710 Prof. E. Taylor Jones and Mr. D. E. Roberts on 



both measuring and calculating the maximum amplitude in 

 this curve the electrometer may therefore be standardised. 



The iron-cored induction-coil was again connected to the 

 oscillograph and photographs obtained for the purpose of 

 measuring the primary and secondary inductances, the 

 coupling coefficient, and the capacities if these were not 

 already known. The values of these constants in the present 

 case were as follows : — 



Li = '02312 henries. 



L 2 =258'3 



M= 1-811 



k 2 =0-5424 



d = 15*95 microfarads. 



C 3 = 0-0004748 „ 



This value of C 2 includes the capacity of the electrometer 

 and of the secondary coil. The resistances of the primary 

 and secondary coils were 0°32 and 14000 ohms. 



The two frequencies oi oscillation, calculated by (2), were 



^ = 237-4, ?i 2 = 737-0, 



and the expression (1) for the secondary potential, taking 

 the primary current i as 5*05 amperes, becomes in volts 



2Y 2 = 15230 e~ 6t sin (S6453£-0'55) 



-4910 <T CS ' 15 ' sin (266334*-*- 1-72), 



in which t is the time in seconds after the interruption of 

 the primary current, and the angles are given in degrees. 

 This was worked out for a number of values of t, the results 

 squared and plotted in a curve the early portion of which is 

 shown in nV. 1. 



Yis. 1. 



Ffo. 2. 













ft 



'ITS 



40 

























Xw~ 



30 



1 



\ 



i 



\ 



\e 



,000- 



1 







\ 







> 



\-l 













T 





\ 









'10 



/ 













/ 



\ 



\ 



\ 









J_ 



K 



) 



V 



. J 







) 1 2 3 4- 5 6 



T. IN THOUSANDTHS Of 

 A SSCC/VD- 



n 



l = ' 



237- 



4, 



n 2 = 



=73' 



r-o, 











' / 



airs 









A 



18 



000- 













000- 



/ 



/ 







/ \ 





/ 



i 



J 





V, 



: 219-8, 



642-3, 



5-05 amp. 



i =4i-02 amp. 



The agreement between this curve and the photograph 



