234 Dr. 0. Lodge on the Electrostatic Force between 



measured j and either adjust Sx until the electrostatic and 

 electrodynamic forces balance, or estimate the outstanding 

 force by a torsion arrangement. Supposing a balance could 

 be got, the impedance of the intervening conductor, for the 

 particular frequency applied, is 



1 



P = 



S/V 



60 



ohms. 



PP 



Leyden-Jar Discharge. 



Next proceed to consider the transient current of a Ley den- 

 jar discharge round the same circuit. 



Let a jar of capacity S charged to potential Y be dis- 

 charged round a circuit whose total resistance and inductance 

 are R a]Q d L respectively. Then the current at any instant 

 after the discharge has begun is 



Vo. - , R« , - . " 1 



i?L 



mt 



sin pt; where 



2L 



and irv L -{-p i 



SL, 



The electrodynamic repulsion between the two wires pre- 

 viously considered, when the discharge occurs, is therefore, 

 applying (2), an impulse : — 



'-"(MS!*"-***-* 



2fil 



En 



(±) 



To investigate the electrostatic attraction completely we 

 should have to take into account the sinuous distribution of 

 potential in space over the circuit ; but, unless the waves are 

 much shorter than usual, the ultimate effect on a short length 

 will be very little different from the effect of a uniform poten- 

 tial alternating sinuously in time, the difference of potential 

 at any instant between the fixed and movable wire being 



V=PC, 



where P is the impedance of the intervening portion of the 

 circuit. 



Hence the electrostatic impulse is, by (1), 



* 



-eH"; 



C*dt 



J27 |SV 2 

 Ka' R 



. S X 2 P 2 . 



(5) 



