ELECTRIC POTENTIAL. 11 



electric potential of the sealing-wax would equal one- 

 eighth of a foot-pound. 



If only half this energy were required to overcome 

 inertia and friction, the other half might be expended in 

 lifting to a height of one foot an ounce weight attached 

 to a thread fastened to the end of the rod, and passing 

 over a pulley. In which case the work accomplished 

 by this half would be represented by one-sixteenth of 

 a foot-pound. Or the weight might be raised, or other 

 work to the same amount accomplished, by putting in 

 motion light machinery connected with the rod by gear- 

 ing at its center ; the added friction being included in 

 the ounce representing friction and inertia. 



Repulsion would evidently produce the same results 

 in this case as attraction. 



To distinguish between electricity and electric poten- 

 tial, we must bear in mind that electricity represents 

 the energy itself, while potential represents certain rela- 

 tions between this energy and matter. Hence we derive 

 the following definition : 



Electric potential is the power which a body possesses to 

 accomplish work by virtue of its electricity. 



DIFFERENCE OF POTENTIAL. To accomplish work 

 in this way there must first be a difference of po- 

 tential. 



The descending weight could not raise the other 

 weight unless there was a difference of level between 

 them. The heated metal could not heat a similar mass 

 unless there was a difference of temperature between 

 them. Neither could the electrified sealing-wax attract 

 the rod unless there was a difference of electric energy 

 between them. And these phrases, difference of level, 

 difference of temperature, difference of electric energy, 



