explain the concept of electric potential energy. Derive an expression for potential energy of a system of two point charges .Generalise the expression for N discrete charges.
Electrostatic potential energy of a system of point charges is the total amount of work done in bringing the various charges to their respective positions from infinitely large mutual separations.
Let us consider a point charge q1 which is held at a point P1 with position vector r1 in space. Another point charge q2 is at infinite distance from q1. This is to be brought to the position P2(r2), where P1P2=r12
​Electric potential energy at P2 due to charge q1 at P1 is
Let us consider a point charge q1 which is held at a point P1 with position vector r1 in space. Another point charge q2 is at infinite distance from q1. This is to be brought to the position P2(r2), where P1P2=r12
​Electric potential energy at P2 due to charge q1 at P1 is