The electric potential energy of a system of ‘n’ point charges is the work done to assemble this system of charges by bringing them in from an infinite distance.
If U is +ve, it indicates work is done by the external agency to assemble these charges. This work done is stored in form of potential energy. If U is -ve, it indicates work is done by the elctrostatic forces to assemble these charges. This means potential energy is released.
