Question

Define electric potential energy of a system of two charges and find an expression for it.

Answer 1

Electric potential energy, or electrostatic potential energy, is a potential energy(measured in joules) that results from conservative Coulomb forces and is associated with the configuration of a particular set of point charges within a defined system. An object may have electric potential energy by virtue of two key elements: its own electric charge and its relative position to other electrically charged objects.
Electric potential when q1 is placed: V (~r2) .= V2 = k q1 r12
Electric potential energy when q2 is placed into potential V2: U = q2V2 = k q1q2
r12
Electric potential when q2 is placed: V (~r1) .= V1 = k q2 r12
Electric potential energy when q1 is placed into potential V1: U = q1V1 = k q1q2
r12.
#2 Electric potential energy of q1 and q2:
U = 12 X2
i=1
qiVi,
where V1 = k q2
r12
, V2 = k q1
r12

Answer 2

Explanation:

Electrostatic potential energy of a system of charges is defined as the work done to move the charges from infinity to their present configuration. Read more on Sarthaks.com - https://www.sarthaks.com/424904/define-electrostatic-potential-energy-of-a-system-of-charges