1 20 Electrostatic Capacity of a Conductor. 



K/ 



C = 



, R2 Di 



If the cylinders are coaxal, the external conjugate point 

 is at an infinite distance, or 



and the usual expression for the capacity of co-axal cylinders 

 results. 



If the external cylinder becomes a plane, at a finite 

 distance from the other cylinder, its centre is at an infinite 

 distance, or 



K/ 



and .*. C 



1 ^1 

 2log^; 



If the distance between the centres of the cylinders and 

 their radii are given, Di and D2 may be easily expressed in 

 terms of these quantities. 



Thus, it is seen that this method is easily applicable to 

 all the ordinary problems in capacity; with more complicated 

 cases difficulties arise in effecting the requisite integrations,, 

 as must necessarily be the case whatever method is adopted. 



