Induction- Coil Potentials. 



573 



was used in order that the coupling o£ the two coils might 

 be made as loose as possible. The oscillations were started 

 by interrupting a current o£ 5 amperes in the primary, and 

 the curves were photographed and measured in the usual 

 way. The product I^Ci was calculated from the frequency, 

 the ratio Ei/I^ from the logarithmic decrement, of the 

 oscillation curve. The results of these measurements are 

 given in Table IV. The corresponding quantities for the 

 secondary circuit, L 2 C 2 and R 2 /L 2 , were determined from 

 the period and logarithmic decrement of the oscillation pro- 

 duced in the secondary when a current of 5 amperes in the 

 primary was interrupted. In this experiment the primary 

 condenser was removed, and the secondary coil was connected 

 only to the electrometer and the ball electrodes, so that the 

 secondary capacity was the same as in the final experiments. 

 The values so determined are given under Table IV. It 

 should be observed that these values of L^Cx and L 2 C 2 are 

 maximum values, i. e. they correspond to a magnetizing 

 current of about 5 amperes in the primary coil. 



The effective resistances of the coils in the circumstances 

 of the present experiments, as determined from the damping 

 of the oscillations, are much greater than their resistances 

 for steady currents. The influence of these resistances on 

 the periods of oscillation is, however, neglected in all calcu- 

 lations in the present paper, i. e. both in the determination of 

 LjGi and L 2 C 2 described above, and in the calculation of the 

 frequencies of the coupled system given in the next section. 

 That no great error is thereby introduced is shown by the 

 close agreement between the observed and calculated periods 

 in the final experiments. 



Table IV. 





C.G.S. 



^/iv 



C.G.S. 



Case I 



1-718 . 10 6 

 2-654. 10 s 

 5-593 . 10 G 



149 

 360 

 390 



Case II 



Caselll. . 









l/L 2 C 2 =S-974.l0 6 c. 

 E 2 /L 2 =215 c.g.s. 



a.s. 



Phil Mag. S. 6. Vol. 27. No. 1G0. April 1914. 2 Q 



