8 ELECTROLYSIS. 



It is well to observe that there can be a manifestation of 

 electromotive force in a circuit which is brought towards or 

 away from another circuit without any difference of potential. 

 It is, according to Ampere, thus that the currents produced by 

 terrestrial magnetism should be considered. Electromotive 

 force, notwithstanding that it can be measured, and can be pro- 

 duced by a difference of potential, has therefore a more general 

 signification. 



ELECTEIC CURRENT. Whenever a metallic communication 

 is established between two insulated conductors at different 

 potentials, the equilibrium cannot subsist, the positive electricity 

 passes from the body at the higher potential towards the other, 

 a flow of electricity being produced which is designated by the 

 name of electric current. If the two bodies contain limited 

 charges, the state of equilibrium is rapidly reached, and the 

 current obtained varies with the time. But if by any means the 

 difference of potential between the two conductors is maintained 

 constant, a permanent regimen is established, and the electric 

 current is itself constant and regular. 



CURRENT INTENSITY. Electric currents are possessed of 

 different properties ; some, as the heating of conductors, chemical 

 decompositions, magnetic induction, require a transformation of 

 energy ; some others, as the action of one current upon another 

 current * or upon a magnetic pole, can be observed in a static 

 condition, that is to say without any production of work, by the 

 simple measurement of a force. 



By definition the intensity of a current in a conductor is 

 proportional to the quantity of current flowing through the 

 section of the said conductor in a unit of time. When a state 

 of stability has been established, or, otherwise, when the flow of 

 electricity is regular and constant, the intensity is the same at 

 every point of the circuit. 



Faraday and Pouillet have proved experimentally that the 

 intensity of a current is proportional to its action upon the pole 

 of a magnet or upon another constant current, which affords an 

 easy means of measuring it. 



ELECTRIC KESISTANCE. All conductors offer a resistance to 



* ' Legons sur I'e'lectrieite' et le inagnetisme,' par Mascart et Joubert. 



