the Induction- Coil. 711 



Plate XTI. fig. 8, is evidently sufficiently close to justify the 

 application of the method to the present case. The damping 

 of the waves is much greater in the photograph than in the 

 calculated curve. This is also the case in the other experi- 

 ments described below, and is to be expected since the only 

 cause of damping taken into account in the calculation is 

 that which arises from the resistances of the circuits. 



The calculated maximum value of: the secondary potential 

 is 19650 volts, and the amplitude of the first wave in the 

 photograph is 0'9276 cm. Now the standardising curve 

 obtained with the air-core coil showed that a deflexion of 

 0*3032 cm. in the photograph coiTesponds to 10200 volts. 

 Hence taking the deflexion as proportional to the square of 

 the potential, the amplitude of the first wave represents a 

 maximum potential of 17850 volts. 



When it is remembered that the damping due to hysteresis 

 and condenser losses have been entirely neglected, the 

 agreement between the calculated and observed values of 

 the maximum secondary potential is perhaps as close as 

 could be expected. 



Case 11. — This case is similar to the first except that the 

 primary coil with its iron core was placed further inside the 

 secondary in order to increase the secondary self-inductance 

 and the coupling coefficient. The secondary capacity (a 

 variable condenser with paraffin-oil dielectric) was adjusted 

 so as to give a form of oscillograph curve slightly different 

 from that of Case I. The constants of the circuits were : — 



1^ = '02331 henries. 



L 2 = 428'l 



M = 2'436 



V =0-5949 



L\ = 1 5' 9 5 microfarads. 



C 2 = 0-000499 „ 



R l9 E 2 as before. 



The frequencies, calculated by (2) , were 



n 1 = 219-8, ?z 2 = 642'3, 



and, with 2 = 4 - 02 amperes, the expression for the secondary 

 potential in volts is 



2V 2 = 15320 e~ b ' m sin (79146;-0'51) 



-5247 e -' ol '*' ot sin (231221^-1-49). 



