328 Prof. J. A. Fleming and Mr. J. E. Petavel : 



Table I. A. 



Observations on the Periodic Variation of the Intensity of the 

 Light of an Alternating Current Arc. 



Light from centre of Arc. Short Arc. 



Frequency = 83*3 ~ 



Length of arc = 0*55 cm. 



Potential-difference (P.D.) of carbons ") _ qq i, 



(mean square value) J ~ 



Current (mean square value) .....-= 14 amperes. 



Power expended in arc =546 watts. 



Pressure at alternator terminals . . . = 104*5 volts. 



Angle of 

 Phase. 



Current 



through Arc 



(instantaneous 



value). 



P.D. 



of Carbons 



(instantaneous 



value). 



Angle of 

 Phase. 



Intensity of 



Light from 



Arc. 











26 



38 



20 







38 



23 



40 



4- 5-6 



4-20-2 



58 



16 



60 



4- 0-7 



4- 02 



76 



6 



80 



- 37 



-24-2 



80 



16 



100 



- 9-7 



-34-5 



102 



24 



120 



-16-2 



-38-0 



132 



47 



140 



-20-3 



-43-0 



146 



60 



160 



-210 



-44-8 



156 



56 



180 



-18-4 



-435 



168 



68 



200 



-130 



-32-5 



176 



57 



220 



- 6-2 



-19-2 



196 



48 



240 



- 04 



4- 1-9 



202 



31 



260 



4- 4-2 



4-25-5 



242 



11 



280 



+ 10-2 



4-38-1 



252 



19 



300 



4-163 



4-40-8 



274 



12 



320 



4-20-0 



4-46-5 



304 



50 



340 



+20-4 



4-48 3 



320 



58 



360 



4-18-4 



4-50-5 



326 

 340 

 346 

 356 



55 

 65 

 63 

 68 



