,,the ,,fifteen ,,watt ,,tungsten ,,lamp ,,by ,,clair ,,elmore ,,anderson ,b4 ,s41 ,university of ,illinois1 #aiaa ,,thesis ,submitted in ,partial ,fulfillment of the ,requirements for the ,degree of ,,master ,,of ,,science ,,in ,,electrical ,,engineering ,,in ,,the ,,graduate ,,school ,,of ,,the ,,university ,,of ,,illinois #aiab ,illustration3 ,,university ,,of ,,illinois ,,the ,,graduate ,,school ,may #ca1 #aiab ,i ,,hereby ,,recommend ,,that ,,the ,,thesis ,,prepared ,,under ,,my ,,supervision ,,by ,,clair ,,elmore ,,anderson ,,entitled ,,the ,,fifteen ,,watt ,,tungsten ,,lamp ,,be ,,accepted ,,as ,,fulfilling ,,this ,,part ,,of ,,the ,,requirements ,,for ,,the ,,degree ,,of ,,master ,,of ,,science ,,in ,,electrical ,,engineering ,ernst ,berg ,in ,charge of ,major ,work ,ernst ,berg ,head of ,department ,recommendation concurred in3 ,morgan ,brooks ,ellery ,b ,paine ,j ,m ,bryant ,committee on ,final ,examination ,,contents ,page ,i4 ,introduction1 #a ,,ii4 ,description of ,lamps and ,tests1 #b-d ,,iii4 ,characteristic ,curves1 #e-ab ,,iv4 ,spherical ,candle ,power1 #ac-ae ,v4 ,phenomena of 8,overshooting01 #af-ah ,,vi4 ,theories of 8,overshooting01 #ai-bj ,,vii4 ,amount of 8,overshooting01 #ba-bb ,,viii4 ,curves of 8,overshooting01 #bc-bf ,,ix4 ,conclusions1 #bg ---------------------------------------- -------------------------------- ,,the #ae ,,watt ,,tungsten ,,lamp ,i4 ,,introduction4 ,since the introduction of the tungsten lamp some five years ago1 the manufacturers have attempted continually to produce smaller and smaller units in the standard voltages4 ,the latest lamp offered today is the #aae volt1 #ae watt1 tungsten1 and it is the purpose of this paper to show the characteristics of this lamp1 how it compares with the larger units as to life under different conditions and its behavior in general4 ,first of all1 it must be borne in mind that these tests have been made upon a comparatively small number of lamps1 and for that reason the results should not be taken as absolutely conclusive4 ,for the life tests1 at least #ajj lamps should have been used under each condition1 but this was impossible because of the expense4 ,special attention has been given to the phenomenon of 8overshooting04 ,an entire year could have easily been spent investigating this subject1 and the writer regrets that lack of time has prevented more elaborate and comprehensive tests of this strange phenomenon4 ,,ii4 ,,description ,,of ,,lamps ,,and ,,tests4 ,the total number of #ae watt lamps tested was #bd1 one half of which was obtained directly from the manufacturer and the other half bought in open market4 ,it is well to mention at this time that this may have been the cause of the different qualities as brought out by the life tests4 ,the lamps were rated at #a4ca watts per horizontal candle power and were supposed to have a useful life of #ajjj hours4 ,the voltage ratings of those obtained from the factory were #aad - #aab - #aaj and those bought in open market were #aae - #aac - #aaa4 ,the correct efficiency of the lamps as found by test was #a4cd watts per candle power4 ,a shot diagram follows which shows the actual rating of the lamps at high efficiency4 ,all readings were made by a ,lummer-,brodhun photometer and the voltmeters and ammeters used were carefully standardized4 ,the ammeter was placed beyond the voltmeter in order to get the true current taken by the lamp4 ,the drop across the ammeter was taken into account in the voltmeter readings4 ,life tests were made under two conditions1 namely1 a shock test where the lamps received severe vibrations and a test under ideal conditions1 i4e4 no jar and constant voltage4 ,in order to obtain vibrations for the lamps upon the shock test1 a small motor1 with its shaft pulley off set1 was screwed rigidly to a table4 ,the lamps were placed in a normal position upon the table by means of wooden frames4 ,the result was that when the motor was running it had a pounding effect1 thus putting the table1 consequently the lamps1 in a state of severe vibration4 ,the filaments of the lamps could be seen violently shaking for some distance4 ,the test was indeed a hard one1 and one that would not be found in many actual cases4 ,it is very doubtful if railway lamps are subjected to such a strain and they are of the heavy filament low voltage type4 ,the following photograph shows the arrangement above described4 ,ten #ae watt lamps were used on this test1 the remainder shown being #bj and #be watt and carbons4 ,illustration3 photograph1 arrangement of tungsten lamps ,illustration3 ,shot diagram for #ae watt lamps ,,iii4 ,,characteristic ,,curves4 ,figure #a1 ,page #h1 shows the variations of the candle power with the voltage1 current and watts4 ,figure ,,ii shows the relation between candle power and the efficiency1 watts per horizontal candle power1 and also the variation of the candle power with the resistance4 ,an empirical formula for the candle power expressed as a function of the watts is cp ,,kwx where ,k is a constant of the lamp and ,w denotes the watts4 ,from the curve when cp #e1 watts #aa4a and when cp #ae1 watts #ag4e dividing cp#a_/;cpa ,,kw#ax_/,,kwax substituting #e_/ae #aa4ax_/#ag4ex and log #c x log #aa4a x log #ag4e 4#dgga #a4jdecx #a4bdcjx 4#aihx 4#dgga x #b4da solving for the constant ,k #e ,k #aa4ab4da #e #ccb ,k ,k 4#jaej and the final equation for the candle power is cp 4#jaej w#b4da ,in the same way1 the candle power may be expressed in terms of the voltage and this is found to be cp #ccd #aj-i ,e#c4fh ,this formula checks precisely with the one used in the engineering department of the ,general ,electric ,company at their lamp works1 ,harrison1 ,n4,j4 ,the horizontal distribution curve of a lamp with its filament mounted as is the modern tungsten is nearly a circle4 ,this is not true1 however1 in the case of vertical distribution and this curve is shown1 ,figure ,,iii4 ,as will be noted1 the tip candle power is only about #bc per cent of the horizontal4 ,life ,tests4 ,the results of the life tests were very surprising4 ,the lamps upon the test under ideal conditions1 namely1 no vibrations and constant voltage1 had only an average life of #dfj hours1 while every one of those upon the shock test are still burning at the present time1 having been burned #cjj hours4 ,in order to make the test still more severe1 the lamps were subjected to vibrations without voltage being impressed1 and as yet1 not a filament has broken1 the total time being #djj hours4 ,it was impossible to give more time to these lamps as was done for those under ideal conditions1 for the reason it was thought unadvisable to leave the motor1 which gave the vibrations1 running over night4 ,the curves have the same general form for the two conditions but the variations are far more great for the lamps which were upon the shock test4 ,the reason for this is that the vibrations were so severe as to shake parts of the filament together thus giving a partial short circuit1 causing great variations in candle power4 ,illustration3 ,fig ,i ,characteristic ,curves for #ae watt tungsten lamps ,lamp of average rating used ,illustration3 ,fig ,,ii ,characteristic ,curves for #ae watt tungsten lamps ,lamp of average rating used ,illustration3 ,fig ,,iii ,vertical ,distribution for #ae watt #aae volt ,tungsten lamp ,illustration3 ,life ,tests #ae ,watt #aae ,volts ,tungstens ,conditions ,ideal o--,burned ,out ,illustration3 ,life ,tests #ae watt #aad volts tungsten ,shock ,conditions ,all lamps still ,burning ,,iv4 ,,spherical ,,candle ,,power4 ,owing to the absence of an integrating photometer1 the mean spherical candle power has been found by ,kennelley's graphical method4 ,this method is very simple as compared with ,rousseau's and has the advantage of yielding the mean spherical intensity as a one dimensional quantity4 ,this dispenses with the use of a planimeter or equivalent measuring surface device4 ,it consists essentially in determining graphically from the given polar curve an evolute and the involute of the same and then projecting this involute upon a vertical line4 ,half the length of the projection is equal to the mean spherical intensity to the same scale as the original polar curve4 ,figure ,,iv shows the method and is explained thus3 ,the polar curve ,o ,a ,h ,b corresponds to the distribution of intensity from an inverted incandescent lamp having its base at ,v and tip at ,v4 ,this is not precisely true but the only variation to speak of is that the tip candle power does not fall off so much as the curve between ,b and ,o4 ,this variation is slight1 however4 ,the mean horizontal intensity is ,,oh1 the diameter of the circle1 and in this case is equal to #ab4d candle power4 ,in the diagram the construction is adapted to zones of #cj and the radii of the midzones found i4e4 at #ge1 #de1 #ae1 -#ae1 -#de -#ge4 ,these are marked by dotted lines ,o t1 ,o s1 ,o r1 ,o r1 ,o s1 ,o t respectively4 ,with radius ,o r and center ,o1 the arc hra is described through an angle of #cj4 ,the radius ,oa is drawn at the end of the arc4 ,a distance ,ab is measured from a along a ,o equal to ,o s1 the second midzone radius4 ,with a center b and radius ,o s1 the arc ac is described through an angle of #cj so that bc makes an angle of #fj with the horizontal ,,oh4 ,the line bc is drawn at the end of this arc4 ,from c towards b1 a distance cd is marked off equal to ,ot1 the third midzone radius4 ,with center d and radius ,o t1 the arc ce is described through an angle of #cj so that de makes an angle of #ij with the horizontal ,,oh4 ,the line de is drawn4 ,the arc hace is extended from the horizontal to the vertical beneath in the same manner as above by steps of #cj with centers ,o1 b1 and d1 and radii ,or1 ,,os and ,ot respectively4 ,the curve ecarrace is now continuous and complete4 ,a vertical line ,,qq is drawn through the convenient point ,h and the points e c a a c e are projected upon the same4 ,the length ,,hq1 is the upper hemispherical intensity and the length ,,hq the lower hemispherical intensity4 ,their arithmetical mean is the mean spherical intensity4 ,since in this case the upper and lower hemispheres are symmetrical ,,hq ,,hq ,,qq_/#b mean spherical intensity4 ,by measurement this half length is found to be #c4abe inches and from the scale used this corresponds to #i4fg candle power4 ,the spherical reduction factor for these lamps is1 then #i4fg_/ab4d #gh ,illustration3 ,fig ,,iv ,kennelly's ,diagram for ,spherical ,c4 ,p4 ,v4 ,,phenomena ,,of 8,,overshooting04 ,the singular property of the tungsten lamp to 8overshoot0 or to give temporarily a higher initial than normal candle power1 was first discovered by ,john ,b4 ,taylor and is explained in the following manner3--,the filament of the carbon incandescent lamp possesses a negative temperature coefficient2 that is to say1 a rise in voltage causes a more than corresponding rise in current and when the lamp is connected to a source of constant potential1 the current starts at a comparatively small value and increases to a maximum when the lamp has attained full candle power4 ,in the case of the tungsten lamp1 the situation is just the reverse1 since tungsten has a positive temperature coefficient4 ,when the lamp is connected to a constant potential supply the current is a maximum when the lamp is cold and decreases to a final value when the lamp reaches full brilliancy4 ,the most important difference between the two lamps due to these different characteristics is that while a tungsten lamp reaches full candle power the instant the current is turned on a carbon incandescent lamp comes up to full candle power only after a perceptible period of time4 ,the apparent temporary increase in the candle power of a tungsten lamp was observed early after the lamp was invented but it was generally ascribed to some possible physiological action due to the slow contraction of the pupil of the eye4 ,the following curve was obtained by means of the oscillograph and shows clearly the rush of current for the first instant after the lamp is turned on4 ,the break in the curve is due to an imperfection in one of the operating switches and has nothing to do with any characteristic of the lamp4 ,the cycle wave was put on merely to obtain the time4 ,illustration3 photograph1 current after lamp is turned on ,in order to prove that this overshooting occurs1 an actual photograph of the intensity has been made4 ,this was obtained by making a box #a #a #c absolutely light proof and arranging a lamp inside so that it could be turned on and off at will4 ,a slit1 fitted with a shutter1 was cut in one end of the box which permitted the light to fall upon a revolving oscillograph film4 ,the film holder was attached to the box with thin metal strips and revolved by means of a small motor4 ,as is seen the whole arrangement was nothing more than a large camera4 ,the following photograph shows the phenomenon quite clearly1 point ,a denoting where the lamp was turned on4 ,illustration3 photograph1 intensity of light1 overshooting ,,vi4 ,,theories ,,of 8,,overshooting40 ,the theory given by ,taylor to account for the 8overshooting0 of tungsten lamps is based on the fact that there is a small amount of residual gas in the lamp1 which is attracted to the walls of the lamp when it is cold2 and when the lamp is lighted and warms up1 this residual gas is driven off lowering the vacuum4 ,with a high vacuum1 practically all the energy must be radiated from the filament2 conversely1 on a lowering of the vacuum1 some of the heat is carried away by convection and conduction4 ,when all the heat is carried away by radiation the filament runs at a higher temperature and will give more light4 ,another theory is that a cold tungsten filament lamp absorbs and occludes certain gaseous substances from the low pressure space within the chamber4 ,owing to the presence of these gases the filament shines more brightly when first brought quickly to incandescence1 but after the gases have been driven off by the heat1 the extra luminescence disappears and can be regained only by prolonged cooling and rest4 ,still another theory1 and the one that seems the most logical to the writer1 is that the increase of resistance accompanying the rise of temperature takes a certain small interval of time so that when the temperature is rising at the rate of thousands of degrees per second1 the resistance lags perceptibly4 ,the resistance does not suppress the current as quickly as it should and an extra rush of current and heat energy goes through the filament1 raising the temperature above normal1 with a corresponding increase in brilliancy4 ,,vii4 ,,amount ,,of 8,,overshooting04 ,in order to determine the amount of over shooting1 the writer has made photographs as shown below4 ,number one was made with the lamp under voltage1 number two by using normal voltage and suddenly turning the lamp on by means of a snap switch1 thereby obtaining the overshooting1 and finally number three was made by impressing voltage above normal4 ,the pictures were obtained by using the photographic arrangement as before described4 ,all three prints were made from the same film1 that is the three pictures were made upon one film thus insuring the same development and printing for all4 ,the print has been cut merely to allow a closer comparison of the intensities4 ,illustration3 amount of over shooting ,it is seen that number three compares favorably with the overshooting as shown by number two and the candle power corresponding was found to be approximately #ej greater than normal4 ,it is not claimed that every lamp will overshoot this amount as the degree of vacuum or other factors of individual lamps may play an important part in this phenomenon4 ,there is no doubt1 however1 that this strange fact really occurs and is not due to physiological reasons4 ,,viii4 ,,curves ,,of 8,,overshooting04 ,in order to prove that the law of resistances1 namely1 ,r ,ro7#a t7 does not hold for the first instance after closing the switch on a tungsten lamp1 the following curves have been plotted4 ,number ,v4 has been taken from the oscillograph record shown in the first part of this paper and shows that about 4#jbd second elapses before the current becomes normal4 ,knowing the current at any instant as given by this curve1 it is easy to find the resistance at the same instant by ,ohm's law1 the electromotive force being a constant and known value4 ,curve ,,vi shows this relation4 ,curves ,,vii and ,,viii are approximate values and not absolute4 ,now from the temperature curve1 values are taken and substituted in the formula for resistance1 ,r ,ro7#a t71 the resulting curve being ,figure ,,ix4 ,it is seen that curves ,,vi and ,,ix do not take the same values at all until after a brief interval of time has elapsed4 ,curve ,,vi is absolutely correct1 however1 as these values have been obtained from the oscillograph record4 ,consequently1 the assumption upon which curve ,,ix is based must be incorrect for the first 4#jbdth of a second and the conclusion is that the law of resistances does not hold4 ,this result tends to strengthen the theory of the lag of resistivity for the 8overshooting0 of a tungsten lamp4 ,illustration3 ,fig ,v ,illustration3 ,fig ,,vi ,illustration3 ,fig ,,vii ,illustration3 ,fig ,,viii ,illustration3 ,fig ,,ix ,r ,ro#a t ,,ix4 ,,conclusions4 ,the following conclusions may be drawn from the results of the tests4 #ast1 ,that the quality of the two sets of lamps was greatly different4 #b;d1 ,that it is doubtful if the #ae watt1 #aae volt1 tungsten lamp as first put upon the market met the guarantee as to life4 ,this conclusion is reached by tests in the laboratory and experience with lamps installed in residences4 #c;d1 ,that the tungsten lamp is subject to overshooting4 #dth1 ,that during this period the initial candle power may be as much as #ej above the normal4 #eth1 ,that the most probable theory of overshooting is the lag of resistance behind the temperature4 ---------------------------------------- -------------------------------- ,,transcriber',s ,,note ,italicized phrases are presented by surrounding the text with underscores4 ,superscripted characters are represented by preceding with a caret 77 symbol4 ,when longer than one digit1 they are also surrounded in curled brackets4 ,subscripted characters are represented by preceding with an underscore and enclosing in curled brackets4 ,fractions are represented horizontally using the slash _/ symbol4 ,the original separated the numerator and denominator horizontally1 separated by a line4 ,punctuation has been normalized4 ,except in the following cases1 variations in hyphenation1 spelling and spacing have been retained as they were in the original publication4 ,chapter #b3 ,lumer-,brodhum photometer -- ,lummer-,brodhun photometer ,chapter #d3 ,what appear to be hand-drawn primes in the text have been confirmed as3 ,the arc hace -- ,the arc hace4 e c a a c e -- e c a a c e ,figure ,,iv ,there are two points b radiating from point ,o4 ,the lower is likely to represent b4 ,chapter #e3 inportant difference between -- important difference between