440 Piranv's Method of Measuring Self-Inductance. 



Evidently there is a complete balance between the in- 

 ductance L which provides the electromotive impulse and 

 the current from the condenser. This balance has nothing 

 to do with the bridge ; obviously in a case like this where all 



the inductances and capacities are confined to one of the 

 branches of the network, the rest of the network may be left 

 out of account altogether. The only part which the bridge 

 plays in the method is to provide a galvanometer which is free 

 from current in the steady state, in order that it may serve 

 to indicate any transient current during the discharge. The 

 network might, therefore, be very much more complex ; as 

 long as the galvanometer were placed in a currentless branch 

 (conjugate with the battery branch) the result would be the 

 same. On the other hand, if it were possible to switch off 

 the current and put in a galvanometer simultaneously, the 

 bridge arrangement could be entirely dispensed with. 



In order to bring out the real significance of the induction 

 phenomenon, we assumed the transient current in the battery 

 branch x to be zero. The result is, however, independent of 

 this assumption. Without further calculation we may observe 

 that an additional current as in the main line must distribute 

 itself over the network as in the steady state, and cannot 

 therefore affect the galvanometer. For confirmation we may 

 repeat the above calculation, dropping the assumption that 

 ,£;=0. From the mesh GTPR we now have (jc — ?/) P = ?/R, and 



