HETEROGENEOUS LINEAR CONDUCTORS. 197 



Let us now suppose that a closed circuit is composed of separate 



conductors A, B, C L (Fig. 54) comprising bodies of Volta's 



second class that is to say, that the chain of conductors does not 

 obey the law of tensions; the circuit will be traversed by a per- 

 manent current. 



Fig. 54- 



Let r^ r^Tf. *j, be the resistances of the different conductors, 



V and V'a, V ft and V' & the successive potentials at the ends of 



each going in the direction of the current, and in like manner let 



H a6 , H &c Hj a be the successive electromotive forces of contact ; 



we have 



H..-V.-V,, 



The current being the same throughout the whole extent of the 

 circuit, we have also 



from which, reducing, we get 



The numerator of this fraction represents the algebraical sum 

 of the electromotive forces of contact in the chain of con- 

 ductors; it is the electromotive force E of the circuit The 



