Resultant Electrical Force

The resultant electrical force at a point is the force which -would be exerted on a very small body charged with unit quantity of positive electricity placed at the point, it being supposed that the presence of the body does not disturb the electrification of the rest of the system.

Hence if R be the resultant electrical force at a point, and e the number of units of electricity at that point, the force acting on the body thus charged is Re.

If the body so charged be moved by the forces acting on it, work is done.