The electric field of a positive charge is radially outwards, with its potential being positive everywhere. This potential decreases along the electric field direction and increases opposite to it. Consider a positive test charge placed in this electric field, which moves from the initial position of A to the final position of B. Electric force does positive work on the test charge, and the electric potential of point B is lower than that at point A. If the electric field is known then the potential of the system can be calculated. This expression gives the unit of an electric field as volt per meter. Alternatively, if a test charge moves away from a negative static charge, then the electric potential of the test charge increases. Consider a charge having the magnitude of electronic charge, moving in a potential difference of 1 volt, then the change in the potential energy is defined as 1 electron volt. If the moving charge is a multiple of e, then the change in energy is a multiple of 1 eV.