ELECTRIC DISTRIBUTION AND CONDENSATION. 



71 



j 

 V 



j 



section through the poles, as shown at j5, will have the 



same form as a cylinder with hemispherical ends. And 



since it has been shown that a charge of electricity on 



such a cylinder is condensed 



on the ends, it is evident that 



a charge on such a spheroid 



will, in like manner, be con- 



densed on its outer edge. 

 ELECTRIFIED Disc. If a 



flat metal disc, with a thin 



edge, be electrified, the charge 



will go to the outer edge, as in 



the last case. But resistance, 



being in proportion to surface, 



is very small on such an edge, Fig ' 16 - Electrified Spheroid. 



and the charge is rapidly dissipated. Hence such a 



disc, when constructed for the purpose of condensing 



electricity on it, should be pro- 

 vided with a round rim, which 

 may be called a resistance rim. 



If it be insulated, and there 

 be placed on its opposite sides, 

 near the edge, two little metal 

 stands with pointed stems, on 

 which are balanced light metal 

 pointers, having arms of tin- 



Fig. 17-ElectrifledDisc. equal ^^ &g shown j n Fig> 



17, a charge of electricity given to it will cause the 

 pointers to arrange themselves in the direction of the 

 radii, showing that the electric force is from the center 

 outward. 



