560 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



In Figure 20 the current in the primary circuit is drawn above OX, 

 in the curve OJAZ, and the current in the secondary circuit beneath 

 MN. Each of the circuits has a self-inductance of 2 henries, and the 



Figure 19. The curves Q, R, S represent for different relative values'of the 

 mutual inductance the current induced in the secondary circuit of a certain 

 induction coil without iron, when the primary circuit is suddenly closed. 



resistances are 30 ohms and 40 ohms. The mutual inductance is at 

 first V2, and the currents are given by the equations 



C'l = 4 - 2.4 e-io' — 1.6 e- 



C, = -^^(e-'''-e-'''% (27) 



V2 



until the time OG = 1/20, when all the inductances are suddenly 

 doubled. The currents are then given by the equations 



C"i = 4-1.928c-''-0.840e-30', Co = 0.891^-30'- 1.361 c-='. (28) 



