If the external force is removed on reaching P, the
electric force will take the charge away from Q – the stored energy (potential
energy) at P is used to provide kinetic energy to the charge q in such a
way that the sum of the kinetic and potential energies is conserved Thus, work done by external forces in moving a charge q from R to P is
WRP =   
        =    –
 (2 1)
This work done is against electrostatic repulsive force and gets stored
as potential energy At every point in electric field, a particle with charge q possesses a
certain electrostatic potential energy, this work done increases its potential
energy by an amount equal to potential energy difference between points
R and P