Electrostatics Part 3

In the first configuration (1 ) as shown in the figure, four identical charges (q0) are kept at the corners A, B,C and D of square of side length ' a '. In the second configuration (2 ), the same charges are shifted to mid points G,E,H and F, of the square.

If K=‌

1

4πε0

, the difference between the potential energies of configuration (2 ) and (1 ) is given by