106 ON DIELECTRICS. 



If the body interposed were a conductor, the loss of potential 

 of the conductor A would be V - V. The effect of introducing the 

 dielectric has been to lower the potential on the conductor A, and 



the fall is a fraction equal to i of what would be produced by a 



f* 

 conductor of the same dimensions as the dielectric. This simple 



result is, however, peculiar to the conditions chosen ; it would not 

 be the same if the dielectric were not bounded by the level surfaces 

 of the original system. 



123. When the dielectric occupies the whole space between the 

 conductors A and B, so as to form a closed condenser, we have 

 V = V lt V' = V 2 , and 



For the same charge the difference of potentials has become //, 

 times less, by substituting for the layer of air a dielectric whose 

 specific inductive capacity is equal to /A. In other words, the 

 capacity of the system has become /* times as great. This is just 

 Faraday's experiment. 



The above remark (119) gives directly the latter results. By 

 interposing a dielectric of the specific inductive capacity //., in the 

 space which separates A and B, the form of the equipotential 

 surface is not modified, but the apparent density at each point 

 becomes /* times less than the real density ; the effect is the same 

 as if the system, retaining its original capacity, had received a 

 charge //. times smaller. 



124. We may represent to ourselves the preceding phenomenon 

 in still another manner. 



Let us suppose that the dielectric comprised between the con- 

 ductors A and B (Fig. 26) is divided into an odd number of infinitely 



thin laminae a, /?, a', /?' by equipotential surfaces of the original 



system, so that the variation in potential is the same in all the layers 

 a, a' ... respectively, as in the layers /?, /3' . .. and that we have, 

 therefore, 



/ S\ 1 Q.1 



y _ v" _ v" _ yiv _ _ jj 



Let us finally place on each of these surfaces masses equal in abso- 

 lute value to those on the surfaces S x and S 2 of the conductors 



