336 



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



Table Y. A. 



Observations on the Periodic Variation of the Intensity of the 

 Light of an Alternating Current Arc. 



Light from centre of Arc. Long Arc. 



Frequency = 50 ~ . 



Length of arc = 1*2 cm. 



Potential- difference (P.D.) of carbons ) _ r o i, 



(mean square value) J 



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

 Power expended in arc ..... = 742 watts. 

 Pressure at alternator terminals ... = 88 volts. 



Angle 



of 

 Phase. 



Current 

 through Arc 

 (instan- 

 taneous 

 value.) 



P.D. 



of Carbons 

 (instan- 

 taneous 

 value.) 



Angle 



of 

 Phase. 



Intensity of 



Light from 



Centre 



of Arc. 









+ 20-4 



+58-6 



10 



40 





20 



+159 



4-48-6 



31 



44 





40 



+ 8-4 



4-26-4 



52 



9 





60 



+ 07 



- 7-6 



76 



12 



Arc out. 



80 



- 3-6 



-46 



98 



19 



)> » 



100 



- 8-1 



-53-6 



120 



24 





120 



-15-1 



-63-6 



142 



72 





140 



-18-6 



-67'6 



164 



50 





160 



-196 



-68 



187 



63 





180 



-176 



-67 



; 209 



44 





200 



-12-6 



-53-6 



232 



12 



Arc out. 



220 



- 5-6 



-21 



253 



7 



n >> 



240 



- 06 



+24 



275 



7 



»> »» 



260 



+ 4-4 



+47 



297 



34 





280 



+ 8-4 



+53 



320 



62 





300 



+ 17-4 



+55 



343 



87 





320 



+2L4 



+596 



348 



63 





340 



+ 23-4 



+ 59 6 



326 



78 





360 



+20-4 



+55-6 









340 



+ 22-4 



+59-6 









320 



+21-4 



+ 58-6 









