through a Coil of Variable Inductance, 157 



Let OX (fig. 1) be the axis of time, OY the axis of current. 

 Just before the discharge there is quantity Q = E C on 

 the plates of the condenser. 



Fig. 1. 

 Y 



M 



->N 



/ 



s / / 



' / I 

 / ' 

 / / 



n; 



■N 



k 

 ■N- ^ 



K=0.5 



L?> 



^a 



m 



77Z K X { 77?X 2 



The quantity at any instant T after the discharge has 



occurred is therefore = —Q + 



idt, 



where i is considered 



positive when it tends to diminish the quantity of electricity 

 on the plates of the condenser, and Q must therefore be 

 considered negative. 





<& 





Plot along OZ a length proportional to =5- , and on OX to 

 the same scale, time in seconds. 



If OK= tt ^ n seconds draw KM parallel to OY. 



K Q 



Along Y take a length OX = -^ in amperes to the 

 proper scale. 



