334 



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



Table IV. 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 . = 50 ~ 



Length of arc = 0'32 cm. 



Potential-difference (P.D.) of carbons \ . . a* u 



(mean square value) .... J 



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



Power expended in arc = 504 watts. 



Pressure at alternator terminals . . =; 85 volts. 



Angle of 

 Phase. 



Current 



through Arc 



(instantaneous 



value). 



P.D. 



of Carbons 



(instantaneous 



value). 



Angle of 

 Phase. 



Intensity 



of Light 



from 



Centre 



of Arc. 









+18-4 



4-4L4 



12 



28 





20 



4-13-8 



+38-4 



34 



15 





40 



+ 5-7 



4-21 



56 



24 



Arc going out. 



60 



4- 0-6 



- 8-6 



78 



13 



Arc out. 



80 



- 6 



-22 



100 



14 



Arc out. 



100 



-131 



-25 



122 



18 





120 



-19 



-43 



144 



28 





140 



-19 



-46-5 



166 



20 





160 



-18-3 



-49 



188 



26 





180 



-14*4 



-46 



210 



17 





200 



-102 



-44*6 



232 



15 



xlrc going out. 



220 



- 5-0 



-20 



253 



6 



Arc out. 



240 



4- 11 



4- 68 



274 



4 



Arc out. 



260 



4- 8-6 



4-226 



296 



16 





280 



4-14-5 



4-29 



317 



26 





300 



4-18-9 



4-37-6 



338 



23 





320 



4-22-1 



4-40-6 



360 



30 



■ 



340 



4-20-3 



4-44 



350 



29 



1 



360 



4-18-1 



4-42-6 



328 



23 





340 



+21-5 



4-45-4 









320 



4-211 



4-404 









