upon a unit of positive electricity in bringing it up to 

 that point from an infinite distance. Had the charge on 

 A been a charge, the force would have been one of 

 attraction, in which case we should have theoretically to 

 measure the potential at P, either by the opposite 

 process of placing there a + unit, and then removing it 

 to an infinite distance against the attractive forces, or 

 else by measuring the amount of work which 'would be 

 done by a + unit in being attracted up to P from an 

 infinite distance. 



It can be shown that where there are more electrified 

 bodies than one to be considered, the potential due to 

 them at any point is the sum of the potentials (at that 

 point) of each one taken separately. 



238. It can also be shown that the potential at a 

 point P, near an electrified particle A, is equal to the 

 quantity of electricity at A divided by the distance 

 between A and P. Or, if the quantity be called q, and 



the distance r, the potential is X* If there are a 

 number of electrified particles at different distances 

 from P, the separate values of the potential 1. due to 



each electrified particle separately can be found x and 

 therefore the potential at P can be found by dividi^ the 

 quantity of each charge by its distance from the point P, 

 and then adding ^lp together the separate amounts so 

 obtained. The symbol V is generally used to represent 

 potential. The potential at point P we will call V P , then 



or V P = 2f. 

 r 



This expression 2 represents the work done on or 



* The complete proof would require an elementary application of the 

 integral calculus, but an easy geometrical demonstration, sufficient for 

 present purposes, is given below. 



