143145] PLANES. 279 



At the surface r=R 2 , we get in like manner, 



Accordingly the capacity of the condenser formed of I units of 

 length of two conductors is 



If we put R z RI = r, and consider T small, 



K _IR_ 27rE^ _ 8 



"27" 47TT " ~ 47TT ' 



where $ is the surface of one condenser plate. 



145. Parallel Planes. If the conductors are two parallel 

 planes, of great extent, parallel to the plane of XY, at a sufficiently 

 great distance from the edges in the space between the plates, F is 

 independent of x and y, and 



V-AM+B. 



If z is measured from the plate whose potential is "Pi, and T is 

 the distance between the plates, 



T 



The surface density on the plate 1 is 



1 8F 1 V 



<JT = 



4?r dn 4?r \dz J z =o 4-7TT 



