508 CONSTANTS OF COILS. 



in one part of the circuit for instance, on the side of the coil a'\ 

 the intensity of the current in the shunt is /+/'. The general 

 equations 



at at at 



give, for the total duration of the variable state, 



mr + (m + m')sMl Q = 0, 

 m'r' ' 



If the resistance s be adjusted so that the discharge m' in the 

 galvanometer is null, we have 



M 



In order that the discharge be null, we must have M>M'; the 

 galvanometer should be placed on that side of the coil on which 

 the induction is weakest. 



As the coils a and a' are always in opposition, and the galvano- 

 meter is in the induced current, we may, lastly, place a shunt S 

 between the two points of the inducing circuit (Fig. 233) for 

 instance, on the side of the coil A'. If, then, I and I' are the 

 currents in the coils A and A', 



which gives, for the whole duration of the variable state, 

 1 +g)m + MI - M'l^ = 0. 



If the resistance S is chosen, so that the discharge m is null, the 

 equation reduces to 



MI = MT . 



As the currents I and I' correspond to a permanent state, we 

 have 



