209-213] Images 185 



212. The method of images also supplies a solution when the conductor 



7T 



consists of two planes intersecting at any angle of the form - , where n is 



any positive integer. If we take polar coordinates, so that the two planes 

 are 6 = 0, = , and suppose the charge to be a charge e at the point r, 6, 

 we shall find that charges 



(r, 0), (r, 6 + %), (r, + %), .... 



e at 



e at 

 give zero potential over the planes 



7T 



Charge induced on a sphere. 



213. The most obvious case, other than the infinite plane, of a surface 

 whose equation can be expressed in the form (125), is a sphere. 



FIG. 61. 



