IO4 ON DIELECTRICS. 



The electrical system gives, in the same way, 



From this we deduce 



The flows of induction are therefore proportional to the flows of 

 heat ; the specific inductive capacity playing the same part in the 

 electrical problem as the coefficient of conductivity in the thermal 

 problem. 



122. CHANGE OF POTENTIAL PRODUCED BY INTERPOSING A 

 DIELECTRIC. If we introduce a conductor into an electrical field 

 due to insulated and electrified conductors, the presence of this new 

 body has the effect of diminishing the initial energy of the system. 

 The introduction of a solid or liquid dielectric produces the same 

 effect to a lesser degree. 



Fig. 25. 



As an instance of this, let us consider the case of conductor A 

 (Fig. 25), charged with a quantity M 1 of electricity, and situate 

 inside a closed conductor B kept at a constant potential V 2 . 



Equilibrium being established, let us fix the electrical masses on 

 A and B and introduce into the interval a dielectric layer C, of 

 inductive capacity /*, the internal and external surfaces of which, 

 S and S', are equipotential surfaces belonging to the primitive 

 system, where the potentials were respectively V and V. It is easy 

 to see that equilibrium is not disturbed when we distribute on 

 the surfaces S and S' electrical charges, M and + M, identical with 



