,?us1 = /age & /ore light+ ab\t #d foot-c&les are ne$$1 :ile homes & *ur*es may require b #a foot-c&le4 ,too great an int5sity ( illum9ation is z h>mful z n en\gh4 ,expos$ lights hav+ an int5sity ( m ?an #e c&le p[] p] squ>e in* are (t5 a cause ( eye tr\ble4 ,su* lights %\ld be protect$ by fro/$ globes4 ,a pleas+ =m ( light+ = l>ge halls & public build+s is ! indirect sy/em4 ,9 ?is1 ! lamps are hidd5 by reflectors :i* ?r[ ! light ^u ! ceil+ f :i* x is diffus$ ov] ! room4 ,?is =m ( light+ is m exp5sive ?an o!r sy/ems s9ce b a "p ( ! light is reflect$4 ,its co/ !re=e is an important factor :5 consid]+ its use4 #cfa4 ,! ,reflection ( ,light4--,! light reflect$ f ! surfaces ( bodies ab\t u gives u in=mation conc]n+ our surr\nd+s4 ,a k ( ! behavior ( light und]go+ reflection is n usually ga9$ f ord9>y obs]vation4 ,! law ( reflection ( light may be %[n1 h[ev]1 by an exp]im5t4 ,illu/ration3 ,,fig4 #ceb4--;,b is z f> back ( ! mirror z ,b is 9 front ( x4 ,illu/ration3 ,,*ri/ian ,,huyg5s 7,popul> ,sci5ce ,mon?ly7 ,*ri/ian ,huyg5s 7#afbi-afie74 ,dut* physici/2 inv5t$ ! p5dulum clock 7#afef72 develop$ ! wave !ory ( light2 discov]$ pol>ization ( light 7#afij74 ,illu/ration3 ,h4 ,v4 ,,helmholtz ,by ,p]mission ( ! ,b]l9 ,photographic ,co41 ,new ,york4 ,h]mann von ,helmholtz 7#ahba-ahid7 ,g]many4 ,e/abli%$ ! doctr9e ( cons]vation ( en]gy2 made _m discov]ies 9 s\nd2 inv5t$ ! oph?almoscope2 e/abli%$ ! physical basis ( tone quality4 ,a plane mirror1 ,m1 is held 9 a v]tical position re/+ ^u a %eet ( pap]4 7,see ,fig4 #ceb47 ,p9s are set upright 9 ! pap] at ,a & ,b4 ,on plac+ ! eye along ! l9e ,,ac & look+ t[>d ! mirror an image ( ,b may be se5 9 ! mirror due to ! light reflect$ f its surface4 ,p9s ,c & ,d are n[ set 9 ! pap] s t :5 "o looks along ! l9e ,,bd t[>d ! mirror "o may see all f\r p9s app>5tly 9 "o l9e4 ,?is indicates t ! light f ,a & ,c pass+ along ,,ca t[>d ,o is reflect$ back along ! light ,,cbd4 ,by means ( a rul]1 draw l9es ?r\gh ,,bd & ,,ac till !y int]sect at ,o4 ,also draw ,,po p]p5dicul> to ! mirror at ,o4 ,!n ! angles ,,aop & ,,bop w be f\nd equal4 ,^! are call$ ! angles ( incid5ce & reflection respectively4 ,! law ( reflection is !re=e /at$3 ,! angle ( reflection is equal to ! angle ( incid5ce4 ,^! angles are 9 ! same plane1 t ( ! pap]4 ,?is law applies 9 all cases ( reflection ( light4 ,x is simil> to ! law ( reflection ( s\nd 7,art4 #cbf47 ,important ,topics #a4 ,photometry1 law ( int5sity1 c&le p[]1 foot-c&le4 #b4 ,int5sity ( illum9ation4 #c4 ,reflect$ light & law ( reflection4 ,ex]cises #a4 ,bo? sides ( a c>d are equally illum9at$ :5 two lights are on opposite sides ( x & #aj & #cj cm4 respectively f x4 :at are _! relative int5sities8 #b4 ,:at are ! relative int5sities ( illum9ation f a gas light ^u a book #f ft4 & #b ft4 respectively f ! light8 #c4 ,:i* is m exp5sive p] c&le p[]8 ,h[ _m times z exp5sive8 ,a #ej-watt #af-;c&le-p[] inc&esc5t lamp at #aj c5ts p] kil[att-h\r or a #ajj-;c&le-p[] ,welsba* light burn+ #e cu4 ft4 ( gas p] h\r at #hj c5ts p] #ajjj cu4 ft4 ( gas4 7,f9d co/ ( ea* p] h\r1 & !n ! co/ ( #a c&le p[] h\r = ea*47 #d4 ,:y are n ord9>y %ad[s p]fectly d>k8 #e4 ,at :at di/ance w a #af-;c&le-p[] lamp give ! same illum9ation z a s+le c&le at #aj 948 #f4 ,if ! sun is at an elevation ( #cj degrees :at is ! angle ( incid5ce at :i* x /rikes ! surface ( wat]8 ,:at is ! angle betwe5 ! incid5t & ! reflect$ rays8 #g4 ,:at is ! diff]5ce betwe5 ! ph5om5a ( reflection ( light f a :ite %eet ( writ+ pap] & f a piece ( cle> w9d[ glass8 #h4 ,a horizontal ray ( light1 travel+ due ea/1 /rikes a v]tical mirror s t aft] reflection x is travel+ due nor?4 ,if ! mirror be n[ turn$ #aj degrees ab\t a v]tical axis1 ! nor? edge mov+ ea/1 :at w be ! direction ( ! reflect$ ray8 #i4 ,! necess>y illum9ation = read+ is ab\t #b foot-c&les4 ,h[ f> away may an #h-;c&le-p[] lamp be plac$8 #aj4 ,:at is ! illum9ation 9 foot-c&les ^u a surface #bj ft4 f an arc lamp hav+ an int5sity ( #ajjj c&le p[]8 #aa4 ,h[ f> f a #ajj-;c&le-p[] ,welsba* light w\ld ! illum9ation be #b foot-c&les8 7#c7 ,,mirrors ,,& ,,! ,,=mation ,,( ,,images ,illu/ration3 ,,fig4 #cec4--,reflection ( light1 7a7 diffus$1 7b7 regul>4 #cfb4 ,mirrors4--,! _m purposes s]v$ by mirrors 9 our e-day life has made _! use famili> to ev]yone4 ,yet )\t /udy & exp]im5t few und]/& _! prop]ties & action4 ,any smoo? surface may s]ve z a mirror1 z t ( glass1 wat]1 poli%$ wood1 or metal4 ,mo/ objects1 unlike mirrors1 h irregul> surfaces2 ^! scatt] or diffuse ! light t falls ^u !m4 7,see ,fig4 #cec;a47 ,?is is call$ diffus$ or irregul> reflection4 ,! reflection ( light f ! smoo? surface ( a mirror is regul>4 7,see ,fig4 #cec;b47 ,9 e case ( reflect$ light1 h[ev]1 ! angle ( reflection equals ! angle ( incid5ce1 diffusion be+ due to ! irregul>ity ( ! surface4 ,x is by means ( ! light diffus$ f ! surface ( illum9at$ bodies1 su* z plants1 animals1 food1 & manufactur$ articles1 t we see ! v>i\s objects ab\t u1 & x is ?is light t enables u to judge ( _! di/ance1 size1 =m1 color1 etc4 ,! moon is se5 by ! sunlight reflect$ f its surface4 ,moonlight is !re=e sunlight diffus$ by reflection4 ,! new moon is t phase or condition ( ! moon :5 only a n>r[ /rip ( ! moon's illum9at$ surface is turn$ t[>d ! e>?4 ,at ! "t ( ! full moon ! :ole illum9at$ surface is se54 #cfc4 ,images ,=m$ by a ,plane ,mirror4--,! mo/ common use ( mirrors is 9 ! =mation ( images4 ,! way 9 :i* images are =m$ by a plane mirror may be illu/rat$ by diagrams4 ,?us 9 ,fig4 #ced1 let ,l repres5t a lum9\s body & ,e & ,e two positions ( ! obs]v]'s eye4 ,take any l9e or ray z ,,lo along :i* ! light f ,l /rikes ! mirror ,o-,o4 ,x w be reflect$ s t angle ,,lop equals angle ,,poe4 ,simil>ly ) any o!r ray1 z ,,lo1 ! reflect$ ray ,o,e has a direction su* z t angle ,l,o,e equals angle ,p,o,e4 ,any o!r rays w be reflect$ 9 a simil> mann]1 ea* ( ! reflect$ rays appe>+ to ! eye to come f a po9t ,l beh9d ! mirror4 ,illu/ration3 ,,fig4 #ced4--,! virtual image ( a fix$ object z se5 9 a plane mirror1 has ! same location f e position ( ! obs]v]'s eye4 #cfd4 ,light ,waves & ,wave ,diagrams4--,j z a /ick cont9ually mov$ at ! surface ( a body ( wat] sets up a s]ies ( waves spread+ 9 all directions1 s "o may imag9e a tra9 ( waves s5t out by a lum9\s body ,l 7z 9 ,fig4 #cee7 to ! mirror ,,mn4 ,^! waves w be reflect$ f ! mirror z if ! s\rce ( light 7 at ,l4 ,x is mu* simpl] & m conv5i5t to locate ! position ( ! image ( a po9t by ! use ( l9es or rays 7z 9 ,fig4 #ced7 ?an by ! wave diagram 7z 9 ,fig4 #cee74 ,9 all ray diagrams1 h[ev]1 x %\ld be kept 9 m9d t ! s-call$ ray is a symbol us$ to repres5t ! direction tak5 by a "p ( a light wave4 ,?us 9 ,fig4 #ced1 ! light f ,l mov+ t[>d ,o is reflect$ to ,e along ! l9e ,,oe1 ! heavy l9es repres5t+ rays4 ,illu/ration3 ,,fig4 #cee4--,wave diagram ( image =m$ 9 a plane mirror4 #cfe4 ,to locate ! image ( an object =m$ by a plane mirror requires simply an application ( ! law ( reflection4 ,?us 9 ,fig4 #cef let ,,ab repres5t an object & ,,mn a plane mirror4 ,let ,,aa be a ray f ,a /rik+ ! mirror p]p5dicul>ly4 ,x is !re=e reflect$ back along ! same l9e t[>d ,a4 ,let ,,ao repres5t any o!r ray f ,a4 ,x w be reflect$ along ,,oe s t angle r equals i4 ,! int]section ( ,,ac & ,,oe at ,a beh9d ! mirror locates ! image ( ! po9t ,a1 z se5 by reflection f ! mirror4 ,! triangles ,,aco & ,a,,co may be prov$ equal by geometry4 ,!re=e ,a,c equals ,,ac4 ,?is indicates t ! image ( a po9t =m$ by a plane mirror is ! same di/ance back ( ! mirror z ! po9t itself is 9 front ( x4 ,?is pr9ciple may be us$ 9 locat+ ! image ( po9t ,b at ,b4 ,locat+ ! position ( ! end po9ts ( an image det]m9es ! position ( ! :ole image z ,a,b4 ,illu/ration3 ,,fig4 #cef4--,! image ,a,b is z f> back ( ! mirror ,m ,n z ! object ,a ,b is 9 front ( ! mirror4 #cff4 ,h[ ! ,image is ,se54--,suppose ! eye to be plac$ at ,e4 ,x w receive light f ,a by reflection z if x came f ,a4 ,simil>ly light />t+ f ,b rea*es ! eye f ! direction ( ,b4 ,!re is no?+ back ( ! mirror 9 reality t affects our sight1 ! light travel+ only 9 ! space 9 front ( ! mirror4 ,yet ! action ( ! reflect$ light is su* t x produces ! same effect z if x came f beh9d ! mirror4 ,images su* z are se5 9 plane mirrors are call$ virtual to di/+ui% !m f real images1 9 :i* light actually comes to ! eye f ! v>i\s p>ts ( ! visible image1 z f ! real image =m$ by a project+ lant]n ^u a scre51 or by an ap]ture z 9 ! p9-hole cam]a4 ,real images !re=e are ^? t c be obta9$ ^u a scre5 :ile virtual images _c4 #cfg4 ,multiple ,reflection4--,if ! light f an object is reflect$ by two or m mirrors v>i\s effects may be produc$1 z may be illu/rat$ by ! kaleidoscope4 ,?is consi/s ( ?ree plane mirrors s arrang$ t a cross-section ( ! ?ree =ms an equilat]al triangle4 ,! mirrors are plac$ 9 a tube across ! end ( :i* is a comp>tm5t ) a transluc5t cov] conta9+ pieces ( color$ glass4 ,on look+ ?r\gh ! tube1 ! reflections f ! sev]al surfaces produce beautiful hexagonal designs4 ,illu/ration3 ,,fig4 #ceg4--,p]spective view ( ,pepp]'s gho/4 ,illu/ration3 ,,fig4 #ceh4--;,diagram ( ! ,pepp] ,gho/ illusion4 #cfh4 ,optical ,illusions by a ,plane ,mirror4--,! illusion call$ ,pepp]'s ,gho/ is typical ( _m illusions produc$ by reflection4 ,x may be illu/rat$ by tak+ a piece ( plate glass1 ,m-,n1 a tumbl] ( wat]1 ,w1 & a light$ c&le1 ,c1 plac$ 9 a box1 ,b1 hav+ "o side op5 & arrang$ z %[n 9 p]spective 9 ,fig4 #ceg1 & 9 section 9 ,fig4 #ceh4 ,if ! effect is produc$ 9 a d>k5$ room1 ! obs]v] at ,e sees a virtual image ( ! light$ c&le z if x 7 9 ! glass ( wat]1 ! wat] be+ se5 by transmitt$ light ?r\gh ! plate glass1 ! latt] =m+ a virtual image ( ! c&le by reflection4 ,"s ( ! illusions produc$ by ?is means are3 7a7 ! figure susp5d$ 9 mid air2 7b7 ! bu/ ( a p]son )\t a trunk2 7c7 ! /age gho/2 7d7 ! disappe>+ b\quet4 ,illu/ration3 ,,fig4 #cei4--;,action ( a concave mirror on p>allel rays ( light4 ,illu/ration3 ,,fig4 #cfj4--,real image =m$ by a concave mirror4 #cfi4 ,concave ,mirrors4--,ano!r useful piece ( physical app>atus is ! concave sph]ical mirror4 ,x is frequ5tly made f plano-convex l5ses by silv]+ ! convex surface ( ! l5s1 ?us mak+ a concave reflect+ surface f ! inn] surface ( ! silv]$ "p2 !y are also made by poli%+ ! inn] surfaces ( metallic sph]ical %ells4 ,! concave mirror is repres5t$ 9 section 9 ,fig4 #cei by ! curve ,,mn2 ,c is ! c5t] ( curvature or ! c5t] ( ! surface ( :i* ?is mirror ,,mn is a "p2 ! l9e ,,vc ?r\gh ! c5t] ,v ( ! mirror is call$ ! pr9cipal axis2 :ile any o!r l9e pass+ ?r\gh ,c is call$ a second>y axis4 ,! po9t midway betwe5 ! v]tex ,v & c5t] ( curvature ,c is call$ ! pr9cipal focus1 ,f4 ,x is ! po9t ?r\gh :i* p>allel incid5t rays pass aft] reflection4 ,! angle ,,mcn :i* ! curve ( ! mirror subt5ds at ! c5t] is call$ ! ap]ture ( ! mirror4 ,we le>n$ 9 ,art4 #cfa1 ! angle ( reflection ( a ray ( light is always equal to ! angle ( incid5ce no matt] :at ! nature ( ! reflect+ surface may be4 ,if ! reflect+ surface is a regul> concave surface1 l ! inn] surface ( a sph]e1 ! rays ( light com+ f a po9t s\rce may aft] reflection come to a focus1 =m+ a real image4 ,! two extreme po9ts ( an object %\ld be select$ = locat+ its image2 ,fig4 #cfj %[s ! con/ruction4 ,! real images =m$ by concave mirrors are always inv]t$4 ,! pr9cipal focus ( a concave mirror may be obs]v$ by hold+ ! mirror 9 a beam ( sunlight ent]+ a d>k5$ room4 ,! sun's rays aft] reflection conv]ge to =m a small1 r\nd1 int5se spot ( light1 :i* is a real image ( ! sun1 locat$ at ! pr9cipal focus ( ! mirror4 ,! di/ance ( ! pr9cipal focus f ! mirror is ! lea/ di/ance t a real image c be =m$ 9 front ( a concave mirror4 #cgj4 ,virtual ,images by ,concave ,mirrors4--,:5 light comes f a small po9t situat$ betwe5 a concave mirror & its pr9cipal focus1 ! reflect$ rays are div]g5t & h5ce no real image ( ! object c be f\nd 9 front ( ! mirror4 ,b if ! rays are ext5d$ beh9d ! mirror !y w meet 9 a po9t call$ ! virtual focus4 ,?is is ! po9t f :i* !y appe> to come4 ,any image ( an object situat$ betwe5 ! pr9cipal focus & a concave mirror is !re=e a virtual image1 erect & l>g] ?an ! object4 7,see ,fig4 #cfa47 ,illu/ration3 ,,fig4 #cfa4--,virtual image =m$ by a concave mirror4 #cga4 ,con/ruction ( ,real ,images4--,!re are five positions at :i* an object may be situat$ 9 front ( a concave mirror1 namely3 7#a7 beyond ,c2 7#b7 at ,c2 7#c7 betwe5 ,c & ,f2 7#d7 at ,f & 7#e7 betwe5 ,f & ,v4 ,!re are two ways by means ( :i* ! image =m$ at ea* ( ^! positions may be locat$1 namely2 7#a7 exp]im5tally1 by all[+ ! rays ( light f a lum9\s body to focus on a scre5 & 7#b7 diagrammatically4 ,by ! latt] me?od ! two rays ( light are consid]$ ! c\rse ( ea* ( :i* may easily be det]m9$2 fir/1 ! ray :i* /rikes ! mirror p>allel to its pr9cipal axis & :i* aft] reflection passes ?r\gh ! pr9cipal focus2 second1 ! ray :i* pass+ ?r\gh ! c5t] ( curvature /rikes ! mirror at "r angles & !re=e aft] reflection mu/ pass directly back along its incid5t pa?4 ,:]e ^! two reflect$ rays int]sect is locat$ ! real image ( ! object4 ,:5ev] ^! two rays ( light d actually int]sect1 z 9 ,fig4 #cfj1 a real image 7ab7 is =m$ ( ! object ,,ab4 ,! po9ts ,a & a1 ,b & b & o!rs simil>ly situat$ on an axis ext5d+ ?r\gh ! c5t] ( curvature ,c are call$ conjugate foci1 = !y are s relat$ t an object be+ at ei!r "o1 its image w be f\nd at ! o!r4 ,illu/ration3 ,,fig4 #cfb4--;,action ( a convex mirror ^u p>allel rays ( light4 #cgb4 ,! ,convex ,mirror4--,!re are few practical uses to :i* convex mirrors c be put4 ,!y are sometimes us$ to give ! *auffeur ( an automobile a view ( ! road beh9d him4 ,x is !n atta*$ to ! w9d %ield by a %ort rod4 ,! reflect$ rays com+ f a ,convex mirror are always div]g5t 7see ,fig4 #cfb71 h5ce ! image is always virtual & locat$ beh9d ! reflect+ surface4 ,! me?od ( con/ruction = images =m$ by a convex mirror is simil> to t = concave mirrors4 7,see ,fig4 #cfc47 ,! c5t] ( curvature & pr9cipal focus are beh9d ! mirror & consequ5tly ! reflect$ rays h to be produc$ backw>d until !y meet4 ,! images are always virtual1 erect & small] ?an ! object4 ,illu/ration3 ,,fig4 #cfc4--;,con/ruction ( an image by a convex mirror4 ,illu/ration3 ,,fig #cfd4--;,illu/rations ( ,sph]ical ,ab]ration4 #cgc4 ,sph]ical ,ab]ration4 ,sometimes 9 a concave mirror :5 ! ap]ture ,,mcn 7,fig4 #cfd7 is l>ge ! images are blurr$ or indi/9ct4 ,?is is due to ! fact t ! incid5t rays ne> ! out] edge ( ! mirror d n focus aft] reflection at ! same po9t z ^? :i* pass into ! mirror ne> ! v]tex1 b cross ! pr9cipal axis at po9ts betwe5 ! mirror & pr9cipal focus z is %[n 9 ,fig4 #cfd2 ?is result is call$ sph]ical ab]ration4 ,! l>g] ! ap]ture ( ! mirror ! m ! image is blurr$4 ,concave mirrors 9 practical use d n h an ap]ture mu* great] ?an #aj degrees4 ,?is non-focus+ ( ! rays ( light by curv$ reflect+ surfaces may be notic$ 9 _m places1 z :5 light is reflect$ f ! inside ( a cup t conta9s milk or f ! inside ( a wide gold r+ plac$ on top ( a piece ( :ite pap]4 ,! pupil w note o!r in/ances4 ,?is curve ( light obs]v$ is call$ ! cau/ic by reflection4 #cgd4 ,p>abolic ,mirrors4--,! be/ possible surface to give to concave mirrors is p>abolic4 ,?is is a curve :i* may be g5]at$ by mov+ a po9t s t its di/ance f a fix$ po9t & a fix$ l9e are always equal4 ,if a s\rce ( light is plac$ at ,f ! rays aft] reflection are r5d]$ p>allel4 ,see ,fig4 #cfe4 ,?is reflector is us$ 9 automobile lamps1 headlights ( locomotives1 se>*-lights1 etc4 ,x is also us$ 9 l>ge reflect+ a/ronomical telescopes to collect z l>ge an am\nt ( light z possible f di/ant />s & br+ x to a focus4 ,su* mirrors may be made exce$+ly accurate4 ,illu/ration3 ,,fig4 #cfe4--,p>abolic mirror4 ,important ,topics #a4 ,reflection3 regul>1 diffus$2 plane mirrors2 laws ( reflection4 #b4 ,=mation & location ( images by plane mirrors4 ,wave & ray diagrams4 #c4 ,multiple reflection1 illusions4 #d4 ,curv$ mirrors1 uses2 concave1 convex1 p>abolic4 ,ex]cises #a4 ,di/+ui% betwe5 regul> & diffus$ reflection4 ,by means ( :i* d we see non-lum9\s bodies8 #b4 ,c\ld a p]fect reflect+ surface be se58 ,expla94 #c4 ,a p5cil is /ood upright 9 front ( a plane mirror set at an angle ( #de degrees to ! v]tical4 ,%[n by a diagram ! location & position ( ! image4 #d4 ,%[ by diagrams ! position & location ( ! images ( a p5cil 7a7 :5 /&+ erect & 9 front ( a v]tical mirror4 7b7 :5 /&+ ^u a horizontal mirror4 #e4 ,:at is ! diff]5ce betwe5 a real & a virtual image8 #f4 ,a /&>d c&le & a lamp give equal illum9ations to a scre5 t is #a ft4 f ! c&le & #f ft4 f ! lamp4 ,:at is ! c&le p[] ( ! lamp8 ,expla94 #g4 ,:y are walls f9i%$ 9 r\gh pla/] or pa9t$ ) s(t tones )\t gloss bett] = s*oolrooms ?an glossy pa9ts or smoo? :ite pla/]8 #h4 ,try to read a pr9t$ page by look+ at its image 9 a mirror4 write y\r "n backw>d on a %eet ( pap]1 & !n look at ! image ( ! writ+ 9 a mirror4 ,:at effect is produc$ by ! mirror 9 ea* case8 #i4 ,if ! po9t ( a p5cil is held to ! surface ( a piece ( plate-glass mirror two or m images may be se5 9 ! mirror4 ,expla94 #aj4 ,giv5 a small light$ c&le1 a concave mirror1 a met] /ick1 & a :ite scre51 h[ w\ld y prove ! /atem5ts made 9 ,arts4 #cfi & #cgj conc]n+ ! location ( images =m$ by concave mirrors8 ,make ! diagram 9 ea* case4 #aa4 ,:y d images se5 9 a quiet pond ( wat] appe> inv]t$8 ,expla9 by a diagram4 7#d7 ,,refraction ,,( ,,light #cge4 ,common ,examples ( ,refraction4--,ev]yone has notic$ ! app>5t b5d+ ( an o>1 ( a /ick1 or ( a spoon :5 plac$ 9 wat] 7see ,fig4 #cff71 :ile _m h obs]v$ t ! bottom ( a pond or /ream looks ne>] to ! surface ?an x really is4 ,^! & simil> illusions are due to ! refraction or b5d+ ( light rays z !y pass f "o m$ium to ano!r4 ,! pr9ciples ( refraction are among ! mo/ useful f\nd 9 ! /udy ( light s9ce application is made ( !m 9 ! con/ruction & use ( important optical in/rum5ts1 su* z ! cam]a1 microscope1 telescope1 & ! eye4 ,illu/ration3 ,,fig4 #cff4--,! /ick appe>s to be b5t on acc\nt ( refraction4 #cgf4 ,action ( ,light ,und]go+ ,refraction4--,if a beam ( sunlight be admitt$ to a d>k5$ room & reflect$ by a mirror s t x /rikes ! surface ( wat] 9 a glass j>1 a "p ( ! beam may be se5 to be reflect$ :ile ano!r portion is transmitt$ ?r\gh ! wat] 7,fig4 #cfg74 ,! reflect$ beam foll[s ! law ( reflection :ile ! transmitt$ beam is se5 to be refract$1 or to h its c\rses slightly *ang$ 9 direction ^u ent]+ ! wat]4 ,if ! mirror is turn$ s t ! angle at :i* ! light /rikes ! wat] is *ang$1 ! am\nt ( refraction or *ange ( c\rse ( ! light is v>i$4 ,:5 ! light /rikes ! wat] p]p5dicul>ly !re is no refraction4 ,on ! o!r h&1 ! great] ! angle at :i* ! light /rikes ! wat] ! great] ! b5d+4 ,illu/ration3 ,,fig4 #cfg4--,"p ( ! ray is reflect$ & "p passes into ! wat] & is refract$4 ,illu/ration3 ,,fig4 #cfh4--;,illu/rat+ ! laws ( refraction ( light4 #cgg4 ,laws ( ,refraction4 ,! action ( light on ent]+1 pass+ ?r\gh1 & leav+ a great v>iety ( sub/ances has be5 c>efully /udi$4 ,a summ>y ( ! results ( ^! obs]vations is giv5 9 ! foll[+ laws ( refraction3 ,i4 ,:5 light ent]s a transp>5t body1 p]p5dicul>ly1 x passes on )\t *ang+ its direction4 ,,ii4 ,:5 light ent]s a d5s] transp>5t body obliquely1 x is b5t t[>d ! p]p5dicul>2 :5 light ent]s a less d5se body obliquely1 x is b5t away f ! p]p5dicul>4 7,see ,fig4 #cfh47 #cgh4 ,! cause ( refraction may be illu/rat$ by consid]+ a l9e ( m5 mov+ across a field & occupy+ at equal "t int]vals ! successive positions #a1 #b1 #c1 etc41 indicat$ 9 ,fig4 #cfi4 ,suppose t ! upp] & l[] p>ts ( ! field h a smoo? h>d surface1 :ile at ! c5t] is a /rip ( newly pl\gh$ gr\nd4 ,! l9e w move m sl[ly ov] ! pl\gh$ field ?an ov] ! h>d field4 ,?is w result 9 a ret>dation ( ! end ( ! l9e fir/ /rik+ ! s(t gr\nd ) a result+ *ange ( direction ( ! l9e1 t[>d ! p]p5dicul> to ! edge ( ! field 7on ent]+ ! place ( m difficult travel71 & away f ! p]p5dicul> on mov+ into a place :]e increas$ spe$ results4 ,illu/ration3 ,,fig4 #cfi4--;,diagram illu/rat+ ! cause ( refraction4 #cgi4 ,index ( ,refraction4--,by /udy+ ! *ange ( direction ( ! m>*+ m5 z %[n 9 ,fig4 #cfi x is evid5t fir/ t x is due to a diff]5ce 9 spe$ 9 ! two m$ia4 ,x is n easy to measure ! spe$ ( light 9 a m$ium4 ,h[ev]1 ! am\nt ( refraction may be det]m9$ easily & f ?is ! relative spe$ may be comput$4 ,! numb] t expresses ! ratio ( ! spe$ ( light 9 air to its spe$ 9 ano!r m$ium is call$ ! index ( refraction ( t m$ium4 ,! relative spe$s ( light1 or ! indices ( refraction = "s sub/ances1 are3 wat]1 #a4cc1 cr[n glass1 #a4ea1 fl9t glass1 #a4fa1 diamond1 #b4dg1 c>bon bisulphide1 #a4fd4 ,illu/ration3 ,,fig4 #cgj4--,! incid5t ray & ! em]g5t rays are p>allel4 #chj4 ,plates1 ,prisms1 ,l5ses4--,! refraction ( light is usually obs]v$ :5 x is pass+ ?r\gh a plate1 a prism1 or a l5s4 ,! important diff]5ces betwe5 ! effects ( ea* 9 refract+ light are illu/rat$ 9 ,figs4 #cgj1 #cga & #cgb4 ,9 ,fig4 #cgj x is se5 t ! refraction ( ! ray on ent]+ ! glass is c\nt]act$ by ! refraction away f ! p]p5dicul> ^u leav+ x4 ,s t ! ent]+ & em]g5t rays are p>allel4 ,9 ,fig4 #cga ! refraction at ! two surfaces ( ! prism results 9 a *ange ( direction ( ! ray1 ! c\rse be+ b5t t[>d ! ?ick] "p ( ! prism4 ,9 ,fig4 #cgb x may be notic$ t ! convex l5s resembles two prisms ) _! bases toge!r4 ,s9ce all p>ts ( ! l5s refract light t[>d ! ?ick] "p1 ! c5t]1 ! effect ( ! convex l5s is to br+ ! rays ( light to a focus1 at ,f4 ,illu/ration3 ,,fig4 #cga4--;,effect ( a prism ^u a ray ( light4 ,illu/ration3 ,,fig4 #cgb4--,! convex l5s br+s ! rays ( light to a focus4 #cha4 ,total ,reflection4--,x has be5 %[n t :5 light passes f a d5s] to a light] m$ium1 z f glass or wat] to air1 t ! beam is refract$ away f ! p]p5dicul>4 ,?is is illu/rat$ 9 ,fig4 #cgc4 ,! diagram repres5ts ! *ange 9 ! c\rse ( a ray ( light t passes ?r\gh wat] to a surface ) air above x4 ,a ray /rik+ p]p5dicul>ly passes ?r\gh )\t refraction4 ,o!r rays %[ increas+ refraction ) increas+ angle ( incid5ce4 ,= "o ray ! angle ( refraction is s l>ge t ! refract$ ray is p>allel to ! surface4 ,:5 ?is condition is rea*$1 ! angle ( incid5ce is call$ ! critical angle4 ,any increase 9 ! angle ( incid5ce causes all ( ! light to be reflect$ z is ! beam ,e4 ,?is action is call$ total reflection1 ! c\rse ( ! reflect$ ray be+ accord+ to ! law ( reflection4 ,a "r-angle prism 7see ,fig4 #cgd7 is (t5 us$ :]e a mirror w\ld ord9>ily be employ$1 ! total reflection occurr+ )9 ! prism giv+ m satisfactory results ?an a mirror4 ,see ,art4 #cih = a description ( ! ,zeiss b9ocul> field-glass = an example ( ?is use ( total reflection4 ,illu/ration3 ,,fig4 #cgc4--;,an example ( total reflection4 ,illu/ration3 ,,fig4 #cgd4--,total reflection 9 a "r-angle prism4 ,! mirage 7see ,fig4 #cge7 is an optical illusion by :i* di/ant objects1 bel[ ! horizon1 are sometimes pla9ly se54 ,?is ph5om5on is mo/ frequ5tly obs]v$ 9 hot1 des]t regions1 :5 ! air conditions are su* t ! l[] /rata ne> ! gr\nd are v mu* hott] ?an ^? above4 ,^! l[] /rata1 hav+ exp&$ ! mo/1 are less d5se ?an ! cool] ones above4 ,h5ce a ray ( light travel+ obliquely d[nw>d is refract$ m & m until total reflection takes place4 ,! images se5 are inv]t$ giv+ a repres5tation ( trees or o!r objects reflect$ on ! surface ( /ill wat]4 ,! mirage is also frequ5tly se5 at sea1 %ips be+ obs]v$1 sometimes erect1 sometimes inv]t$1 app>5tly sail+ 9 ! cl\ds ne> ! horizon4 ,ov] ! ,great ,lakes1 trees1 boats1 & t[ns on ! opposite %ore1 sixty or sev5ty miles away1 c sometimes be pla9ly se51 app>5tly b a few miles out4 ,9 ?is case ! images are erect1 ! total reflection be+ f w>m1 /ill lay]s ( air ov] cold] lay]s ne> ! wat]4 ,illu/ration3 ,,fig4 #cge4--;,diagram ( a mirage4 ,important ,topics 7,a7 ,refraction3 cause1 illu/ration1 two pr9ciples4 7,b7 ,index ( refraction1 mean+4 7,c7 ,plates1 prisms1 l5ses1 action ( ea*4 7,d7 ,total reflection1 uses4 ,ex]cises #a4 ,compute ! spe$ ( light 9 wat]1 ! index ( refraction be+ #a4cc4 #b4 ,if "o wi%$ to %oot a fi% "u wat]1 %\ld he aim at ! app>5t location ( ! fi% z view$ f ! air8 ,expla91 us+ a diagram4 #c4 ,def9e refraction4 ,m5tion two illu/rations ( ?is action t y h obs]v$ out ( s*ool4 #d4 ,:y does ! moon look l>g] ne> ! horizon8 #e4 ,is y\r reflection se5 9 a pool ( wat] upside d[n8 ,:y8 #f4 ,:y does x :it5 molasses c&y to pull x8 #g4 ,:5 look+ at a build+ ?r\gh ! ord9>y glass ( a w9d[ :y d /raight l9es ( ! build+ appe> to be s di/ort$8 ,:at makes !m appe> to move z y move y\r head slightly8 #h4 ,expla9 ! ph5om5on :i* "o obs]ves :5 look+ at an object ?r\gh ! air aris+ f a hot /ove or radiator4 #i4 ,frequ5tly ! horizontal diamet] ( ! sett+ sun appe>s to be great] ?an ! v]tical4 ,expla94 #aj4 ,expla9 :y "o obs]ves sev]al images ( a lum9\s body l a light$ c&le :5 ! reflect$ light f a ?ick glass mirror ent]s ! eye1 ! angle ( reflection be+ l>ge4 7#e7 ,,! ,,=mation ,,( ,,images ,,by ,,l5ses #chb4 ,uses ( ,l5ses 9 ,optical ,in/rum5ts4--,! use ( in/rum5ts t employ l5ses 9 _! op]ation1 su* z spectacles1 read+ & op]a glasses1 & ! cam]a1 microscope1 & telescope1 is famili> to mo/ /ud5ts ( physics4 ,! "p play$ by ! l5ses1 h[ev]1 is n g5]ally und]/ood4 ,consequ5tly ! /udy ( ! =mation ( images by l5ses is ( g5]al int]e/ & importance4 #chc4 ,=ms ( ,l5ses4--,:ile a l5s may be =m$ f any transp>5t solid x is commonly made ( glass4 ,x may h two curv$ surfaces or "o curv$ & "o plane surface4 ,mo/ l5ses are sph]ical l5ses1 s9ce _! curv$ surfaces =m a "p ( ! surface ( a sph]e4 ,fig4 #cgf repres5ts a sph]ical l5s ) a curv$ surface co9cid+ ) t ( a sph]e ^: c5t] is at ,c4 ,?is c5t] is call$ ! c5t] ( curvature1 :ile ! radius ( ! sph]e ,r1 is ! radius ( curvature4 ,illu/ration3 ,,fig4 #cgf4--;,=mation ( a sph]ical l5s4 ,!re are two classes ( l5ses3 ^? ?ick 9 ! middle are call$ convex1 :ile ^? ?ick at ! edges are concave4 ,! mode ( con/ruct+ ! six =ms ( sph]ical l5ses is %[n 9 ,fig4 #cgg4 ,^! are nam$ z foll[s3 7#a7 d\ble convex1 7#b7 plano convex1 7#c7 concavo-convex1 7#d7 d\ble concave1 7#e7 plano concave1 7#f7 convexo-concave4 ,illu/ration3 ,,fig4 #cgg4--;,=ms ( ,l5ses4 #a4 d\ble convex2 #b4 plano convex2 #c4 concavo convex2 #d4 d\ble concave2 #e4 plano concave2 #f4 convexo concave4 ,illu/ration3 ,,fig4 #cgh4--,! action ( a burn+ glass4 #chd4 ,effect ( ,l5ses ^u ,light4--,! mo/ important *>act]i/ic ( a l5s is its effect ^u a beam ( light4 ,mo/ p]sons h se5 a burn+ glass1 a d\ble convex l5s1 us$ to br+ to a po9t1 or focus1 a beam ( sunlight4 ,to %[ ! action ( a burn+ glass s5d a beam ( light into a d>k5$ room1 & place 9 its pa? a d\ble convex l5s4 7,see ,fig4 #cgh47 ,if two blackbo>d eras]s are /ruck toge!r ne> ! l5s1 ! *alk p>ticles 9 ! pa? ( ! light are /rongly illum9at$1 %[+ t ! light aft] pass+ ?r\gh ! l5s x br\ght to a focus & t x spreads out beyond ?is po9t4 ,?is po9t to :i* ! cone ( light rays conv]ges aft] pass+ ?r\gh ! convex l5s is call$ ! pr9cipal focus ( ! l5s4 ,! di/ance f ! pr9cipal focus to ! c5t] ( ! l5s is ! focal l5g? or pr9cipal focal di/ance ( ! l5s4 ,! focal l5g? ( d\ble convex l5ses ( cr[n glass is ab\t ! same z ! radius ( curvature ( ei!r surface4 ,! action ( a convex or conv]g+ l5s ^u light may be bett] und]/ood by /udy+ ,fig4 #cgi 9 :i* light is pass+ f ,s to ,f4 ,! successive positions & %ape ( ! advanc+ light waves are indicat$ by l9es drawn across ! beam4 ,! light be+ ret>d$ m 9 ! ?ick] "p ( ! l5s1 ! light waves on leav+ ! l5s h a concave front4 ,s9ce light waves t5d to move at "r angles to ! front ( ! wave1 ! light is br\ght to a focus4 ,aft] pass+ ! focus ! waves h a convex front1 =m+ a div]g+ cone4 ,illu/ration3 ,,fig4 #cgi4--,wave diagram ( light pass+ ?r\gh a convex l5s4 #che4 ,concave ,l5ses4--,:5 sunlight passes ?r\gh a concave l5s a div]g+ cone ( light is =m$4 7,see ,fig4 #chj47 ,?is is caus$ by ! edges ( ! wave be+ ret>d$ m ?an ! c5t]1 produc+ a convex wave front4 ,?is div]g+ cone ( light acts z if x _h proce$$ f a lum9\s po9t at ,f4 ,?is po9t is call$ a virtual focus & is ne>ly at ! c5t] ( ! curvature ( ! ne>] surface4 ,illu/ration3 ,,fig4 #chj4--,wave diagram ( light pass+ ?r\gh a concave l5s4 #chf4 ,! ,=mation ( ,images by ,l5ses4--,if a beam compos$ ( p>allel rays ( light1 z sunlight1 is s5t 9 turn ?r\gh ?ree convex l5ses ( ! same diamet] b ( diff]5t ?ickness1 x is f\nd t ! ?ick] ! l5s ! great] is its conv]g+ p[]1 or ! %ort] is its focal l5g?4 7,see ,fig4 #cha47 ,n[ if a lum9\s body1 su* z a light$ c&le1 be plac$ ne> ! convex l5s b beyond its focal l5g?1 ! light w be br\ght to a focus ^u ! o!r side ( ! l5s & an image ( ! c&le may be cle>ly se5 ^u ! scre5 plac$ at ?is po9t4 7,see ,fig4 #chb47 ,! two po9ts s situat$ on opposite sides ( a l5s t an object at "o w =m an image at ! o!r are call$ conjugate foci4 ,illu/ration3 ,,fig4 #cha4--,! ?ick] ! l5s1 ! %ort] is its focal l5g?4 ,illu/ration3 ,,fig4 #chb4--;,c & ,s are at conjugate foci4 ,x w be helpful to comp>e ! images =m$ ( a c&le by an ap]ture & by a convex l5s4 ,rays ( light f ea* po9t ( ! lum9\s body pass ?r\gh ! ap]ture 9 /raight l9es & produce ^u ! scre5 a light$ space ( ! same %ape z ! c&le4 ,?is image is r hazy 9 outl9e4 ,ea* cone ( rays f lum9\s po9ts ( ! flame is br\ght by ! l5s to a focus on ! scre51 produc+ a %>p image4 ,x is ! conv]g+ p[] ( convex l5ses t enables !m to produce cle> images4 ,illu/ration3 ,,fig4 #chc4--;,con/ruction ( a real image by a convex l5s4 #chg4 ,! ,con/ruction ( ,diagrams to ,repres5t ! ,=mation ( ,images by ,l5ses4--,j z ! e>? has an axis at "r angles to its equator to :i* are ref]r$ positions & di/ances1 s a l5s has a pr9cipal axis at "r angles to its greate/ diamet] & along ?is axis are c]ta9 def9ite positions z %[n 9 ,fig4 #chc4 ,let ,,mn be ! pr9cipal axis ( a convex l5s1 ,p & ,p are pr9cipal foci on ei!r side ( ! l5s1 ,s & ,s are second>y foci4 ,^! are at po9ts on ! pr9cipal axis t are twice z f> f ,o1 ! c5t] ( ! l5s1 z are ! pr9cipal foci4 ,9 ! =mation ( images by a convex l5s1 sev]al di/9ct cases may be notic$3 7,a7 ,if a lum9\s body is at a great di/ance at ! left1 its light is br\ght to a focus at ,p1 or its image is =m$ at ,p4 7,b7 ,z ! object approa*es ! l5s ! image gradually rec$es until ! object & image are at ,s & ,s1 equally di/ant f ,o & ( equal size 7z 9 ,fig4 #chc74 ,! object & image are n[ said to be at ! second>y foci ( ! l5s4 7,c7 ,z ! object moves f ,s to ,p ! image rec$es1 rapidly increas+ 9 size until 7,d7 :5 ! object is at ,p ! rays become p>allel & no image is =m$4 7,e7 ,:5 ! object is betwe5 ,p & ! l5s1 ! rays appe> to proce$ f po9ts back ( ! object1 ?us =m+ an erect1 l>g]1 virtual image ( ! object4 7,see ,fig4 #chd47 ,?is la/ arrangem5t illu/rates ! simple microscope4 ,) a concave l5s b "o case is possible1 t correspond+ to ! "o la/ m5tion$ ) convex l5ses2 s9ce ! rays f a body are div]g5t aft] pass+ ?r\gh a concave l5s !y appe> to proce$ f po9ts ne>] ! l5s ?an ! object & h5ce a virtual1 erect1 small] image ( ! object is =m$4 ,?is virtual image may be se5 by look+ ?r\gh ! l5s t[>d ! object4 7,see ,fig4 #che47 ,illu/ration3 ,,fig4 #chd4--;,con/ruction ( a virtual image by a convex l5s4 ,illu/ration3 ,,fig4 #che4--;,con/ruction ( a virtual image by a concave l5s4 #chh4 ,! ,l5s ,equation4--,! location ( ei!r ! object or ( ! image ^u ! pr9cipal axis ( ! l5s may be calculat$ if ! position ( "o ( ^! & ! focal l5g? are kn[n4 ,?is is accompli%$ by ! use ( a =mula #a_/;,f #a_/;,d#j #a_/;,d#a 9 :i* ,f repres5ts ! focal l5g? & ,d#j & ,d#a ! di/ance f ! l5s ( ! object & ! image respectively4 ,?us if an object is plac$ #cj cm4 f a l5s ( #aj cm4 focal l5g?1 :]e w ! image be =m$8 ,?us3 #a_/aj #a_/cj #a_/;,d & #c;,d#a ,d#a #cj1 or #b;,d#a #cj ,d#a #ae4 ,?is result indicates t a real image w be #ae cm4 f ! l5s4 ,a m9us value w\ld indicate a virtual image4 ,important ,topics 7,a7 ,l5ses3 convex1 concave1 six =ms1 c5t] & radius ( curvature4 7,b7 ,pr9cipal focus1 focal l5g?1 virtual focus1 conjugate foci4 7,c7 ,pr9cipal axis1 images =m$ :5 object is 9 v>i\s locations4 7,d7 ,computation ( location ( images4 ,ex]cises #a4 ,:y is an image ( a c&le =m$ by an ap]ture1 n %>ply def9$8 #b4 ,:5 a photograph] takes y\r picture & moves ! cam]a ne>] y1 mu/ he move ! gr\nd glass scre5 t[>d ! l5s or away f x8 ,expla94 #c4 ,h[ c y f9d ! pr9cipal focal l5g? ( a l5s4 #d4 ,h[ c y te/ a spectacle l5s to see :e!r x is convex concave8 #e4 ,:5 w a convex l5s produce a virtual image8 ,h y ev] se5 "o8 ,:]e8 #f4 ,:5 a photograph] wi%es to obta9 a full l5g? view ( a p]son1 :]e does he place ! cam]a8 #g4 ,! focal l5g? ( ! l5s is #bd cm4 ,h[ f> f ! l5s mu/ an object be plac$ 9 ord] t a real image may be ?ree times z long z ! object8 #h4 ,!re is a p]fect image ( an object on ! gr\nd glass ( a cam]a4 ,! c5t] ( ! l5s is #bj cm4 9 front ( ! image & ! object #ge cm4 f ! l5s4 ,:at is ! focal l5g? ( ! l5s8 #i4 ,an object is #fj cm4 f ! l5s1 ! image #abj cm4 f x4 ,f9d ! focal l5g?4 #aj4 ,h[ c y f9d exp]im5tally ! pr9cipal focal l5g? ( a l5s8 #aa4 ,a l5s is us$ to project an enl>g$ image ( a c&le ^u a scre54 ,:i* is f>!r f ! l5s1 ! c&le or ! image8 ,expla94 7#f7 ,,optical ,,in/rum5ts #chi4 ,! ,eye4--,! mo/ common optical in/rum5t is ! eye4 ,:ile ! /ructure ( ! eye is complicat$1 ! pr9ciple ( x is simple1 involv+ ! =mation ( an image by a d\ble convex l5s4 7,see ,fig4 #chf1 9 :i* is %[n a front to back1 v]tical cross-section ( ! eye47 ,! eye appe>s to be made ( portions ( two sph]es1 "o ( :i*1 small] ?an ! o!r1 is plac$ 9 front4 ,?is project+ "p is transp>5t1 b refracts ! light :i* /rikes x obliquely1 s z to turn x into ! eye4 ,?is enables u to see objects at ! side :5 look+ /raight ahead4 ,te/ ?is by look+ directly 9 front ( y & see h[ f> back on ea* side ( ! head y c notice a movem5t ( ! =ef+] ( ea* h&4 ,illu/ration3 ,,fig4 #chf4--;,cross-section ( ! eye4 #cij4 ,action ( ! ,eye 9 ,vision4--,:5 we look at an object1 a small1 real1 inv]t$ image is =m$ ^u ! ret9a at ! back ( ! int]ior ( ! eye4 ,! ret9a is an expansion ( ! optic n]ve & cov]s ! inn] surface at ! back ( ! eyeball4 ,see+ is due to ! action ( light 9 =m+ images ^u ! ret9a4 ,our eyes are s con/ruct$ t :5 !y are relax$ ! l5s is adju/$ to =m cle> images ( di/ant objects ^u ! ret9a4 ,if we look f di/ant to ne> objects )\t *ang+ ! %ape ( ! eye l5s1 a %>p image ( ! latt] _c be =m$ & we get a blurr$ impression4 ,x is difficult1 h[ev]1 to look at objects )\t automatically adju/+ ! eye l5s s t x w make a %>p image4 ,te/ ?is by look+ out ( a w9d[ at a di/ant object1 !n )\t mov+ ! head or eyes look at ! glass ( ! w9d[2 y w notice a slight *ange ( "s sort 9 ! eye itself z ! vision is adju/$4 ,?is adju/m5t is made by muscles t pull or compress ! eye l5s s z to make x ?ick] = ne> objects & ?9n] = di/ant ones4 ,! eye ord9>ily does n see objects ne>] ?an #aj 94 cle>ly4 ,?is means t ! greate/ possible ?ick5+ ( l5s w n =m cle> images ^u ! ret9a if ! object is ne>] ?an #aj 94 7#be cm474 ,illu/ration3 ,,fig4 #chg4--,! visual angle1 ,,aob is great] at ,,ab ?an at ,a,b4 #cia4 ,! ,visual ,angle4--,to exam9e objects c>efully we usually br+ !m z close to ! eye z possible1 = ! ne>] to ! eye ! object is br\ght1 ! l>g] is ! visual angle =m$ by x 7see ,fig4 #chg71 & ! l>g] is its image ^u ! ret9a4 ,! visual angle ( an object is ! angle at ! eye l5s betwe5 ! rays t h come f ! ends ( ! object4 ,consequ5tly ! m di/ant ! object1 ! small] is its visual angle4 ,n[ if we wi% to exam9e small objects ) great c>e1 we frequ5tly f9d t x is necess>y to br+ !m close to ! eye s t !y h a visual angle ( adequate size4 ,if !y mu/ be br\ght clos] ?an #aj 94 a d\ble convex l5s is plac$ 9 front ( ! eye4 ,?is assi/s ! eye l5s 9 conv]g+ ! light s t a cle> image may be =m$ :5 ! object is close1 say an in* or s f ! eye4 ,?is is ! pr9ciple ( ! magnify+ glass us$ by wat*-mak]s & ( ! simple microscope4 ,! action ( ! latt] is illu/rat$ by ,fig4 #chh4 ,! convex l5s =ms a virtual1 enl>g$ image ,a-,b ( ! object ,a-,b :i* x obs]v$ in/ead ( ! object itself4 ,illu/ration3 ,,fig4 #chh4--;,action ( ! simple microscope4 ,illu/ration3 ,,fig4 #chi4--,ne> sight$ness1 or myopia4 ,p>allel rays come to a focus at ,f2 em]g+ rays focus at ,a1 ! f> po9t4 #cib4 ,defects ( ,vision4--,!re are sev]al defects ( vision t may be correct$ by spectacles or eye-glasses4 ,"o ( ^! is ne>-sight$ness4 ,x is due ei!r to an eyeball t is elongat$1 or to an eye l5s t is too convex1 or to bo? conditions4 ,?is condition br+s light f di/ant objects to a focus too soon 7z %[n 9 ,fig4 #chi74 ,only light f ne> objects w focus ^u ! ret9a 9 su* cases4 ,) normal vision light f di/ant or ne> objects may be focus$ )\t unusual ef=t ^u ! ret9a1 see ,fig4 #cij4 ,! rem$y = ne>-sight$ness is to use concave l5ses :i* w assi/ 9 prop]ly refract+ ! light s ! focus w be =m$ on ! ret9a 7,fig4 #cia74 ,f>-sight$ness is ! rev]se ( ne>-sight$ness2 ! eyeball is ei!r too %ort1 or ! l5s too flat1 or bo? conditions obta91 s t ! light ent]+ ! eye is br\ght to a focus beh9d ! eyeball 7,fig4 #cib74 ,! rem$y is convex l5ses :i* w assi/ 9 prop]ly conv]g+ ! light1 see ,fig4 #cic4 ,a ?ird defect is call$ a/igmatism4 ,?is is caus$ by "s irregul>ity or lack ( symmetry 9 ! eye4 ,x is correct$ by a cyl9drical l5s t comp5sates = ?is defect ( ! eye4 ,a diagram simil> to ,fig4 #cid is us$ z a te/ = a/igmatism4 ,if ! l9es appe> ) unequal di/9ctness1 "s irregul>ity ( refraction 7a/igmatism7 is indicat$4 ,illu/ration3 ,,fig4 #cij4--,! normal eye4 ,! p>allel rays ,a ,b focus )\t accommodative ef=t at ,c4 ,illu/ration3 ,,fig4 #cia4--;,correction ( ne>-sight$ness by concave l5s4 ,illu/ration3 ,,fig4 #cib4--;,f>-sight$ness or hyp]opia4 ,p>allel rays focus$ beh9d ! ret9a4 ,illu/ration3 ,,fig4 #cic4--;,correction ( f>-sight$ness by a convex l5s4 ,illu/ration3 ,,fig4 #cid4--,te/ c>d = a/igmatism4 #cic4 ,! ,photographic ,cam]a4--,?is is a light-tight box1 provid$ ) a convex l5s 9 front1 cov]+ an ap]ture & a gr\nd glass scre5 at ! back4 ,! di/ance betwe5 ! l5s & ! scre5 is adju/$ until a %>p image is obta9$ ^u ! latt]1 :i* is !n replac$ by a s5sitive plate or film4 ,! s5sitiz$ surface ( ! plate or film conta9s a salt ( silv] :i* is *ang$ by ! action ( light4 ,aft] ! plate has be5 expos$ to ! action ( light1 x is develop$ by ! use ( *emicals produc+ a negative image4 ,f negative1 by ! use ( s5sitiz$ pap]1 positive pr9ts may be secur$ :i* resemble ! object photograph$4 ,illu/ration3 ,,fig4 #cie4--;,diagram ( ! project+ lant]n4 #cid4 ,! project+ lant]n 7see ,fig4 #cie7 employs a /rong s\rce ( light1 z an electric arc lamp ,l1 to /rongly illum9ate a transp>5t picture1 or lant]n slide1 ,s1 a real image 7,i7 ( :i* is =m$ ^u a l>ge scre54 ,two l>ge plano-convex l5ses 7,c71 call$ cond5s+ l5ses1 are plac$ ne> ! lamp to conc5trate ! light ^u ! slide ,s4 ,! convex l5s =m+ ! image is call$ ! objective 7,o74 #cie4 ,! comp\nd microscope consi/s ( two l5ses4 ,"o call$ ! objective is plac$ ne> ! object to be view$4 ,?is l5s has a %ort focal l5g? usually less ?an a c5timet]4 ,x =ms a real image ( ! object4 ,a-,b4 ,! o!r l5s1 ! eyepiece =ms a virtual image ( ?is real image4 ,a-,b4 7,see ,fig4 #cif47 #cif4 ,! telescope consi/s ( two l5ses1 ! eyepiece & ! objective4 ,z 9 ! comp\nd microscope1 ! objective ( ! telescope =ms a real image ( ! di/ant object1 ! eyepiece =m+ an enl>g$ virtual image ( ! real image4 ,x is ! virtual image t is view$ by ! obs]v]4 7,see ,fig4 #cig47 ,9 ord] to collect suffici5t light f di/ant />s ! objective is made l>ge1 sometimes #ej 94 9 diamet]4 ,illu/ration3 ,,fig4 #cif4--;,=mation ( an image by a microscope4 ,a-,b is ! object4 ,b-,a ! real image =m$ by ! objective4 ,b-,a is ! virtual image =m$ by ! eyepiece4 ,! eye sees ! virtual image4 ,! l5g? ( ! telescope tube dep5ds ^u ! focal l5g? ( ! objective1 s9ce ! di/ance betwe5 ! two l5ses mu/ equal ! sum ( _! focal l5g?s4 ,illu/ration3 ,,fig4 #cig4--;,=mation ( an image by a telescope4 b-a is ! real image2 d-c is ! virtual image se5 by ! obs]v]4 #cig4 ,! op]a glass consi/s ( a convex l5s z objective & a concave l5s z an eyepiece4 ,! =m] t5ds to =m a real image b ! latt] div]ges ! rays be=e a real image c be =m$1 ! action ( ! two l5ses produc+ an enl>g$ virtual image 7z 9 ,fig4 #cih7 :i* is view$ by ! "o us+ ! glass4 ,! compact size ( ! op]a glass is due to ! fact t ! di/ance betwe5 ! two l5ses is ! diff]5ce ( ! focal l5g?s4 ,illu/ration3 ,,fig4 #cih4--;,=mation ( an image by an op]a-glass4 a-b is ! virtual image4 ,illu/ration3 ,,fig4 #cii4--;,diagram ( ! ,zeiss b9ocul> or prism field glass4 #cih4 ,! ,prism ,field ,glass or ,b9ocul>4--,?is in/rum5t4 has come into use 9 rec5t ye>s4 ,x possesses ! wide field ( view ( ! spy glass b is z compact z ! op]a glass4 ,?is compact =m is secur$ by caus+ ! light to pass back & =? betwe5 two "r-angle prisms 7z %[n 9 ,fig4 #cii74 ,?is device p]mits ! use ( an objective l5s ) a focal l5g? ?ree times t ( ! tube1 secur+ mu* great] magnify+ p[] ?an ! %ort in/rum5t w\ld o!rwise possess4 ,a fur!r advantage is secur$ by ! total reflection f ! two prisms1 "o ( :i* is plac$ s z to rev]se ! image "r = left & ! o!r inv]ts x1 s t :5 view$ 9 ! eyepiece x is 9 its prop] position4 ,important ,topics #a4 ,! eye3 p>ts1 =mation ( image1 k9d1 h[1 :]e4 #b4 ,eye defects1 h[ rem$i$4 ,visual angle4 #c4 ,simple microscope1 cam]a2 images1 k9d1 h[ =m$4 #d4 ,comp\nd microscope1 telescope & op]a glass2 images1 action ( ea* l5s4 ,ex]cises #a4 ,"n ?ree in/rum5ts 9 :i* l5ses =m virtual images & ?ree 9 :i* real images are =m$4 #b4 ,9 :at direction is an o> 9 wat] app>5tly b5t8 ,expla9 by a diagram4 #c4 ,:at optical in/rum5ts h y us$8 ,is ! visible image =m$ by ea* ( ^! real or virtual8 #d4 ,! focal l5g? ( a copy+ cam]a l5s is #ad 94 ,:]e mu/ a draw+ be plac$ s t an image ( ! same size may be =m$ ^u ! gr\nd glass scre58 ,:at mu/ be ! di/ance ( ! scre5 f ! l5s8 #e4 ,:at are two me?ods by :i* y c det]m9e ! focal l5g?s ( ! l5s ( a photographic cam]a8 #f4 ,! critical angle = wat] is #dh-a_/b degrees4 ,%[ by a diagram h[ mu* ( ! sky c be se5 by a div] :o looks upw>d ?r\gh ! wat]4 #g4 ,h[ is ne>-sight$ness caus$8 ,h[ is x correct$8 ,illu/rate by a diagram4 #h4 ,h[ is ! eye accommodat$ 7focus$7 z an object gradually approa*es x8 #i4 ,expla9 :y a simple microscope assi/s 9 look+ at ! p>ts ( a fl[] or insect4 #aj4 ,:y d p :o h good eyesight :5 "y require glasses z !y gr[ old8 7#g7 ,,color ,,& ,,spectra ,illu/ration3 ,,guglielmo ,,m>coni ,copyright by ,und]wood ,und]wood1 ,n4 ,y4 ,guglielmo ,m>coni 7,italy74 ,inv5tor ( wireless telegraphy4 ,illu/ration3 ,,alex&] ,,graham ,,bell ,copyright by ,und]wood ,und]wood1 ,n4 ,y4 ,alex&] ,graham ,bell1 ,wa%+ton1 ,d4 ,c4 ,inv5tor ( ! telephone4 #cii4 ,color4--,mu* ( ! pleasure exp]i5c$ 9 gaz+ at beautiful objects is due to ! color %[n by !m4 ,! blue sky1 ! gre5 grass1 & ! v>i$ t9ts ( fl[]s1 & ( ! ra9b[ all excite our admiration ,! /udy ( color beg9s naturally ) ! production ( ! spectrum1 ! _m-color$ image ^u a scre5 produc$ by pass+ a beam ( light ?r\gh a prism4 ,! spectrum is be/ %[n :5 ! light ent]s by a n>r[ slit 7,fig4 #djj74 ,! spectrum 0 fir/ produc$ by ,sir ,isaac ,newton 9 #afge by ! means j describ$4 ,! names usually giv5 to ! m prom95t colors ( ! spectrum are violet1 indigo1 blue1 gre51 yell[1 orange1 & r$4 ,! initials ( ^! names1 comb9$1 spell vibgyor1 a ^w )\t mean+ except to assi/ 9 rememb]+ ! ord] ( ! colors 9 a spectrum4 ,if ! light t has pass$ ?r\gh a prism is s5t ?r\gh a second prism plac$ 9 rev]se position 7see ,fig4 #dja71 ! light pass+ ?r\gh bo? prisms is f\nd to be :ite4 ,?is exp]im5t indicates t :ite light is compos$ ( light ( all colors4 ,illu/ration3 ,,fig4 #djj4--;,=mation ( ! spectrum by a prism4 ,illu/ration3 ,,fig4 #dja4--,! colors ( ! spectrum recomb9e to =m :ite light4 #djj4 ,disp]sion4--,! sep>ation ( ! colors by a prism is call$ disp]sion4 ,9 exp]im5t+ to f9d a reason = disp]sion1 x has be5 le>n$ t lights ( diff]5t colors are ( diff]5t wave l5g?s4 ,color 9 light is !re=e analog\s to pit* 9 s\nd4 ,we he> ?r\gh _m octaves1 b we see ?r\gh ab\t "o octave4 ,t is1 ! %orte/ visible waves ( violet light are ab\t #j4jjjjch cm4 9 l5g? :ile ! longe/ visible r$ rays are #j4jjjjgf cm41 or ! longe/ visible light waves are ab\t twice ! l5g? ( ! %orte/ visible ones4 ,x appe>s f ! evid5ce ( exp]im5ts ^u disp]sion t light waves ( diff]5t l5g?s are refract$ diff]5tly4 ,?is causes ! images =m$ by refraction ?r\gh simple glass l5ses to be fr+$ ) color & to lose "s ( _! %>pness & def9it5ess ( outl9e1 s9ce ! violet light is br\ght to a focus soon] ?an ! r$4 7,see ,fig4 #djb47 ,?is s]i\sly affects ! value ( su* l5ses = optical purposes4 ,=tunately x is f\nd t diff]5t k9ds ( glass h a diff]5t rate ( disp]sion = ! same am\nt ( refraction4 ,illu/ration3 ,,fig4 #djb4--,violet light comes to a focus soon] ?an r$4 #dja4 ,! ,a*romatic ,l5s4--,! exi/5ce ( ^! diff]5t k9ds ( glass makes possible a comb9ation ( l5ses 9 :i* disp]sion is entirely ov]come ) ! loss ( only ab\t "o-half ( ! refraction4 ,su* a comb9ation is %[n 9 ,fig4 #djc4 ,x is call$ an a*romatic l5s1 s9ce images =m$ by x are n color$ b :ite 7a )\t1 *roma color74 ,! a*romatic l5s consi/s ( a d\ble convex l5s ( cr[n glass comb9$ ) a plano-concave l5s ( fl9t glass4 ,a*romatic l5ses are us$ 9 all high-grade optical in/rum5ts su* z telescopes & microscopes4 ,! color$ images t are sometimes se5 9 *eap op]a glasses %[ ! result ( n us+ a*romatic l5ses4 ,illu/ration3 ,,fig4 #djc4--;,an a*romatic l5s4 ,c is ( cr[n glass2 ,f1 ( fl9t glass4 #djb4 ,! ,color ( ,bodies4--,project ! spectrum ( sunlight ^u a :ite surface 9 a d>k5$ room4 ,n[ place 9 diff]5t p>ts ( ! spectrum objects ( v>i\s colors4 ,r$ objects w %[ brilliant r$ :5 at ! r$ end ( ! spectrum b look black at ! blue end1 :ile blue objects appe> blue only at ! blue end4 ,^! facts indicate t ! color ( an object dep5ds ^u two ?+s3 7a7 ! light t falls ^u x & 7b7 ! light :i* x s5ds to ! eye4 ,a black surface absorbs all color :ile a :ite "o reflects all wave l5g?s to ! eye 9 ! same proportion t !y come to x4 ,a :ite object w appe> r$ 9 r$ light1 & blue 9 blue light s9ce x reflects bo? ( ^!4 ,a color$ object reflects light ( its own color b absorbs all o!rs4 ,! color !n ( a body is due to ! light :i* x does n absorb1 b :i* comes f x to ! eye4 #djc4 ,! color ( transp>5t bodies1 su* z color$ glass1 is due to ! pres5ce ( a dye or pigm5t conta9$ 9 ! body4 ,?is pigm5t absorbs a "p ( ! light1 ! "p transmitt$ giv+ ! color4 ,?is may be %[n by hold+ a %eet ( color$ glass 9 a beam ( light ei!r be=e or aft] x has pass$ ?r\gh a prism4 ,"s colors1 z r$1 may be f\nd to be ne>ly pure1 only ! r$ pass+ ?r\gh1 :ile gre5 glass (t5 transmits 9 addition to ! gre5 "s yell[ & "s r$ light4 #djd4 ,complem5t>y ,colors4--,if two prisms are plac$ 9 rev]s$ position ne> ea* o!r 7see ,fig4 #dja71 a beam ( light disp]s$ by "o is recomb9$ into :ite light by ! o!r4 ,if n[ a c>d is held betwe5 ! two prisms s z to cut (f "s ( ! color$ light1 say ! r$1 ! rema9+ light w be f\nd to =m a gre5i% blue4 ,if ! c>d is remov$1 ! light becomes :ite aga94 ,t is1 r$ & peacock blue light toge!r =m :ite4 ,any two colors t toge!r =m :ite light are call$ complem5t>y4 ,o!r complem5t>y colors are light yell[ & blue1 gre5 & crimson1 orange & gre5i% blue1 violet & gre5i% yell[4 ,we mu/ n confuse ! comb9+ ( colors 7light7 & ! comb9+ ( pigm5ts1 ! latt] consi/+ ( bodies t absorb light4 ,yell[ pigm5t absorbs all b yell[ & "s gre51 :ile blue pigm5t absorbs all b blue & "s gre54 ,mix+ ^! two pigm5ts causes ! absorption ( all colors b gre54 ,blue & yell[ pa9t mix$ produce gre51 :ile blue & yell[ light give :ite4 #dje4 ,! sol> spectrum1 z ! spectrum ( sunlight is call$1 may be obs]v$ 9 ! ra9b[4 ,! latt] is produc$ ?r\gh ! disp]sion ( light by sph]ical ra9drops4 ,its =mation may be imitat$ by s5d+ a small circul> beam ( light ?r\gh a scre5 aga9/ a r\nd glass flask fill$ ) wat]4 7,see ,fig4 #djd47 ,! light passes ?r\gh ! wat] & is disp]s$ :5 x ent]s & :5 x leaves1 produc+ a color ^u ! scre5 at ,r-,v4 ,! c\rse ( ! light )9 ! drop is indicat$ 9 ,fig4 #dje4 ,! violet ray comes to ! eye m ne>ly horizontal & is !re=e bel[ r$1 z we look at ! ra9b[4 #djf4 ,fraunh(] ,l9es4--,"s ( ! mo/ important features ( ! sol> spectrum are n se5 9 ! ra9b[ or 9 ! b& ( light usually obs]v$ ^u a scre54 ,by ! use ( a n>r[ slit & a convex l5s to c>efully focus ! slit ^u a :ite scre5 x is se5 t ! sol> spectrum is cross$ by _m d>k l9es4 ,^! are call$ ,fraunh(] l9es1 to honor ! ,g]man sci5ti/ :o 9 #ahad fir/ accurately det]m9$ _! position4 ,two exp]im5ts ) a spectroscope w help to make cle> ! mean+ ( ! ,fraunh(] l9es4 ,illu/ration3 ,,fig4 #djd4--;,a ra9b[ =m$ by a beam ( light /rik+ a flask ( wat]4 ,illu/ration3 ,,fig4 #dje4--,! c\rse ( a beam ( light )9 a drop ( wat]4 #djg4 ,! ,spectroscope & ,its ,uses4--,! spectroscope 7,fig4 #djf7 is an in/rum5t = obs]v+ spectra4 ,x consi/s ( a prism1 a slit1 & a convex l5s ,t = focus+ an image ( ! slit accurately ^u a scre5 7,fig4 #djg7 :]e ! spectrum is obs]v$ ?r\gh ! eyepiece ,e4 ,illu/ration3 ,,fig4 #djf4--,! spectroscope4 7,a7 ,a ,buns5 flame is plac$ 9 front ( ! slit & a heat$ plat9um wire :i* has be5 dipp$ 9 common salt or "s sodium comp\nd plac$ 9 ! ,buns5 flame2 ! latt] becomes yell[ & a vivid yell[ l9e is obs]v$ on ! scre5 9 ! spectroscope4 ,o!r sub/ances1 z b>ium & /rontium salts1 :5 heat$ to inc&esc5ce 9 ! ,buns5 flame1 give *>act]i/ic bright l9es4 ,9 fact ea* elem5t has be5 f\nd to h its own *>act]i/ic set ( color$ l9es4 ,?is fact is made use ( 9 spectrum analysis1 by :i* ! pres5ce ( c]ta9 elem5ts 9 a sub/ance c be def9itely prov$ ^u ! appe>ance ( its p>ticul> l9es 9 ! spectrum4 ,illu/ration3 ,,fig4 #djg4--;,diagram ( a spectroscope4 ,illu/ration3 ,,fig4 #djh4--,! bright l9e spectrum ( iron & its co9cid5ces ) "s ( ! d>k l9es ( ! sol> spectrum4 7,b7 ,if light f1 = example1 an arc light is s5t ov] a gas flame conta9+ sodium vapor1 a d>k l9e appe>s 9 ! spectrum--9 ! exact position 9 :i* ! yell[ sodium l9e appe>$4 ,x seems t ! sodium vapor removes f :ite light ! same wave l5g?s t x itself produces4 ,?is absorption is suppos$ to be due to sympa!tic vibration2 j z a tun+ =k is set 9 vibration by ! waves ( ano!r =k 9 unison ) x1 at ! same "t absorb+ ! wave en]gy1 s 9 ! gas flame ! sodium p>ticles absorb ! wave motion ( ! same vibration rate z t emitt$ by !m4 ,! fact t ! spectrum ( sunlight conta9s a great _m d>k l9es is believ$ to indicate t ! sun is surr\nd$ by cl\ds =m$ by ! vaporization ( ! v>i\s sub/ances 9 ! sun itself4 ,by comp>+ ! d>k l9es ( ! sol> spectrum ) ! bright-l9e spectra ( v>i\s sub/ances f\nd 9 ! e>?1 su* an exact correspond5ce ( ! l9es is f\nd t ! pres5ce ( ! vapor ( ^! sub/ances ab\t ! sun is consid]$ prov$4 7,see ,fig4 #djh :i* %[s ! exact correspond5ce betwe5 ! bright-l9e spectrum ( iron vapor & ! d>k l9es appe>+ 9 a portion ( ! sun's spectrum47 ,! spectra ( ! />s also conta9 c]ta9 d>k l9es4 ,?us ! pres5ce ( ! correspond+ sub/ances 9 di/ant />s is consid]$ z det]m9$4 #djh4 ,!ory ( ,color ,vision4--,by comb9+ light ( ! ?ree colors r$1 gre5 & blue-violet 9 prop] proportions1 x has be5 f\nd possible to produce any color effect1 ev5 :ite4 ,?is leads to ! conclusion t 9 ! ret9a ( ! eye are ?ree diff]5t k9ds or sets ( s5sitive n]ve end+s1 s5sitive respectively to r$1 to gre51 & to blue light4 ,?is idea is giv5 corroboration by "s facts ( color bl9dness4 ,?us "s p]sons h no s5sation ( r$1 ?is color n be+ di/+ui%$ f gre54 ,o!rs are color bl9d to gre5 or blue4 ,x is suppos$ t 9 color bl9d p]sons "o ( ! sets ( n]ve end+s s5sitive to "o ( ^! ?ree colors is lack+4 #dji4 ,?ree-color ,pr9t+4--,s9ce all colors may be produc$ by mix+ ! ?ree colors1 light r$1 gre51 & blue-violet1 ^! are call$ ! ?ree prim>y colors4 ,! s-call$ prim>y pigm5ts or pa9ts are simply ! complem5ts ( ! ?ree prim>y colors4 ,!y are1 9 ord]1 peacock blue1 crimson1 & light yell[4 ,! ?ree pigm5ts :5 mix$ yield black1 s9ce comb9$ !y absorb all k9ds ( visible light4 ,! process ( ?ree-color pr9t+1 n[ s g5]ally employ$ 9 pr9t+ color$ pictures = books1 cal5d>s1 etc41 consi/s 9 comb9+ ^u :ite pap] ?ree color$ impressions1 us+ successively ! ?ree prim>y pigm5ts 7yell[1 crimson & blue7 f plates prep>$ z foll[s3 ,?ree photographs ( a giv5 color$ object are tak51 ea* ?r\gh a diff]5t %eet ( gelat9e call$ a filt]1 /a9$ ! color ( "o ( ! prim>y colors4 ,f ^! photographs half-tone blocks are made 9 ! usual way4 ,! color$ picture is made by c>efully sup]pos+ impressions f ^! blocks1 us+ 9 ea* case an ink ^: color is ! complem5t ( ! filt] ?r\gh :i* ! orig9al picture 0 tak54 ,an illu/ration ( ! process is giv5 ^u ! plate 9 ! frontispiece ( ?is book4 ,important ,topics #a4 ,color1 due to wave l5g?2 disp]sion by prism1 sph]e 9 ra9b[1 complem5t>y colors1 color ( opaque & transp>5t bodies4 #b4 ,spectra1 sol>2 =mation ( ra9b[2 bright-l9e spectra1 h[ =m$1 h[ us$2 d>k-l9e1 h[ =m$1 us$4 #c4 ,!ory ( color vision4 ,?ree color pr9t+4 ,ex]cises #a4 ,h[ does a :ite fl[] look :5 view$ ?r\gh a blue glass8 ,?r\gh a r$ glass8 ,?r\gh a r$ & blue glass at ! same "t8 #b4 ,:y does a r$ ribbon appe> black :5 se5 by blue light & r$ :5 se5 by r$ light8 #c4 ,9 :at "p ( ! sky mu/ y look to see a ra9b[ 9 ! morn+8 ,9 ! aft]noon8 ,expla94 #d4 ,h[ w\ld y arrange two simil> prisms s z to produce d\ble ! deviation produc$ by "o8 #e4 ,! color ( an object dep5ds ^u :at two ?+s8 #f4 ,:at k9d ( a spectrum %\ld moonlight give8 ,:y8 #g4 ,a mixture ( gre5 & r$ lights gives a s5sation ( yell[4 ,c y sugge/ :y a mixture ( blue & yell[ lights gives ! s5sation ( :ite8 7#h7 ,,nature ,,( ,,light1 ,,int]f]5ce1 ,,pol>ization #daj4 ,! ,corpuscul> ,!ory4--,! !ory ( ! nature ( light t 0 mo/ g5]ally accept$ until ab\t ! ye> #ahjj1 held t light consi/s ( /reams ( m9ute p>ticles1 call$ corpuscles1 mov+ at enorm\s velocities4 ,?is corpuscul> !ory 0 9 accord ) ! facts ( reflection & ! rectil9e> motion ( light1 b 0 ab&on$ aft] ! discov]y ( ! int]f]5ce ( light1 z x c\ld n acc\nt = ! latt] ph5om5on4 #daa4 ,! ,wave ,!ory ( ,light4--,! !ory t light is a =m ( wave motion 0 fir/ advanc$ by ,huyg5s1 a ,dut* physici/1 9 ! sev5te5? c5tury4 ,?is !ory 0 oppos$ at ! />t s9ce 7,a7 no m$ium 0 kn[n to exi/ :i* w\ld convey wave motion ?r\gh space1 z f ! sun to ! e>?1 & 7,b7 ! rectil9e> motion ( light 0 unlike t ( any o!r =m ( kn[n wave motions1 su* z t ( wat] or ( s\nd waves :i* are able to b5d ar\nd corn]s4 ,9 answ] to ! fir/ objection1 ,huyg5s assum$ ! pres5ce ( a m$ium :i* he nam$ e!r1 :ile ! second objection has be5 completely ov]come dur+ ! pa/ c5tury by ! discov]y t light may deviate f a /raight l9e4 ,x is n[ kn[n t ! excessive %ortness ( light waves is ! reason = its /raight-l9e motion4 ,fur!r1 long e!r waves1 z ^? ( wireless telegraphy1 are f\nd to b5d ar\nd ob/acles 9 a mann] simil> to ^? ( wat] or s\nd4 ,illu/ration3 ,,fig4 #dji4--,two plates press$ toge!r by a screw clamp4 ,illu/ration3 ,,fig4 #daj4--;,illu/rat+ ! int]f]5ce ( light by a ?9 film ( air4 #dab4 ,! int]f]5ce ( light is "o ( ! ph5om5a = :i* ! wave !ory (f]s ! only satisfactory explanation4 ,int]f]5ce ( light may be %[n by tak+ two pieces ( plate glass & =cibly press+ !m toge!r by a screw clamp1 z %[n 9 ,fig4 #dji4 ,aft] a c]ta9 pressure has be5 rea*$1 color$ r+s w appe> ab\t ! compress$ spot :5 view$ by light reflect$ f ! upp] surface ( ! glass4 ,if light ( "o color1 su* z t transmitt$ by r$ glass1 falls ^u ! app>atus1 ! r+s are se5 to be alt]nately r$ & d>k b&s4 ,! explanation ( ?is ph5om5on accord+ to ! wave !ory is z foll[s3 ,! two %eets ( glass1 al?\gh tightly press$ toge!r1 are sep>at$ 9 mo/ places by a ?9 w$ge ( air 7see ,fig4 #daj71 :i* repres5ts 9 an exagg]at$ =m ! b5d+ ( ! plates :5 press$ by ! clamp4 ,sev]al waves are repres5t$ z com+ f ! "r & ent]+ ! glass4 ,n[ ! wave mov+ f ,r to ! plates has "s ( its light reflect$ f ea* glass surface4 ,consid] ! two portions ( ! wave reflect$ at ea* ( ! surfaces betwe5 ! plates1 i4e41 f ! two surfaces ( ! w$ge ( air4 ,if ! portion ( ! wave reflect$ f ! second surface ( ! air w$ge comb9es ) t reflect$ f ! fir/ surface1 9 ! same phase z at ,c1 ! two reflect$ waves /r5g!n ea* o!r4 ,:ile if ! two reflect$ portions ( ! wave meet 9 opposite phases z at ,a & ,b1 a decrease or a complete ext9ction ( ! light results4 ,?is is call$ int]f]5ce4 ,if light ( "o wave l5g? is us$1 z r$ light1 ! regions ( re9=cem5t & int]f]5ce are %[n by r$ & d>k r+s1 :ile if :ite light is us$1 ! r+ :]e r$ light int]f]es1 yields its complem5t>y color1 gre5i% blue4 ,:]e int]f]5ce ( gre5i% blue occurs1 r$ is f\nd1 etc4 ,_m ph5om5a are due to int]f]5ce1 su* z 7,a7 ! color ( ?9 films ( oil on wat]1 :]e ! portions ( light reflect$ f ! two surfaces ( ! oil film int]f]e result+ 9 ! production ( color2 7,b7 ! color ( soap bubbles4 ,:5 fir/ =m$1 soap-bubble films are n ?9 en\gh to %[ int]f]5ce well1 b z ! bubbles increase 9 size or become ?9n] on /&+1 ! conditions = int]f]5ce are rea*$ &1 z ! film becomes ?9n]1 a regul> succession ( colors is notic$4 #dac4 ,diff]5ces ,betwe5 ,light & ,s\nd4--,among ! important diff]5ces betwe5 light & s\nd t h be5 consid]$ are ! foll[+3 ! =m] are 7a7 waves 9 ! e!r1 7b7 ( v %ort wave l5g?1 & 7c7 _! motion is 9 /raight l9es4 ,ano!r diff]5ce 7d7 is 9 ! mode ( vibration4 ,s\nd waves are longitud9al1 :ile light waves are transv]se4 ,light waves consi/ ( vibrations ( ! e!r at "r angles to ! l9e ( motion4 ,to illu/rate ! reason+ t has l$ to ?is conclusion1 suppose a rope to be pass$ ?r\gh two v]tical grat+s4 7,see ,fig4 #daa1 #a47 ,if ! rope be set 9 transv]se vibration by a h&1 ! waves produc$ w readily pass ?r\gh to ! grat+s ,p & ,q & cont9ue 9 ! "p ext5d+ beyond ,q4 ,if1 h[ev]1 ,q is at "r angles to ,p1 no motion w be f\nd beyond ,q4 ,n[ if a /ret*$ coil$ spr+ ) longitud9al vibrations %\ld take ! place ( ! rope1 x is evid5t t ! cross$ position ( ! two grat+s w\ld (f] no ob/acles to ! movem5t ( ! vibration4 ,9 o!r words1 cross$ grat+s (f] no ob/ruction to longitud9al vibrations1 :ile !y may completely /op transv]se vibrations4 ,illu/ration3 ,,fig4 #daa4--,transv]se waves w pass ?r\gh bo? grat+s 9 7#a7 :]e ! op5+s 9 ! two grat+s are at "r angles4 ,! waves pass+ ,p are /opp$ by ,q 7#b74 ,illu/ration3 ,,fig4 #dab4--;,effect ( t\rmal9e cry/als on light4 #dad4 ,pol>ization ( ,light4--,x is f\nd t two cry/als ( t\rmal9e behave t[>d light j z ! two grat+s behave ) respect to ! transv]se waves ( ! rope4 ,?us1 if a small op5+ 9 a scre5 is cov]$ ) a t\rmal9e cry/al1 light comes ?r\gh b slightly dim9i%$ 9 int5sity4 ,if a second cry/al is plac$ ov] ! fir/ "o s t ! two axes are 9 ! same direction z 9 ,fig4 #dab,p1 light is z freely transmitt$ ?r\gh ! second cry/al z ?r\gh ! fir/1 b if ! cry/als are cross$ 7,fig4 #dab,s7 no light passes ! second cry/al4 ,?is exp]im5t %[s t ! light :i* has pass$ ?r\gh "o t\rmal9e cry/al w pass ?r\gh ano!r only :5 ! latt] is held 9 a c]ta9 position1 h5ce x is believ$ t a t\rmal9e cry/al is capable ( transmitt+ light t is vibrat+ 9 "o p>ticul> plane4 ,! direct conclusion f ?is is t light waves are transv]se r ?an longitud9al4 ,! exp]im5t j describ$ illu/rates :at is call$ pol>ization ( light4 ,! beam t aft] pass+ ?r\gh a 7,fig4 #dab7 is unable to pass ?r\gh b1 if ! two axes are cross$1 is call$ a pol>iz$ beam4 ,! conclusion t light waves are transv]se is !re=e bas$ ^u ! ph5om5on ( ! pol>ization ( light4 ,?is 0 fir/ discov]$ by ,huyg5s 9 #afij4 ,important ,topics #a4 ,int]f]5ce ( light3 evid5ce1 reason+ involv$1 illu/ration4 #b4 ,pol>ization ( light3 evid5ce1 reason+ involv$4 #c4 ,nature ( light1 diff]5ces betwe5 s\nd & light4 ,ex]cises #a4 ,make a li/ ( ! diff]5ces betwe5 s\nd & light & /ate briefly ! evid5ce ^u :i* ! k ( ^! diff]5ces is bas$4 #b4 ,:y w a ?ickness ( film t w produce int]f]5ce ( r$ light be diff]5t f t produc+ int]f]5ce = gre5 or blue8 #c4 ,us+ ! =mula n v_/l compute ! vibration rate = violet light if its wave l5g? is consid]$ z #j4jjjjd cm4 #d4 ,expla9 h[ ! fact ( pol>ization affects ! wave !ory ( light4 #e4 ,%[ h[ x is possible by comp>+ ! spectrum ( ! sun ) t ( a /> to tell :e!r ! /> is approa*+ or rec$+ f ! e>?4 ,review ,outl9e3 ,light ,light2 spe$1 s\rce1 m$ium4 ,/raight ,l9e ,motion2 %ad[1 umbra1 p5umbra1 eclipse1 image4 ,photometry2 ,law ( int5sity1 c&le p[]1 foot-c&le4 ,mirrors2 ,law ( reflection2 image--real1 virtual2 plane1 curv$1 p>abolic1 mirrors4 ,refraction2 cause & effects2 plate1 prism1 l5s2 total reflection4 ,l5ses2 six =ms1 pr9cipal focus1 c5t]1 l5s equation1 #a_/;,f #a_/;,do #a_/;,di4 ,optical in/rum5ts2 eye1 defects & correction1 cam]a1 microscope1 etc4 ,spectra2 #c k9ds1 disp]sion1 production ( color effects1 spectroscope1 uses4 ,nature ( ,light2 wave !ory1 int]f]5ce1 pol>ization1 significance4 ,,*apt] ,,xvii ,,invisible ,,radiations 7#a7 ,,electric ,,waves ,,& ,,radio-,,activity #dae4 ,oscillatory ,nature ( ! ,sp>k f a ,leyd5 ,j>4--,9 /udy+ s\nd 7,art4 #cci71 ! sympa!tic vibration ( two tun+ =ks hav+ ! same rate ( vibration 0 giv5 z an illu/ration ( resonance4 ,! conditions = obta9+ electrical resonance by ! use ( two ,leyd5 j>s are giv5 9 ! foll[+ exp]im5t4 ,jo9 ! two coats ( a ,leyd5 j> 7,fig4 #dac7 to a loop ( wire ,l1 ! slid+ crosspiece ,m be+ arrang$ s t ! l5g? ( ! loop may be *ang$ z desir$4 ,also place a /rip ( t9foil 9 contact ) ! inn] coat+ & br+ x ov] to )9 ab\t a millimet] ( ! out] coat+ z indicat$ at ,g4 ,n[ jo9 ! out] coat+ ( ano!r exactly simil> j> ,a to a wire loop ( fix$ l5g?1 ! end ( ! loop be+ sep>at$ f ! knob connect$ to ! inn] coat+1 a %ort di/ance at ,p4 ,place ! j>s ne> ea* o!r ) ! wire loops p>allel & connect coat+s ( ,a to ! t]m9als ( a /atic ma*9e or an induction coil4 ,at ea* dis*>ge betwe5 ! knobs at ,p1 a sp>k w appe> 9 ! o!r j> at ,g1 if ! crosspiece ,m is s adju/$ t ! areas ( ! two loops are exactly equal4 ,:5 ! wire ,m is mov$ s z to make ! areas ( ! two loops q unequal1 ! sp>k at ,g disappe>s4 ,illu/ration3 ,,fig4 #dac4 ,! exp]im5t j describ$ %[s t two electrical circuits c be tun$ by adju/+ _! l5g?s1 j z two tun+ =ks may be made sympa!tic by adju/+ _! l5g?s4 ,?is fact indicates t ! dis*>ge ( ! ,leyd5 j> is oscillatory1 s9ce resonance c pla9ly n be secur$ except betwe5 bodies hav+ natural p]iods ( vibration4 ,?is same fact is also %[n by exam9+ ! dis*>ge ( a ,leyd5 j> z x appe>s :5 view$ 9 a rapidly revolv+ mirror4 7,see ,fig4 #dad47 ,! appe>ance 9 ! mirror %[s t ! dis*>ge is made up ( a numb] ( sp>ks1 (t5 a doz5 or m1 vibrat+ back & =? until !y f9ally come to re/4 ,! "t ( "o vibration v>ies f "o million? to "o hundr$ million? ( a second1 dep5d+ on ! space betwe5 ! dis*>g+ balls & ! size ( ! j>s4 ,illu/ration3 ,,fig4 #dad4--,photograph ( ! oscillatory dis*>ge ( a ,leyd5 j>4 ,! dis*>ge ( a ,leyd5 j> or ( ano!r cond5s] sets up e!r waves t h ! spe$ ( light4 ,he9ri* ,h]tz 9 ,g]many fir/ prov$ ?is 9 #ahhh4 ,^! waves are n[ kn[n z ,h]tzian waves4 ,! l5g? ( ^! v>ies f #c cm4 to sev]al miles1 dep5d+ ^u ! size & conditions ( ! dis*>g+ circuit4 ,illu/ration3 ,,fig4 #dae4--;,a coh]]4 #daf4 ,! ,coh]]4--,! coh]] is a device = detect+ electric waves4 ,x consi/s ( a glass tube ) metal fil+s loosely pack$ betwe5 two metal plugs t fit ! tube closely4 7,see ,fig4 #dae47 ,^! fil+s (f] a high resi/ance to ! passage ( an electric curr5t1 b :5 electric waves pass ?r\gh ! fil+s ^! coh]e & all[ a weak curr5t to pass ?r\gh4 ,?is curr5t may be /rong en\gh to op]ate a relay connect$ ) a s\nd] or bell t gives audible signals4 ,if ! tube be tapp$ ! fil+s w be di/urb$ & ! resi/ance aga9 made s high t no curr5t c pass ?r\gh4 #dag4 ,wireless ,telegraphy4--,9 #ahid ,m>coni1 !n a "y man ( tw5ty1 :ile mak+ "s exp]im5ts ) electrical dis*>ges discov]$ t ! coh]] w\ld detect electrical waves at a consid]able di/ance f _! s\rce & t by ! use ( a telegraph key ! dots & da%es ( ! telegraph code c\ld be reproduc$ by a s\nd] atta*$ to a relay4 ,at pres5t ! coh]] is us$ pr9cipally 9 laboratory app>atus1 z mu* m s5sitive detectors are n[ available = comm]cial "w4 ,! ess5tial p>ts ( a mod]n wireless telegraph app>atus z us$ 9 _m comm]cial /ations are %[n 9 ,fig4 #daf4 ,alt]nat+ curr5t at #aaj volts is s5t into ! prim>y1 ,p1 ( a trans=m]1 ! second>y1 ,s1 ( :i* produces a pot5tial ( #ejjj to #bj1jjj volts4 ,! second>y *>ges a cond5s] until its pot5tial becomes high en\gh to produce a dis*>ge across a sp>k gap1 ,,sg4 ,?is dis*>ge is oscillatory1 ! frequ5cy be+ at ! rate ( ab\t "o million a second1 dep5d+ ^u ! capacity ( ! cond5s] & ! induction ( ! circuit4 ,^! oscillations pass ?r\gh ! prim>y ( ! oscillation trans=m]1 induc+ 9 ! second>y1 electric oscillations :i* surge back & =? ?r\gh ! ant5n1 or a]ial wires1 ,a4 ,^! oscillations set up ! wireless waves4 ,! production ( ^! waves is expla9$ z foll[s3 ,an electric curr5t 9 a wire sets up a magnetic field spread+ out ab\t ! conductor2 :5 ! curr5t /ops ! field returns to ! conductor & disappe>s4 ,! oscillations 9 ! ant5n1 h[ev]1 h su* a high frequ5cy1 ( ! ord] ( a million a second1 t :5 "o surge ( electricity sets up a magnetic field1 ! rev]se surge imm$iately foll[+ sets up an opposite magnetic field be=e ! fir/ field c return to ! wire4 ,"u ^! conditions a succession ( oppositely direct$ magnetic fields are produc$ :i* move out f ! ant5n ) ! spe$ ( light & induce electric oscillations 9 any conductors cut by !m4 ,illu/ration3 ,,fig4 #daf4--;,diagram ( a comm]cial wireless telegraph app>atus4 ,:ile ! electric waves are radiat$ 9 all directions f ! a]ial1 ! l5g? ( ! waves set up is approximately f\r times ! comb9$ l5g? ( ! a]ial wires & ! lead 9 connection to ! oscillation trans=m]4 ,! electric waves induce effective electrical oscillations 9 ! a]ial ( ! receiv+ /ation1 ev5 at di/ances ( hundr$s ( miles1 provid$ ! receiv+ trans=m]1 ,,rt1 is tun$ 9 resonance ) ! transmitt+ app>atus by adju/m5ts ( ! v>iable cond5s]1 ,,vc1 & ! load+ coil1 ,l4 ,! detector ( ^! oscillations 9 ! receiv+ trans=m] is simply a cry/al ( silicon or c>borundum1 ,d1 9 s]ies ) two telephone receiv]s1 ,ph4 ,! cry/al detector p]mits ! electric oscillations to pass ?r\gh x 9 "o direction only4 ,if ! cry/al did n possess ?is prop]ty1 ! telephone c\ld n be us$ z a receiv] z x _c respond to high frequ5cy oscillations4 ,:ile "o sp>k passes at ,,sg1 an int]mitt5t curr5t passes ?r\gh ! receiv] 9 "o direction4 ,s9ce "s #cjj to #abjj sp>ks pass ea* second at ,,sg :ile ! key1 ,k1 is clos$1 ! op]ator at ,ph he>s a musical note ( ?is frequ5cy z long z ,k is depress$4 ,%ort & long tones !n correspond to ! dots & da%es ( ord9>y telegraphy4 ,9 ord] to ma9ta9 a uni=m tone a rot>y sp>k gap1 z %[n1 is (t5 us$4 ,?is insures a tone ( fix$ pit* by mak+ uni=m ! rate ( produc+ sp>ks4 ,! ,cont95tal in/ead ( ! ,morse code ( signals is g5]ally employ$ 9 wireless telegraphy1 s9ce ! =m] employs only dots & da%es4 ,! latt] code employs1 9 addition to dots & da%es1 spaces :i* h sometimes caus$ confusion 9 receiv+ wireless messages4 ,! ,unit$ ,/ates gov]nm5t has adopt$ ! regulations ( ! ,int]national ,radio ,congress :i* directs t comm]cial companies %all use wave l5g?s betwe5 #cjj & #fjj or above #afjj met]s4 ,amateurs may use wave l5g?s less ?an #bjj met]s & no o!rs1 :ile ! gov]nm5t res]ves ! "r to wave l5g?s ( #fjj to #afjj met]s4 ,see p4 #dei = ,cont95tal telegraph code4 #dah4 ,dis*>ges 9 ,r>efi$ ,air4--,fig4 #dag repres5ts a glass tube #fj or m c5timet]s long1 atta*$ to an air pump4 ,connect ! ends ( ! tube to ! t]m9als ( a /atic ma*9e or ( an induction coil1 a-b4 ,at fir/ no sp>ks w pass betwe5 a & f1 because ( ! high resi/ance ( ! air 9 ! tube4 ,^u exhau/+ ! air 9 ! tube1 h[ev]1 ! dis*>ge beg9s to pass ?r\gh x in/ead ( betwe5 a & b4 ,?is %[s t an electrical dis*>ge w pass m readily ?r\gh a p>tial vacuum ?an ?r\gh air at ord9>y pressure4 ,z ! air becomes m & m exhau/$1 ! "* ( ! dis*>ge *anges4 ,at fir/ x is a fa9t sp>k1 gradually *ang+ until x becomes a gl[ ext5d+ f "o t]m9al to ! o!r & ne>ly fill+ ! tube4 ,illu/ration3 ,,fig4 #dag4--;,an ,aurora tube4 ,geissl] tubes are tubes l ! above4 ,!y are usually made ( diff]5t k9ds ( glass twi/$ into v>i\s %apes to produce beautiful color effects4 ,! aurora borealis or nor!rn light is suppos$ to be electric dis*>ges ?r\gh r>efi$ air at ! height ( f #fj to #ajj miles above ! e>?'s magnetic poles4 7,see ,fig4 #dah47 ,illu/ration3 ,,fig4 #dah4--;,aurora ,borealis4 #dai4 ,ca?ode ,rays4--,:5 ! tube 9 ,art4 #dbj is exhau/$ to a pressure ( #j4jja mm41 or a little less ?an "o million? ( an atmosph]e1 ! "* ( ! dis*>ge is entirely *ang$4 ,! tube becomes fill$ ) a yell[i% gre5 phosphoresc5t light4 ,?is is produc$ by :at are call$ ca?ode rays /rik+ ! glass walls ( ! tube4 ,^! rays are call$ ca?ode rays because !y come f ! ca?ode ( ! tube4 ,!y are invisible & t !y travel 9 /raight l9es is %[n by ! %ad[ obta9$ by us+ a tube ) a scre5 7,fig4 #dai74 ,illu/ration3 ,,fig4 #dai4--;,a ca?ode ray tube4 #dbj4 ,x ,rays4--,9 #ahie1 ,pr(essor ,rntg5 ( ,wurtzburg1 ,g]many1 discov]$ t :5 ! ca?ode rays /rike ! walls ( ! tube or any solid )9 x !y excite a =m ( invisible radiation4 ,?is radiation is call$ ,rntg5 rays1 or m commonly1 ,x rays4 ,c>eful exp]im5ts %[ t !y travel 9 /raight l9es1 & t !y c n be reflect$ or refract$ z light waves are4 ,!y pass ?r\gh glass & opaque objects su* z fle%1 c>dbo>d1 clo?1 lea!r1 etc41 b n ?r\gh metallic sub/ances4 ,! tube 9 ,fig4 #dbj has a scre5 cov]$ ) cry/als :i* become lum9\s :5 /ruck by ! ca?ode rays4 ,on br++ a magnet ne> ! tube ! lum9\s l9e is rais$ or l[]$ %[+ t ! magnetic field affects ! /ream ( ca?ode rays1 attract+ x :5 9 "o position b repell+ x :5 9 ! rev]se direction4 ,! ca?ode rays :i* cause ! bright l9e possess a negative *>ge ( electricity4 ,!y are n[ believ$ to be electrons %ot (f f ! surface ( ! ca?ode ) spe$s t may rea* #ajj1jjj miles a second4 ,x rays possess no electrical *>ge :atev] & _c be deflect$ by a magnet4 ,!y produce ! same effect on a photograph plate z light does1 only m sl[ly4 ,h5ce1 !y c be us$ 9 tak+ ,x ray photographs4 ,c]ta9 cry/als1 l b>ium plat9um cyanide1 fluoresce :5 /ruck by ! ,x rays4 ,! fluoroscope is ! "n giv5 to a light-tight box clos$ at "o end by a c>dbo>d cov]$ ) ^! cry/als 7,fig4 #dba74 ,on look+ into ! fluoroscope ) an opaque object su* z ! h& plac$ betwe5 ! scre5 & ! ,x ray tube1 a %ad[ ( ! bones ( ! h& c be se5 ^u ! scre5 ( ! fluoroscope4 7,see ,fig4 #dbb47 ,illu/ration3 ,,fig4 #dbj4--,! /ream ( ca?ode rays is deflect$ by a magnet4 ,illu/ration3 ,,fig4 #dba4--;,a fluoroscope4 ,illu/ration3 ,,fig4 #dbb4--;,a view ( ! %ad[ ( a h& z se5 9 a fluoroscope4 ,a special =m ( ! tube is us$4 7,see ,fig4 #dbc47 ,9 ?is tube a plat9um disc is plac$ at ! focus ( ! concave ca?ode4 ,?is conc5trates ! ,x rays 9 "o direction4 ,x is n[ g5]ally believ$ t ,x rays are waves 9 ! e!r set up by ! sudd5 /oppage ( ! ca?ode rays at ! plat9um anode4 ,illu/ration3 ,,fig4 #dbc4--;,an ,x ray tube4 #dba4 ,! ,electromagnetic ,!ory ( ,light4--,! /udy ( electric waves has %[n t !y are simil> to light waves 9 _m respects3 7a7 !y h ! same velocity2 7b7 !y c be reflect$ & refract$4 ,! ma9 diff]5ce is 9 _! l5g?1 light waves be+ v mu* %ort]4 ,9 #ahfd ,james ,cl]k ,maxwell1 an ,engli% physici/1 propos$ ! !ory t e!r waves c\ld be produc$ by electrical means & t light waves are electromagnetic4 ,9 #ahhh ,h]tz prov$ by 8 exp]im5ts t e!r waves hav+ ! same velocity z light c\ld be produc$ 9 ?is way4 ,x is n[ ! g5]al belief t light waves are e!r waves produc$ by ! vibrations ( ! electrons )9 ! atoms & t !y consi/ ( electromagnetic waves 9 ! e!r4 #dbb4 ,radio-activity4--,9 #ahif ,h5ri ,becqu]el ( ,p>is discov]$ t uranium & its comp\nds emit a =m ( radiation t produces an effect ^u a photographic plate t is simil> to t result+ f ! action ( ,x rays4 ,^! rays are (t5 call$ ,becqu]el rays 9 honor ( _! discov]]4 ,! prop]ty ( emitt+ su* rays is call$ radio-activity1 & ! sub/ances produc+ !m are call$ radio-active4 ,9 #ahih1 ,pr(essor & ,mme4 ,curie aft] an inve/igation ( all ! elem5ts f\nd t ?orium1 "o ( ! *ief con/itu5ts ( inc&esc5t gas mantles1 toge!r ) its comp\nds1 0 also radio-active4 ,?is may be %[n by ! foll[+ exp]im5t3 ,place a flatt5$ gas mantle ^u a photographic plate & leave 9 a light tight-box = sev]al days4 ,^u develop+ ! plate 9 ! usual way a di/9ct image ( ! mantle w be f\nd ^u ! plate4 #dbc4 ,radium4--,mme4 ,curie discov]$ also t pit*-bl5de possess$ mu* great] radio-active p[] ?an ei!r ?orium or uranium4 ,aft] prolong$ *emical exp]im5ts %e obta9$ f sev]al tons ( ! ore a few milligrams ( a sub/ance m ?an a million times z active z ?orium or uranium4 ,%e call$ ?is new sub/ance radium4 ,radium is cont9ually be+ decompos$1 ?is decomposition be+ accompani$ by ! production ( a great deal ( heat4 ,x has be5 calculat$ t x w take ab\t #cjj ye>s = a p>ticle ( radium to be entirely decompos$ & sep>at$ into o!r sub/ances4 ,x is also believ$ t radium itself is ! product ( ! decomposition ( uranium1 atomic weight #bch1 & t ! f9al product ( successive decompositions may be "s in]t metal1 l lead1 atomic weight #bjg4 ,! radiation giv5 (f by radio-active sub/ances consi/s ( ?ree k9ds3 7,a7 ,positively *>g$ p>ticles ( helium call$ alpha rays3 7,b7 negatively *>g$ p>ticles call$ beta rays3 7,c7 gamma rays4 ,! alpha rays h little p5etrat+ p[]1 a %eet ( pap] or a %eet ( alum9um #j4je mm4 /opp+ !m4 ,^u los+ _! *>ges !y become atoms ( helium4 ,_! velocity is ab\t #a_/aj ( t ( light or #ah1jjj miles a second4 ,! sp9?>iscope is a little in/rum5t devis$ by ,sir ,williams ,crookes 9 #aijc to %[ direct evid5ce t p>ticles are cont9ually be+ %ot (f f radium4 ,9 ?is in/rum5t 7,fig4 #dbd71 a speck ( radium ,r is plac$ on ! "u side ( a wire plac$ a few millimet]s above a scre5 ,s cov]$ ) cry/als ( z9c sulphide4 ,look+ 9 ! d>k at ?is scre5 ?r\gh ! l5s ,l1 a cont9u\s succession ( sp>ks is se5 l a sw>m ( fireflies on a w>m summ] night4 ,ea* fla% is due to an alpha p>ticle /rik+ ! scre54 ,! beta rays are suppos$ to be ca?ode rays or electrons ) velocities ( f #dj1jjj to #agj1jjj miles a second4 ,! gamma rays are suppos$ to be ,x rays produc$ by ! beta rays /rik+ solid objects4 ,illu/ration3 ,,fig4 #dbd4--;,a sp9?>iscope4 #dbd4 ,! discov]y ( radio-activity has revolutioniz$ ! ideas ( ! con/itution ( matt]4 ,fur!r1 ! results ( exp]im5ts ^u radio-active mat]ials reveals ! pres5ce ( imm5se quantities ( sub-atomic en]gy4 ,if man ev] discov]s a means ( utiliz+ ?is1 he w ent] a /oreh\se ( en]gy ( f> great] ext5t & value ?an any ( :i* he has z yet made use4 ,a consid]ation ( ?is unexplor$ region gives ze/ to ! "w ( ^? :o day by day are /riv+ to und]/& & control =ces ( nature4 ,important ,topics #a4 ,oscillatory nature ( dis*>ge ( ,leyd5 j>4 ,pro(s4 #b4 ,wireless telegraphy & telephony4 #c4 ,electrical dis*>ges 9 r>efi$ gases4 #d4 ,ca?ode & ,x rays4 #e4 ,electromagnetic !ory ( light4 #f4 ,radio activity & radium4 ,illu/ration3 ,,cont95tal ,,telegraph ,,code ,a 4 - ,j 4 - - - ,s 4 4 4 ,b - 4 4 4 ,k - 4 - ,t - ,c - 4 - 4 ,l 4 - 4 4 ,u 4 4 - ,d - 4 4 ,m - - ,v 4 4 4 - ,e 4 ,n - 4 ,w 4 - - ,f 4 4 - 4 ,o - - - ,x - 4 4 - ,g - - 4 ,p 4- - 4 ,y - 4 - - ,h 4 4 4 4 ,q - - 4 - ,z - - 4 4 ,i 4 4 ,r 4 - 4 ,,p]iod ,,int]rogation ,,exclamation 4 4 4 4 4 4 4 4 - - 4 4 - - 4 4 - - #a 4 - - - - #b 4 4 - - - #c 4 4 4 - - #d 4 4 4 4 - #e 4 4 4 4 4 #f - 4 4 4 4 #g - - 4 4 4 #h - - - 4 4 #i - - - - 4 #j - - - - - ,,*apt] ,,xviii ,,wireless ,,telephony ,,& ,,alt]nat+ ,,curr5ts ,! developm5ts 9 wireless communication h be5 s rapid dur+ rec5t ye>s t a m ext5d$ acc\nt1 ?an t giv5 9 ,art4 #dag ( ! app>atus & me?ods us$ at ! pres5t "t1 seems desirable4 ,! /udy ( ,alt]nat+ ,curr5ts is also includ$ ) ! idea t x w make ! text m complete & ( wid] usefulness4 ,,wireless ,,telephony #dbe4 ,! ,wireless ,telephone4--,"o ( ! mo/ important developm5ts 9 wireless communication 9 rec5t ye>s has be5 9 wireless telephony4 ,we realize its possibilities1 :5 we he> ( ! a*ievem5ts ( talk+ across an ocean or betwe5 airplanes & ! gr\nd4 ,! wireless telephone c be be/ und]/ood by comp>+ x ) ! common telephone4 ,:5 ! latt] is 9 use1 a direct curr5t fl[s cont9ually ?r\gh ! in/rum5t4 7,see ,arts4 #cab-caf47 ,:5 a p]son speaks into ! transmitt]1 ! s\nd waves ( ! voice cause ! diaphragm to vibrate1 ?is action causes rapid *anges 9 ! resi/ance ( ! transmitt]1 :i* 9 turn causes ! direct curr5t to fluctuate j 9 /ep ) ! pulses ( ! voice waves4 ,?is fluctuat+ direct curr5t passes ?r\gh ! prim>y ( an induction coil1 produc+ 9 ! second>y an int5sifi$ alt]nat+ curr5t4 ,?is passes ov] ! l9e wires to ! receiv] :]e x produces v>iations 9 ! magnetic field affect+ ! receiv] diaphragm1 caus+ ! latt] to reproduce ! voice ( ! p]son speak+ 9 ! transmitt]4 ,n[ to make ! comp>ison cle>1 two facts mu/ be not$ ) reg>d to ! wire telephone3 fir/1 !re mu/ be an action 9 ! transmitt] :i* causes v>iations 9 a curr5t ?r\gh ! in/rum5t2 second1 ?is fluctuat+ curr5t produces a m int5se alt]nat+ curr5t :i* fl[s ov] ! l9e & affects ! receiv] diaphragm1 produc+ !re s\nd vibrations ( great] int5sity ?an ^? us$ at ! transmitt]4 ,?is add$ en]gy comes f ! curr5t fl[+ ?r\gh ! transmitt]4 ,! case is analog\s to t ( an electric bell4 ,! armature ( ! bell vibrates ) great] en]gy ?an is requir$ to pu% ! button1 ! extra en]gy be+ d]iv$ f ! batt]y4 #dbf4 ,! ,action ( ! ,wireless ,telephone4--,9 ! wireless telephone we h a cont9u\s /ream ( electric waves ( high frequ5cy4 7,see ,fig4 #dbe;,a47 ,?is /ream ( electric waves corresponds to ! curr5t t fl[s ?r\gh ! transmitt] 9 ! wire telephone4 ,^! waves are ( su* high frequ5cy t ev5 ?\gh we _h a receiv] diaphragm vibrat+ 9 /ep ) ! waves1 we c\ld n he> ! s\nd because ! human e> _c he> a s\nd :i* consi/s ( m ?an ab\t #dj1jjj vibrations p] second4 ,! s\nd waves act ^u ?is /ream ( waves v mu*1 z 9 ! wire telephone1 ! transmitt] acts to modify ! l9e curr5t4 ,! impulses caus$ by ! voice are mu* sl[] ?an ! electric waves fir/ m5tion$ & ^! sl[] impulses are reproduc$ 9 ! receiv]4 ,n only are ^! sl[] impulses reproduc$ b !y are amplifi$1 t is1 produc$ ) great] en]gy ?an ! impulses impress$ on ! /ream ( waves4 ,fig4 #dbe;,a repres5ts z ne>ly z is possible 9 a diagram ! cont9u\s /ream ( electric waves4 ,fig4 #dbf;,b1 repres5ts ! impulses produc$ by ! s\nd alone1 & ,fig4 #dbf;,c1 %[s h[ ^! voice impulses are impress$ on ! /ream ( waves4 ,illu/ration3 ,,fig4 #dbe4--;,a1 unmodifi$ high frequ5cy waves2 ,b1 waves ( voice frequ5cy2 ,c1 high frequ5cy waves modifi$ by waves ( voice frequ5cy4 ,illu/ration3 ,,fig4 #dbf4--,vacuum tube1 transmitt+ type4 7,we/]n ,electric ,co47 ,illu/ration3 ,,fig4 #dbg4--,vacuum tube1 receiv+ type4 7,we/]n ,electric ,co47 ,illu/ration3 ,,fig4 #dbh4--;,diagram ( wireless telephone transmitt+ set4 #dbg4 ,! ,vacuum ,tube or ,audion4--,! device by :i* all ( ?is is accompli%$ is ! vacuum tube4 7,see ,fig4 #dbf47 ,?is tube conta9s ?ree electrodes4 ,fir/1 a filam5t 7,f1 9 ,fig4 #dbh7 :i* is heat$ by a curr5t f a batt]y 7,b#a1 ,fig4 #dbh7 & because x is heat$1 s5ds out a /ream ( electrons4 ,second1 ! plate :i* =ms ! anode ( ! circuit f batt]y1 ,b#b4 ,?is plate receives ! electrons :i* are ?r[n (f by ! heat$ filam5t1 h5ce a curr5t fl[s ?r\gh ! circuit ( ,b#b2 ! dis*>ge ?r\gh ! tube dep5d+ on ! e4m4f4 betwe5 ! filam5t & ! plate4 ,?ird1 a grid is plac$ betwe5 ! filam5t & ! plate & is connect$ to ! second>y ( ! induction coil1 ! prim>y ( :i* is connect$ to ! transmitt]4 ,:5 ! transmitt] diaphragm is vibrat+1 ! e4m4f4 induc$ 9 ! second>y ( ! induction coil causes a v>iation 9 ! pot5tial ( ! grid4 ,?is means a v>iation 9 ! electric field betwe5 ! filam5t & ! plate4 7,see ,fig4 #dbh47 ,! *ang+ electric field causes a v>iation 9 ! dis*>ge ( electrons ?r\gh ! tube2 ! v>iation corresponds to ! vibrations ( ! transmitt] diaphragm4 ,?is produces a surg+ curr5t ( ! frequ5cy ( ! s\nd waves 9 ! prim>y ( ! trans=m] 7,t1 ,fig4 #dbh74 ,! second>y ( ?is trans=m] is connect$ to ! ant5n 7,a7 & ! e>? 7,e74 ,by means ( ! trans=m]1 rapid surg+s are set up 9 ! ant5n & ^! surg+s produce a cont9u\s /ream ( electromagnetic waves :i* goes out 9 space4 7,l ,fig4 #dbf;,c47 ,^! electromagnetic waves produce oscillations 9 ! ant5n ( a receiv+ /ation4 ,! ant5n transmit ! impulses to a tube 7,fig4 #dbg7 :i* acts z a detector1 & makes possible ! reproduction ( ! s\nd by an ord9>y telephone receiv]4 ,illu/ration3 ,,fig4 #dbi4--,view ( wireless telephone set4 ,! vacuum tube 9 ! transmitt+ circuit also amplifies ! impulses1 t is1 ! en]gy ( ! waves giv5 out is great] ?an t ( ! impulses :i* produce !m1 ! additional en]gy be+ d]iv$ f ! batt]y s5d+ curr5t ?r\gh ! plate & filam5t4 ,9 op]ation1 ! filam5t & ! plate are connect$ to a batt]y ) a cond5s] 7,,vc7 & an inductance coil 7,i7 9 ! circuit1 z %[n 9 ,fig4 #dbh4 ,photograph ( a complete mod]n wireless telephone set is %[n 9 ,fig4 #dbi4 ,,alt]nat+ ,,curr5ts #dbh4 ,alt]nat+ curr5ts are ( int]e/ to u because ( _! g5]al comm]cial use4 ,to und]/& ! reason = ! ext5sive application ( alt]nat+ curr5ts x is necess>y to le>n ! fundam5tal pr9ciples :i* p]ta9 to !m4 ,! production ( su* curr5ts has already be5 expla9$ 9 ,arts4 #cjj-cjd4 ,x %\ld be rememb]$ t ! curr5t develop$ 9 ! armature ( a dynamo is alt]nat+4 ,a dynamo may deliv] a direct or an alt]nat+ curr5t1 dep5d+ on ! me?od ( collect+ ! curr5t f ! armature4 ,if a commutator is us$1 ! ma*9e deliv]s direct curr5t1 if slip r+s are employ$1 an alt]nat+ curr5t is deliv]$4 #dbi4 ,! ,magnetic ,field ( an ,alt]nat+ ,curr5t4--,! magnetic field ( a direct curr5t has be5 consid]$ 9 ,arts4 #bee-bef4 ,x has be5 %[n to be arrang$ 9 circles ab\t ! conductor1 accord+ to ! ,"r ,h& ,rule4 7,see ,figs4 #bbi & #bcj47 ,^! facts w help "o to und]/& ! foll[+ exp]im5t3 ,if a numb] ( magnetic compasses be arrang$ 9 a circle ab\t a /raight v]tical wire c>ry+ a direct curr5t1 ! compass ne$les w po9t out a circle ab\t ! wire4 7,see ,fig4 #dcj1 ,a47 ,if n[ ! curr5t be rev]s$ ! compass ne$les w rev]se !mselves & po9t 9 a direction j opposite to t tak5 at fir/4 7,see ,fig4 #dcj1 ,b47 ,?is w be cle> if y imag9e y\rself walk+ ar\nd ! wire 9 ! direction ! compass ne$les po9t$ at fir/1 & !n walk+ ar\nd ! wire 9 ! rev]se direction4 ,?is illu/rates :at happ5s 9 ! field ( an alt]nat+ curr5t4 ,! field rev]ses ea* "t ! curr5t rev]ses4 ,! magnetic field ( an alt]nat+ curr5t n only rapidly rev]ses itself1 b also cont9ually *anges 9 int5sity4 ,at ! in/ant :5 ! curr5t rev]ses1 ! =ce ( ! magnetic field is z]o s9ce ! curr5t at t in/ant is z]o4 ,z ! curr5t beg9s fl[+ & increases to its maximum int5sity1 ! magnetic field appe>s & increases 9 int5sity2 & z ! curr5t decreases to z]o1 ! magnetic field *anges 9 a simil> mann]4 ,! field z x gr[s 9 /r5g? ext5ds f>!r & f>!r f ! wire1 z x decreases 9 /r5g? x contracts or draws clos] to ! wire4 ,?us ! magnetic field may be said to exp& & contract4 ,we may picture ! l9es ( =ce z cont9ually mov+4 ,9 a typical a4-c4 circuit1 ! complete s]ies ( *anges takes place 9 a small fraction ( a second1 & is repeat$ _m times ov] 9 a second4 ,contra/ ?is ) ! magnetic field ( a con/ant direct curr5t4 ,"h ! magnetic field has ! same direction z long z ! curr5t fl[s & does n *ange 9 /r5g?4 ,?is comp>ison is important because mo/ ( ! diff]5ces betwe5 direct & alt]nat+ curr5ts dep5d on diff]5ces 9 ! action ( _! magnetic fields4 ,illu/ration3 ,,fig4 #dcj4--;,arrangem5t ( compasses ab\t a wire c>ry+ an alt]nat+ curr5t4 #dcj4 ,trans=m]s4--,! trans=m] has be5 describ$ 9 ,arts4 #cji-caj4 ,! pr9ciple ( ! trans=m] may be illu/rat$ by ! foll[+ exp]im5t3 ,a coil hav+ sev]al hundr$ turns ( ,no4 #ah d4c4c4 copp] wire is plac$ ov] "o arm ( a ,u %ap$ iron core 7see ,fig4 #dca7 & !n connect$ to a #aaj volt a4-c4 light+ circuit4 ,ano!r coil 7,s7 hav+ ab\t #ej turns ( ,no4 #bb d4c4c4 copp] wire is connect$ to an electric bell or buzz]1 or a l[ voltage electric light bulb4 ,:5 ! small coil is held ov] ! o!r arm ( ! ,u %ap$ iron core1 ! bell r+s or ! bulb gl[s4 ,x is evid5t t ! electromotive =ce develop$ 9 ! small coil 7,s7 is due to ! alt]nat+ magnetic field surg+ back & =? ?r\gh ! iron core4 ,9 ,fig4 #dca ! core is op5 s9ce ! magnetic field mu/ pass ?r\gh ! air f "o end ( ! core to ! o!r4 ,a typical trans=m] has a clos$ core to provide a clos$ magnetic circuit4 ,to secure ?is1 take a suitable b> ( iron & lay across ! end ( ! ,u %ap$ core1 & notice any *ange 9 ! induc$ curr5t produc$ 9 ! small coil1 due to increas$ movem5t ( magnetism ?r\gh ! clos$ iron core4 ,illu/ration3 ,,fig4 #dca4--;,diagram ( a trans=m]4 ,?is exp]im5t illu/rates ! con/ruction & action ( a trans=m]4 ,9 a comm]cial trans=m]1 ! two w9d+s are on a clos$ magnetic circuit4 7,see ,figs4 #cjd & #cje1 p4 #cdf47 ,to keep ! coils insulat$1 ! trans=m] is plac$ 9 an iron h\s+ & cov]$ ) oil4 ,^! h\s+s1 or trans=m] cases are g5]ally atta*$ to poles ne> build+s 9 :i* alt]nat+ curr5t is us$4 #dca4 ,voltage ,relation 9 a ,trans=m]4--,9 ! exp]im5t describ$ above1 a bell 0 rung by an induc$ curr5t produc$ 9 ! second>y coil4 ,! induc$ e4m4f4 0 less ?an ! voltage ( ! prim>y coil p>tly because !re 0 "s magnetic leakage1 b ma9ly because !re 7 few] turns ( wire on ! second>y4 ,9 a comm]cial trans=m] ! magnetic leakage is practically z]o4 ,9 su* a case1 ! ratio ( ! numb] ( turns on ! prim>y coil to ! numb] on ! second>y equals ! ratio ( ! e4m4f4 induc$ 9 ! prim>y to ! e4m4f4 induc$ 9 ! second>y4 ,suppose1 = example1 we wi% to make a bell r++ trans=m] to use on a #aaj volt light+ circuit1 #aj volts be+ requir$ = ! bell2 ! second>y w !n ne$ "o-elev5? ( ! numb] ( turns ( ! prim>y4 ,s t if #eej turns are on ! prim>y1 !n #ej turns w be ne$$ = ! second>y4 ,?is w be a /ep-d[n trans=m]4 ,on ! o!r h&1 suppose we wi% to /ep-up ! voltage z is done 9 a c]ta9 p[] /ation :]e ! voltage ( ! g5]ators is #fjjj volts1 ! voltage be+ /epp$ up to #dd1jjj by means ( l>ge trans=m]s4 ,?is means t ! second>y coils h approximately #g-a_/c times z _m turns z ! prim>y4 #dcb4 ,p[] ,loss 9 a ,trans=m]4--,:5 ! voltage is /epp$ up 9 a trans=m]1 d we ga9 p[]8 ,to answ] ?is "q we mu/ rememb] t electric p[] does n dep5d on voltage alone b on ! product ( e4m4f4 & curr5t int5sity4 7,see ,art4 #bia47 ,by te/s ) a4-c4 voltmet]s & ammet]s1 we f9d t :5 ! second>y e4m4f4 is great] ?an ! prim>y e4m4f41 ! second>y curr5t int5sity is less ?an t 9 ! prim>y4 ,x is also f\nd t ! p[] develop$ is less ?an ! p[] receiv$ by ! trans=m]1 i4e41 ! output is less ?an ! input z we w\ld expect f ! law ( ma*9es4 ,! p[] loss is ma9ly due to ! "w requir$ to rev]se ! magnetism1 t is1 to cont9ually rev]se ! position ( ! iron molecules4 7,see ,art4 #bje47 ,! en]gy lo/ 9 ?is mann] is kn[n z core loss s9ce x occurs 9 ! iron core4 ,! lo/ en]gy appe>s z heat4 ,s mu* heat is develop$ 9 l>ge trans=m]s t special means ( cool+ are provid$4 ,9 ord] to make ! heat develop$ z small z possible1 ! cores are lam9at$ 7see ,fig4 #cje1 p4 #cdf71 t is1 built up ( ?9 %eets ( iron1 because if ! iron cores 7 solid1 ! *ang+ magnetic fields w\ld induce electric curr5ts 9 ! iron cores1 :i* w\ld produce an excessive am\nt ( heat ) a correspond+ly l>ge p[] loss4 ,illu/ration3 ,,fig4 #dcb4--;,diagram ( bell-r++ trans=m]4 #dcc4 ,*oke ,coils & ,inductance4--,if we ref] to ,fig4 #dcb we see t ! prim>y w9d+ ( ! bell r++ trans=m] is connect$ across ! l9e4 ,?is w9d+ =ms a clos$ circuit :e!r ! bell is r++ or n4 ,! resi/ance ( ?is w9d+ is small4 ,let u assume x to be "o ohm4 ,) a "o ohm resi/ance connect$ across a #aaj volt l9e we might expect a curr5t ( #aaj amp]es4 ,?is is c]ta9ly :at we %\ld get if we 7 to connect a "o ohm resi/ance across a l9e hav+ #aaj volts direct4 ,! prim>y w\ld =m a %ort circuit if ! curr5t 7 direct4 ,b ! fact is t practically no curr5t fl[s ?r\gh ! prim>y w9d+ :5 ! bell is n r++4 ,h]e9 lies "o ( ! important diff]5ces betwe5 alt]nat+ & direct curr5ts4 ,) an alt]nat+ curr5t ! prim>y w9d+ ( our trans=m] acts z a *oke coil & *okes d[n ! curr5t almo/ to z]o4 ,let u see h[ ?is is done4 ,illu/ration3 ,,fig4 #dcc4--;,a circuit conta9+ a *oke coil4 ,let ,fig4 #dcc repres5t a *oke coil4 ,s9ce alt]nat+ curr5t is us$1 ! magnetic field is cont9ually *ang+4 ,ea* turn ( wire has its own magnetic field4 ,! l9es ( =ce ( turn numb] #a exp& & contract & z !y d s !y move across turns #b1 #c & s on4 ,9 l mann] ! l9es ( =ce f ea* turn ( wire move across ! o!r turns4 ,9 o!r words ! coil is cutt+ its own l9es ( =ce4 ,n[ :5ev] an electric conductor cuts magnetic l9es ( =ce an electromotive =ce is induc$ 9 ! conductor4 ,!re is !n an e4m4f4 induc$ 9 ! coil by its own magnetic field4 ,?is induc$ e4m4f4 on ! :ole opposes ! appli$ e4m4f42 9 ! prim>y ( our bell r++ trans=m] ! induc$ e4m4f4 opposes ! e4m4f4 ( ! l9e to su* an ext5t z to r$uce ! curr5t almo/ to z]o4 ,inductance is ! action ( an alt]nat+ curr5t 9 induc+ an oppos+ e4m4f4 9 ! coil 9 :i* ! curr5t is fl[+4 ,s9ce ?is oppos+ e4m4f4 is induc$ 9 ! coil by its own magnetic field ?is action is also call$ self-induction4 ,9 a trans=m] ! action ( ! field ( ! prim>y ^u ! second>y is mutual induction2 :ile ! action ( ! field ( ! prim>y 9 *ok+ ! curr5t 9 ! prim>y itself is self-induction or inductance4 ,a coil hav+ a s+le w9d+ & us$ to introduce inductance 9 a circuit is call$ a *oke coil4 ,a *oke coil ins]t$ 9 a lamp circuit 9 s]ies ) ! lamps dims ! lamps because x r$uces ! int5sity ( ! curr5t4 ,illu/ration3 ,,fig4 #dcd4--;,diagram %[+ graphically an alt]nat+ curr5t ) a lag ( #cj beh9d its electromotive =ce4 ,self-induction causes ! curr5t to lag1 t is1 ! curr5t does n q rea* its maximum at ! in/ant ! voltage rea*es its maximum4 ,fig4 #dcd %[s graphically an e4m4f4 & a lagg+ curr5t4 ,9 ?is figure ! maximum curr5t is %[n foll[+ ! maximum voltage at an int]val ( #cj degrees4 ,9 o!r words ! armature 9 a two-pole field mu/ turn #cj degrees f ! position ( maximum voltage be=e ! curr5t 9 ! coil1 :]e ! self-induction occurs1 rea*es its maximum4 #dcd4 ,reactance & ,imp$ance4--,a *oke coil has resi/ance z well z inductance4 ,its resi/ance c be f\nd by ! voltmet]-ammet] me?od1 us+ a direct curr5t4 7,see ,art4 #bgh47 ,let u take = example ! prim>y w9d+ ( a bell r++ trans=m]4 ,us+ a direct curr5t & te/+ ! coil ) a voltmet] & ammet] we f9d its resi/ance to be1 let u say1 "o ohm4 ,if we connect ! same coil across a #aaj volt a4-c4 l9e we f9d ! curr5t to be v small1 say #j4je amp]e4 ,! coil n[ has resi/ance & reactance4 ,reactance is ! effect ( self-induction 9 h9d]+ ! fl[ ( curr5t4 ,x is measur$ 9 ohms4 ,! comb9$ effect ( resi/ance & reactance is call$ imp$ance4 ,9 ! example above1 ! coil has #aaj 7volts7_/#j4je 7amp]e7 #bbjj ohms ( imp$ance4 ,9 apply+ ,ohm's law to an alt]nat+ curr5t circuit1 imp$ance mu/ be sub/itut$ = resi/ance4 ,ohm's law z appli$ to an a-c4 circuit %\ld be /at$3 ,curr5t int5sity equals e4m4f4 divid$ by imp$ance1 or ,i ,e_/,z4 7,z imp$ance47 ,illu/ration3 ,,fig4 #dce4--,! relation betwe5 resi/ance1 reactance & imp$ance4 ,imp$ance1 h[ev]1 does n equal ! sum ( resi/ance & reactance4 ,! relation betwe5 ^! ?ree quantities is simil> to t betwe5 ! ?ree sides ( a "r triangle1 9 :i* ! imp$ance repres5ts ! hypot5use1 & ! resi/ance & reactance ! o!r two sides4 ,see ,fig4 #dce :i* indicates t ,resi/ance ,reactance ,imp$ance1 or 7,r ,x ,z74 7,x reactance47 ,to illu/rate ?is relation2 suppose ! prim>y ( a trans=m] has #aj ohms imp$ance & #h ohms resi/ance1 !n ! reactance equals #aj - #h #f1 or ! reactance is #f ohms4 ,ex]cises #a4 ,f9d ! reactance ( a *oke coil hav+ a resi/ance ( #aj ohms1 :5 its imp$ance is #ej ohms4 ,h[ great a curr5t fl[s ?r\gh ?is coil if ! t]m9al voltage is #aaj volts8 #b4 ,:5 ! bell is r++1 ! prim>y ( a bell r++ trans=m] has an appreciable curr5t4 ,suppose ?is curr5t is #j4b amp]e4 ,:at is ! imp$ance if ! voltage ( ! l9e is #aae volts8 ,:at is ! reactance if ! resi/ance is #a ohm8 #c4 ,! prim>y ( a l>ge trans=m] has a t]m9al voltage ( #fjjj volts & a curr5t ( #fjj amp]es4 ,:at is ! imp$ance8 ,if ! resi/ance is #f ohms1 :at is ! reactance8 ,illu/ration3 ,,fig4 #dcf4--;,a telephone set %[+ a cond5s] us$ 9 ! circuit ( ! r+]4 #dce4--,! electric cond5s] 7see ,art4 #bca7 is a v useful device 9 a4-c4 circuits2 e4g41 9 telephone sets us$ 9 cities1 a cond5s] is us$ 9 ! r++ circuit1 z %[n 9 ,fig4 #dcf4 ,alt]nat+ curr5t is requir$ to r+ su* a bell & a cond5s] p]mits an a4-c4 curr5t to act ?r\gh x1 al?\gh x entirely prev5ts ! fl[ ( a direct curr5t4 ,?is peculi> action w n[ be expla9$4 #dcf4 ,! action ( a cond5s] 9 an alt]nat+ curr5t circuit may be illu/rat$ by ! foll[+ exp]im5t4 ,connect twelve1 #a m4f4 7micr(>ad7 cond5s]s1 9 p>allel1 & !n atta* !m to a #aaj volt a4-c4 l9e s t an inc&esc5t lamp is 9 circuit z %[n 9 ,fig4 #dcg4 ,! lamp w be f\nd to gl[ brightly1 al?\gh !re is no electrical connection betwe5 ! two sets ( cond5s] plates4 ,if ! same arrangem5t is connect$ to a #aaj volt direct curr5t circuit1 ! lamp does n gl[ because x is really an op5 circuit4 ,! lamp gl[s on an a4-c4 circuit because1 al?\gh no electricity fl[s ?r\gh ! cond5s]1 x does fl[ into & out ( ! cond5s]1 surg+ back & =? ?r\gh ! lamp ) suffici5t int5sity to cause x to gl[ brightly4 ,:5 ! a4-c4 curr5t moves "o way 9 ! circuit1 "o set ( plates ( ! cond5s]s becomes *>g$ positively1 ! o!r1 negatively4 ,:5 ! a4-c4 curr5t rev]ses1 ! *>ges on ! cond5s] plates rev]se4 ,9 ! ord9>y light+ circuit #abj rev]sals take place ea* second1 s t electricity rapidly fl[s into & out ( ! cond5s]s4 ,on remov+ "o cond5s] aft] ano!r f ! circuit1 ! lamp is f\nd to gl[ less & less1 till :5 b "o cond5s] is left1 no gl[+ is obs]v$1 s9ce "o small cond5s] does n h suffici5t capacity4 ,illu/ration3 ,,fig4 #dcg4--,twelve cond5s]s 9 circuit ) an inc&esc5t lamp4 ,! unit ( capacity is ! ,f>ad4 ,capacity is def9$ z ! quantity ( electricity p] second t fl[s into a cond5s] :5 ! voltage at ! t]m9als *anges at ! rate ( "o volt p] second4 ,if a *ange ( "o volt p] second causes "o c\lomb to fl[ p] second1 t is1 a curr5t ( "o amp]e1 ! capacity is "o f>ad4 ,! cond5s]s us$ 9 ! above exp]im5t h a capacity ( "o micr(>ad1 or "o million? ( a f>ad4 ,a cond5s]1 on acc\nt ( its capacity1 causes an a4-c4 curr5t to lead ! voltage1 t is ! curr5t rea*es its maximum value be=e ! voltage does4 ,9 ?is respect a cond5s] has an effect opposite to t ( ! self-induction ( a *oke coil 7! latt] caus+ ! curr5t to lag74 7,see ,fig4 #dce47 #dcg4 ,transmission ( ,electric ,p[]4--,a field ( peculi> usefulness = a4-c4 curr5ts is 9 ! economical transmission ( electric p[]4 ,?is fact is due to ! foll[+ reasons3 7a7 ,! loss ( electrical p[] 9 a transmission l9e is due to ! production ( heat2 ! heat produc$ be+ proportional to ,i,r1 or to ! squ>e ( ! curr5t int5sity4 ,any less5+ ( ! curr5t fl[ requir$ to transmit a giv5 p[] w !re=e increase ! effici5cy ( transmission4 7b7 ,9 ord] to employ a small curr5t 9 transmitt+ a l>ge am\nt ( p[]1 we mu/ use a v high e4m4f4 ,su* high electromotive =ces1 say f #fj1jjj to #ajj1jjj volts1 c be obta9$ only by ! use ( a4-c4 trans=m]s1 s9ce x is n practicable to build a direct curr5t g5]ator capable ( produc+ #fj1jjj volts4 ,9 l>ge p[] transmission sy/ems1 a4-c4 g5]ators are us$ to produce p[]ful alt]nat+ curr5ts4 ,! e4m4f4 is !n /epp$ up to a suitable voltage 7#bcjj-ajj1jjj7 by trans=m]s & s5t ov] transmission l9es to ! v>i\s places :]e ! p[] is to be us$2 at ^! places suitable trans=m]s /ep-d[n ! e4m4f4 to a conv5i5t or safe voltage = use4 7,see ,fig4 #ddb ( a transmission l9e & ,fig4 #dch ( a l>ge p[] transmission sy/em1 & ,fig4 #dci ( an a4-c4 g5]ator & p[] plant47 ,illu/ration3 ,,fig4 #dch4--;,diagram ( an alt]nat+ curr5t high t5sion p[] sy/em4 7,a7 ,alt]nator1 7,tu7 wat] turb9e1 direct connect$ to alt]nator1 7,e7 excit]1 7,t#a7 /ep-up trans=m]s 9 p[] /ation1 7,t#b7 /ep-d[n trans=m]s 9 sub/ation1 7,m7 motor1 7,l7 lamps1 s+le-phase1 ?ree-wire sy/em1 7,t#c7 /ep-d[n trans=m]s deliv]+ ?ree-phase curr5t to rot>y conv]t] 7,r7 :i* deliv]s direct curr5t to ! trolley l9e4 #dch4 ,p[] ,factor4--,! p[] factor is a matt] ( int]e/ & importance 9 ! use ( a4-c4 ma*9es4 ,its mean+ & use may be le>n$ f ! foll[+ explanation3 ,9 a direct curr5t circuit1 watts equals volts times amp]es4 ,9 an alt]nat+ curr5t circuit1 ?is equation is true only :5 ! curr5t is 9 /ep ) ! voltage1 t is1 only :5 !re is no inductance or capacity 9 ! circuit4 ,if curr5t & voltage are out ( /ep1 i4e41 if !re is lag or lead 7see ,fig4 #dcd71 ! product ( volts & amp]es gives only ! app>5t p[]1 ! ratio betwe5 true & app>5t p[] dep5d+ on ! am\nt ( lag or lead4 ,?is ratio is call$ ! p[] factor4 ,9 an a4-c4 circuit1 !n1 ! p[] equation is3 watts volts amp]es p[] factor1 or p[] factor true p[]_/app>5t p[]4 ,! product ( volts & amp]es is ! app>5t p[] & is call$ volt-amp]es 9 di/9ction f ! true p[] or watts4 ,!re=e ! foll[+ is true3 p[] factor true watts_/volt-amp]es4 ,illu/ration3 ,,fig4 #dci4--,p[] h\se %[+ alt]nators1 direct connect$ to horizontal hydraulic turb9es4 ,note ! direct curr5t excit] on end ( %aft ( alt]nator4 7,c\rtesy ( ,g5]al ,electric ,co47 #dci4 ,s+le-phase ,curr5ts4--,!re are sev]al k9ds ( a4-c4 curr5ts4 ,"o ( ! mo/ common is ! s+le-phase4 ,x is simply ! common a4-c4 curr5t us$ = light & p[] 9 ! av]age home1 & uses a two-wire circuit ar\nd :i* ! curr5t is rapidly alt]nat+4 ,fig4 #ddj illu/rates ! *anges ( e4m4f4 9 an a4-c4 s+le-phase curr5t4 ,x may be produc$ by a s+le coil rotat+ 9 a magnetic field4 ,! curve ( ,fig4 #ddj repres5ts "o cycle1 t is1 "o complete s]ies ( *anges 9 ! electromotive =ces4 ,at ! end ( ! cycle ! armature is 9 ! same condition z at ! beg9n+ s f> z ! magnetic field is conc]n$4 ,x !n beg9s a new cycle4 ,! ord9>y comm]cial alt]nat+ curr5t has a frequ5cy ( #fj1 t is #fj cycles p] second4 ,"o rotation produces z _m cycles z !re are pairs ( poles4 ,= example1 if !re are #dh poles 9 ! g5]ator field1 "o rotation produces #bd cycles4 ,illu/ration3 ,,fig4 #ddj4--;,graph %[+ ! e4m4f4 *anges ( a s+le-phase curr5t = "o cycle4 #ddj4 ,?ree-phase ,curr5ts4--,n[ suppose we h ?ree coils z 9 ,fig4 #dda1 ! coils be+ ev5ly spac$1 or #abj degrees ap>t1 at ,a1 ,b1 & ,c4 ,if ! coils are rotat$ 9 a magnetic field1 ea* w produce an electromotive =ce4 ,! result produc$ by ?ree su* coils is call$ a ?ree-phase curr5t4 ,ord9>ily six wires1 or ?ree circuits1 w\ld be requir$ to c>ry ! curr5t produc$ by ?ree sep>ate coils2 = :5 coil ,c is 9 ! #ij degree position1 :]e its e4m4f4 is a maximum1 coil ,b is #abj degrees pa/ its maximum1 & coil ,a is #bdj degrees pa/ its maximum4 ,! graph 7,fig4 #dda7 %[s ! maximum po9ts ( ! ?ree e4m4f's4 sep>at$ by int]vals ( #abj degrees4 ,9 practice1 h[ev]1 x is f\nd possible to use ?ree wires in/ead ( six1 z expla9$ 9 ,art4 #dda4 ,illu/ration3 ,,fig4 #dda4--;,graph %[+ ! e4m4f4 *anges ( a ?ree-phase curr5t = "o cycle4 #dda4 ,?ree-wire ,transmission4--,! curr5ts produc$ 9 ! ?ree coils j describ$ und]go precisely ! same *anges z ^? repres5t$ 9 ! graph 7,fig4 #dda7 = ! ?ree electromotive =ces4 ,c>eful exam9ation ( ! graph w %[ t at any po9t ! sum ( ! plus e4m4f's4 equals ! sum ( ! m9us e4m4f's4 ,9 o!r words ! algebraic sum ( ! ?ree e4m4f's4 is z]o4 ,!re=e if we prop]ly connect a transmission l9e ( ?ree wires to ! g5]ator1 ! sum ( ! curr5ts leav+ ! g5]ator w equal ! sum ( ! curr5ts return+ to x4 ,s9ce ! algebraic sum ( ! curr5ts produc$ by ! ?ree coil comb9ation describ$ 9 ,art4 #ddj is always z]o1 x is possible to use ?ree wires on ?ree-phase transmission l9es4 ,fig4 #ddb %[s a t[] c>ry+ ?ree1 ?ree-wire transmission l9es4 ,long di/ance1 high t5sion transmission l9es are g5]ally ?ree-wire l9es c>ry+ ?ree-phase a4-c4 curr5ts4 ,illu/ration3 ,,fig4 #ddb4--;,a t[] support+ ?ree1 ?ree-phase circuits ( a high t5sion transmission l9e4 #ddb4 ,alt]nators4--,a dynamo :i* deliv]s alt]nat+ curr5t is kn[n z an alt]nator4 ,comm]cial alt]nators h _m pairs ( poles 9 ! field & z a rule ! field rotates :ile ! armature is /ation>y4 ,! field mu/ be suppli$ ) direct curr5t = ! pol>ity ( ea* coil 9 ! field mu/ rema9 un*ang$4 ,usually a sep>ate excit] is us$1 :i* is a small direct curr5t g5]ator4 ,! curr5t f ?is excit] is f$ into ! rotat+ field by means ( slip r+s4 ,fig4 #dci %[s a d4-c4 7direct curr5t7 excit] on ! end ( ! armature %aft ( ! l>ge alt]nator4 ,illu/ration3 ,,fig4 #ddc4--;,diagram ( a ,s]ies ,motor4 #ddc4 ,! ,a4-,c4 ,s]ies ,motors4--,! only type ( motor t w run on ei!r alt]nat+ or direct curr5t is ! s]ies motor4 ,! univ]sal motor us$ 9 h\sehold appliances su* z electric fans1 vacuum clean]s1 etc41 is a s]ies motor4 ,! reason a s]ies motor w run on ei!r direct or alt]nat+ curr5t is because ! direction ( rotation ( ! armature ( a motor dep5ds on 7a7 ! direction ( ! curr5t 9 ! armature1 & 7b7 ! pol>ity ( ! field4 ,rev]s+ ei!r ( ^! alone1 rev]ses ! direction ( rotation ( ! armature1 :ile rev]s+ bo? at ! same in/ant leaves ! direction ( rotation un*ang$4 ,fig4 #ddc is a diagram ( a s]ies motor s9ce ! field coils & armature are connect$ 9 s]ies4 ,on an a4-c4 l9e1 bo? field & armature curr5t mu/ !re=e rev]se at ! same in/ant4 ,9 a %unt motor 7simil> to ,fig4 #bhf7 we h a divid$ circuit1 & ! great] self-induction ( ! field coils causes an a4-c4 curr5t ?r\gh ^! coils to lag beh9d t fl[+ 9 ! armature s t ! two curr5ts d n rev]se at ! same in/ant4 ,illu/ration3 ,,fig4 #ddd4--;,diagram ( a gramme r+4 ,x is %[n connect$ to a s+le-phase curr5t s z to produce a rotat+ magnetic field1 simil> to t obta9$ ) a ?ree-phase curr5t4 7,ahr5s1 ,h>ley & ,burns47 ,illu/ration3 ,,fig4 #dde4--,! /ator ( an induction motor4 #ddd4 ,! ,induction ,motor4--,ano!r common type ( a4-c4 motor is ! induction motor4 ,its advantage lies 9 its simplicity4 ,x has nei!r commutator nor bru%es1 ! armature hav+ no connection ) an ext]nal circuit4 ,if ! wires ( a ?ree-phase l9e be connect$ to a coil w\nd 9 ! =m ( a gramme r+1 ! connections be+ #abj degrees ap>t z 9 ,fig4 #ddd1 ! magnetic field )9 ?is coil w *ange 9 ! same mann] z if a magnet 7 sp9n+ ^u a pivot at ! c5t] ( ! coil4 ,suppose ! ,n pole at "o in/ant is at ,a1 9 "o-?ird ( a cycle x moves to ,b1 9 ano!r ?ird to ,c1 & 9 "o cycle x makes a complete revolution4 ,?us we h a rotat+ magnetic field4 ,if a cup ( "s non-magnetic metal su* z alum9ium or copp] be plac$ on a pivot 9 ! c5t] ( ?is coil1 ! cup is cut by ! mov+ l9es ( =ce & curr5ts are induc$ 9 x4 ,because ( ^! curr5ts1 ! cup has a magnetic field ( its own1 & ! action ( ! two magnetic fields is su* z to pull ! cup ar\nd & cause x to rotate 9 ! same direction z t 9 :i* ! field ( ! coil rotates4 ,! coil repres5ts ! /ation>y "p1 ! /ator 7,fig4 #dde7 & ! cup ! rotat+ "p1 ! rotor1 ( an induction motor4 ,:ile ! cup rotates 9 ! same direction1 x does n rotate s rapidly z ! magnetic field4 ,if x %\ld x is pla9 t x w\ld n cut ! l9es ( =ce4 ,! diff]5ce betwe5 ! rate ( rotation ( ! rotor & t ( ! magnetic field is call$ ! slip4 ,! rotat+ "p 9 small induction motors is frequ5tly made 9 a s+le ca/+4 ,9 l>ge motors1 x is built up ( heavy copp] b>s4 ,?us1 f its appe>ance ! common =m ( rotor is kn[n z ! squirrel cage rotor4 7,see ,fig4 #ddf47 ,illu/ration3 ,,fig4 #ddf4--,! rotor ( an induction motor4 ,illu/ration3 ,,fig4 #ddg4--;,diagram illu/rat+ ! pr9ciple ( ! syn*ron\s motor4 ,! armature coil passes ! position %[n 9 ! figure at ! in/ant ! curr5t 9 ! l9e rev]ses4 ,?us ! armature keeps ) ! l9e curr5t1 mak+ "o revolution ) ea* cycle4 #dde4 ,a syn*ron\s motor is "o t keeps /ep ) ! alt]ations ( an alt]nat+ curr5t4 ,! l9e curr5t is f$ into ! armature by means ( two slip r+s & bru%es4 ,! pr9ciple ( ! syn*ron\s motor is illu/rat$ 9 ,fig4 #ddg4 ,?is %[s a motor hav+ a two-pole field4 ,! armature curr5t mu/ be rev]s$ twice 9 ea* revolution4 ,! rev]sal mu/ take place :5 ! armature w9d+ is p]p5dicul> to ! l9es ( =ce ( ! field4 ,9 a direct curr5t motor ?is rev]sal is br\ght ab\t by ! commutator4 ,9 a syn*ron\s motor ! armature rea*es ! #ij degree position at ! exact in/ant at :i* ! curr5t rev]ses 9 ! l9e4 ,?us 9 ! case ( a two-pole motor ! armature mu/ make exactly "o revolution = ea* cycle2 x is1 !re=e1 a con/ant spe$ motor4 ,su* motors are frequ5tly employ$ 9 conv]t] /ations :]e alt]nat+ curr5t is conv]t$ into direct curr5t by :at are call$ rot>y conv]t]s4 ,9 practice ! syn*ron\s motor has a numb] ( pairs ( field poles4 ,x is ess5tially an alt]nat+ curr5t g5]ator runn+ z a motor4 ,"o ( ! pr9cipal uses ( ! syn*ron\s motor is t ( a conv]t]1 receiv+ alt]nat+ curr5t & deliv]+ direct curr5t4 ,syn*ron\s motors are also us$ 9 transmission l9es to aid 9 ma9ta9+ con/ant voltage4 ,important ,topics ,! wireless telephone1 ess5tial p>ts1 action1 arrangem5t4 ,alt]nat+ curr5ts1 alt]nat+ fields4 ,trans=m]s1 voltage relation ( coils1 p[] & core losses4 ,self-induction1 inductance1 & coke coils1 uses1 applications4 ,imp$ance1 reactance1 & resi/ance2 relation & effects4 ,cond5s]s1 uses & applications ) a-c4 circuits4 ,alt]nat+ curr5t p[] transmission2 uses1 advantages4 ,p[] factor1 lag1 lead1 volt-amp]es1 true watts4 ,s+le- & ?ree-phase curr5ts2 uses & nature ( ea*4 ,?ree-wire transmission sy/ems1 alt]nators1 con/ruction1 & action4 ,a-c4 motors1 s]ies1 induction1 syn*ron\s4 ,,index ,ab]ration1 sph]ical1 #djh ,absolute scale ( temp]ature1 #afd ,absorptions ( gases by solids & liquids1 #bi ,accel]at$ motion1 #hf ,accel]ation1 #hg ,adhesion1 #ba ,a]oplane1 #ig ,air1 aspirator1 #fg brake1 #gd cu%ion1 #df height 7( atmosph]e71 #fd pressure1 #ef pump1 #ff weight1 #ef ,alt]nators1 #dha ,alt]nat+ curr5t1 #ccg1 #dff ,amalgamation1 #bgc ,ammet]1 #bia ,amp]e1 #bia ,ar*im$es' pr9ciple1 #dh ,arc light1 #cba ,armature1 #cce ,artesian wells1 #dd ,audion1 #dfc ,aurora borealis1 #dec ,balloon1 #gb ,b>omet]1 #ei ,beats1 #cgf ,boil+1 laws1 #bjh po9t1 #bjg ,boyle's ,law1 #fc ,breezes1 l& & sea1 #aha ,briti% !rmal unit1 #afb ,br[nian movem5ts1 #af ,calorie1 def9$1 #afb ,cam]a1 #dbf ,c&lep[]1 #cid ,capill>y action1 #be ,c>tesian div]1 #ga ,ca?ode rays1 #dec ,c5trifugal =ce1 #ia ,*>les' ,law1 #afe ,*ladni's figures1 #cha ,*oke coils1 #dgj ,coeffici5t ( expansion1 def9itions1 #agj gases1 #afg liquids1 #afh solids1 #afi ,coh]]1 #ddi ,cohesion1 #ba1 #cc ,color1 #dce bodies1 #dce complem5t>y1 #dcf prim>y1 #ddj prismatic1 #dcc !ory ( color vision1 #ddj ?ree-color pr9t+1 #ddj ,commutator1 #cce1 #ccf ,compass1 #bcj1 #bdj ,concave l5s1 #dah ,cond5s]1 #bfj1 #dgd ,conductors1 #bdf ,cons]vation ( en]gy1 #abg ,cont95tal code1 #dei comp>$ ) ! ,morse1 #deb ,convection1 #agi curr5ts 9 nature1 #aha draft ( a *imney1 #ahj ,convex l5s1 #daf ,cool+1 artificial1 #baj ,corpuscul> !ory1 #ddb ,c\lomb1 #bij met]1 #bia ,c\ple1 #aja ,critical angle1 #dad ,crookes' tube1 #def ,cry/allization1 #bh melt+ po9t ( "s cry/all9e sub/ances1 #bjc ,daniel cell1 #bgf ,decl9ation1 #bdj ,d5sity1 #ch1 #eb me?ods = f9d+1 #ec ,dew1 #aib ,dew po9t1 #aic ,diffusion ( gases1 #ac ,dipp+ ne$le1 #bdj ,direct ,curr5t1 #ccg ,disp]sion1 #dcc ,di/illation1 #bjh ,draft ( a *imney1 #ahj ,dry cell1 #bge ,dynamo1 #ccj1 #ccc ,dyne1 #ic ,eye1 !1 #dbc action (1 9 vision1 #dbc defects (1 #dbe ,e>1 !1 #chf trumpet1 #cfa ,e>?'s magnetism1 #bch ,e*oes1 #cfb ,eclipses1 #cia ,effici5cy1 #adb eng9es 7te/s71 #bai ma*9es1 #adb ,ela/icity1 #ca ,electric bell1 #bfi1 #bhg *>ge1 di/ribution (1 ^u a conductor1 #bec circuit1 #bfi curr5ts1 #bfg s+le phase1 #dgi ?ree phase1 #dgi effects1 #bgg induc$1 #cbf dis*>ge 9 r>efi$ air1 #deb motor1 #cci scre51 #bef ,electrical capacity1 #bei fields1 #bdg ,electrification1 #bdc ,electrolysis1 #cjh laws1 #caa practical uses1 #caa ,electromagnet1 #bha ,electromagnetic !ory ( light1 #def ,electromotive =ce1 #bfg unit (1 #bie ,electron !ory1 #beb ,electrophorus1 #bfc ,electroplat+1 #cjg ,electroscope1 #bdd ,electro/atic induction1 #bdh ,en]gy1 #abj cons]vation1 #abg fall+ wat]1 #aeb =ms1 #abe human body1 #abf ,en]gy1 k9etic1 #aba pot5tial1 #abj transf]5ce & trans=mation1 #abd ,eng9es1 #bac ,eng9es1 gas1 #bbb /eam1 #bac turb9e1 #bbe ,equilibrant1 #ha ,equilibrium1 #ajf neutral1 #ajg /able1 #ajf /ability1 #ajh un/able1 #ajg ,erg1 #aai ,e!r1 #agg ,evaporation1 #ah cool+ effect1 #ai1 #aig rate1 #aih ,expansion1 coeffici5t1 #afh gases1 #afg liquids1 #afh peculi>ity1 9 wat]1 #afh solids1 #afi wat]1 on turn+ to /eam1 #bjf ,fall+ bodies1 #aji exp]im5tal /udy1 #aaa laws1 #aac ,float+ bodies1 #dh ,fluoroscope1 #dee ,foot c&le1 #cif ,=ce1 #gi dyne1 #ic effectiv5ess1 #acd graphic repres5tation1 #hj liquid1 aga9/ any surface1 #ch measur+1 #gi mom5t1 #ii p>allel1 #ajj resolution1 #if units1 #hc ,=ces1 p>allel1 #ajj ,frankl9's !ory ( electricity1 #beb ,fraunh(] l9es1 #dci ,freez+1 evaporation1 #aig1 #aii mixtures1 #baj ,friction1 #adg1 coeffici5t1 #adi fluid1 #aej k9ds1 #adg ,friction1 laws1 #aej r$uc+1 #adh uses1 #adi ,galvanomet]s1 #bhi ,galvanoscope1 #bfi ,gas eng9e1 #bbb effici5cy (1 #bbd ,gas met]1 #ge ,geissl] tubes1 #dec ,gravitation1 #ajc law1 #ajd ,gravity1 #hh1 #ajd accel]ation due to1 #aaa cell1 #bgg c5t] (1 #aje ,hail1 #aic ,he>+1 #chf ,heat1 capacity = wat]1 #bja conduction1 #agc con/ants = transmission1 #bbj convection1 #agi effects1 #afa eng9es1 #bac1 #bbb equival5t ( fuels1 #bai fusion1 #bja measurem5t1 #bjj me?ods ( transmitt+1 #agc produc$ by electric curr5t1 #cah radiation1 #agf s\rces1 #aei units1 #afb vaporization1 #bje "w1 #bab ,heat+ ( build+s1 #ahb direct & indirect radiation1 #ahf hot air1 #ahc wat]1 #ahf pl5um sy/em1 #ahg /eam1 #ahf vacuum /eam1 #ahg vapor /eam1 #ahg ,h]tzian waves1 #bfb1 #ddi ,hooke's law1 #cc ,horse p[]1 #abc electric equival5t (1 #abc ,humidity1 #aid ,hydraulic press1 #db elevator1 #dd ram1 #gb ,hygromet]s1 #aid ,hygrometry1 #aia conditions = saturation1 #aib dew po9t1 #aic fog1 #aic =mation1 ( dew1 #aib humidity1 #aid hygromet]s1 #aid importance1 #aia ,hypo!sis1 #c ,images1 concave mirrors1 #dje con/ruction1 #dje def9ition1 #cib pla9 mirror1 #dja small ap]tures1 #cia ,imp$ance1 #dgb ,inc&esc5t lamp1 #cbj ,incl9$ plane1 #adc ,inductance1 #dga ,induction coil1 #cdc ,in]tia1 #hg ,insulators1 #bdf ,int5sity ( s\nd1 #cfc ,int]f]5ce1 light1 #ddb s\nd1 #cgd ,j\le1 #abj1 #cai ,laws1 boil+1 #bjh ,boyle's #fc ,*>les'1 #afe electric action1 #bdc fall+ bodies1 #aac float+ bodies1 #dh gravitation1 #ajd ,hooke's1 #cc induc$ curr5ts1 #cbf int5sity ( light1 #cid ,l5z's1 #cbh liquid pressure1 #cg ma*9es1 #aca magnetic action1 #bbi motion1 #hg ,ohm's1 #bih p5dulum1 #aaf reflection1 #cii refraction ( light1 #daa vibration ( /r+s1 #cgh ,l5ses1 a*romatic1 #dcd effect on light1 #dag equation1 #dba =mation ( images1 #dah =ms1 #daf ,leclan* cell1 #bge ,lev]1 #acb ,leyd5 j>1 #bfa oscillatory nature ( ! dis*>ge1 #ddh ,light1 comp>$ ) s\nd1 #chh1 #ddd electromagnetic !ory1 #def int5sity1 #cid int]f]5ce1 #ddb pol>ization1 #dde rectil9e> propagation1 #chi reflection1 #cif total reflection1 #dac ,lightn+1 #bed ,l9es1 ( =ce1 #bcc agonic1 #bdj isogonic1 #bdj ,liquids1 pressure1 #cf ,local action1 #bgc ,lum9\s & illum9at$ bodies1 #chh ,ma*9es1 #abi advantages1 #abi _c create en]gy1 #acj effici5cy1 #adb law1 #aca me*anical advantage1 #acd ! six simple1 #acb uses1 #abi ,magnetic action1 #bbi fields1 #bcc1 #dff induction1 #bca1 #bcf p]meability1 #bcg poles1 #bbi prop]ties1 #bcj ret5tivity1 #bca sub/ances1 #bcj effect ( electric curr5t1 #bgi ,magnetism1 #bbh ,magnetism1 !ory1 #bcb ,major & m9or triads1 #cfi ,magneto1 #cbh ,magnetoscope1 #bcj ,magnets1 #bbh poles1 #bbi ,major scale1 #cff ,manometric flames1 #chb ,matt]1 #d effect ( heat1 #e molecul> !ory1 #e prop]ties1 #cd /ates (1 #d /ates (1 def9$1 #e ,me*anical advantage1 #acd ,megaphone1 #cfe ,melt+ po9ts1 #bjc ,m]cury arc rectifi]1 #cdg ,metric sy/em1 #h ,microscope1 #dbg ,mirage1 #dad ,mirrors1 #djj concave1 #dje convex1 #djg p>abolic1 #dji plane1 #dja ,molecul> motion 9 liquids1 #ah 9 gases1 #ac 9 liquids & solids1 #bg 9 solids1 #ca ,molecules1 motion1 #af size1 #ac ,mom5t ( =ce1 #ii1 #acc ,mom5tum1 #hg law (1 #ib ,motion1 #he accel]at$1 #hf curvil9e>1 #hh direction1 #hf fir/ law1 #hg modes1 #he second law1 #ib ?ird law1 #ic uni=mity1 #hf ,motor 7electric71 #cci ,a4 ,c4 s]ies1 #dhb induction1 #dhc syn*ron\s1 #dhe ,muffl]1 #bbd ,musical in/rum5ts1 #cgg int]val1 #cfh nom5clatures1 table1 #cfi ,musical s\nds1 *>act]i/ics #cfd ,newton's ,laws ( motion1 #hg ,nodes1 9 pipes1 #chd 9 /r+s1 #cgi ,noise & music1 #cfc ,ohm1 #bid ,ohm's ,law1 #bih ,op]a glass1 #dbh ,optical illusions1 #cij1 #djd in/rum5ts1 #dbc cam]a1 #dbf eye1 #dbc microscope1 #dbg op]a glass1 #dbh prism field glass1 #dbi project+ lant]n1 #dbg telescope1 #dbh ,organ pipes1 clos$1 #chd nodes1 #chd op51 #chd ,oscillatory dis*>ge1 #ddh ,osmosis1 #ai ,outl9e ,review1 curr5t electricity1 #cbe =ce & motion1 #aah heat1 #bbg induc$ curr5ts1 #cec light1 #ddf magnetism & /atic electricity1 #bff s\nd1 #chg "w & en]gy1 #aeh ,ov]tones1 #cgi ,pascal's pr9ciple1 #da ,p5dulum1 comp\nd1 #aae laws1 #aaf simple1 #aae uses1 #aaf ,pepp]'s gho/1 #djd ,p]meability1 #bcg ,phonograph1 #chc ,physics1 def9ition1 #d ,photomet]1 #cid ,photometry1 #cic ,pit*1 #cfe ,pol>ization1 ( light1 #dde ( voltaic cells1 #bgc ,portraits1 ,bell1 #dca ,edison1 #bhe ,f>aday1 #cca ,galileo1 #hi ,gilb]t1 #bag ,helmholtz1 #cig ,huyg5s1 #cig ,j\le1 #bag ,kelv91 #cca ,m>coni1 #dca ,morse1 #bhe ,newton1 #hi ,pot5tial1 #beg ,p[]1 #abc electric1 #caf p[] factor1 #dgf transmission ( electric1 #dgf wat]1 #aeb ,pressure1 air1 #ef atmosph]ic1 #eh ,pressure1 def9ition1 #cg effect on liquids & gases1 #fb law ( liquid1 #cg ,prism field glass1 #dbi ,project+ lant]n1 #dbg ,pro(-plane1 #bdd ,pulley1 #aci ,pumps1 air1 #ff cond5s+1 #fg wat] 7lift1 #fh1 =ce1 #fi7 ,quality ( musical tones1 #chj ,radiation1 #agf sun's1 #agh ,radio-activity1 #deg ,radiomet]1 #agg ,radium1 #deg ,ra9b[1 #dcf ,reactance1 #dgb ,reflection1 light1 #cif multiple1 #djd s\nd1 #cfj total ( light1 #dac ,refraction1 #daj cause1 #dab index1 #dab light1 #daj 9 plates1 prisms1 & l5ses1 #dac ,resolution ( =ces1 #if ,resi/ance1 cells 9 s]ies1 & p>allel1 #cjb conductors1 #bic 9 s]ies & p>allel1 #bii1 #cjj unit1 #bid volt-ammet] me?od = f9d+1 #cjd ,resonance1 #cga ,resonator1 #cgc ,resultant1 #ha ,ret5tivity1 #bca ,"r h& rule1 #bgi ,rot>y conv]t]1 #dhf ,sci5ce1 def9ition1 #b ,screw1 #add ,%ad[s1 #cij ,s+le phase curr5ts1 #dgi ,siphon1 #gj 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