EFFECT OF INTERPOSING A DIELECTRIC. 



107 



alternately positive and negative, + M on the odd surfaces, and M 

 on the even surfaces, each of -these layers being in equilibrium under 

 the action of the original conductors A and B. 



It is clear that the system thus obtained is in equilibrium. The 

 force is not modified in all the odd laminae a, a', a" . . , but it is null 

 in all the even ones /?, /?', ft" . . . and the potential has a constant 

 value in each of these laminae. It is as if all the even laminae were 

 replaced by conducting layers. 



s rr 



Fig. 26. 



This operation has lowered the difference of potential between 

 A and B. The difference of potential of the surface S : to S", which 

 was originally Vj - V", has, in fact, become V 1 - V, and we have 



In like manner, the original difference of potenial V-V iy , be- 

 tween S" and S IV is reduced to 



V' -V" 



The ratios 



are the same throughout the whole thickness of the dielectric, and 

 we may write 



a a i 



Calculating, in this way, from layer to layer, we see that from the 

 surface S : to the surface S 2 , the potential varies p times less than in 



