In the first configuration (1) as shown in the figure, four identical charges ( q_0) are kept at the corners A, B, C and D of square of side length…

In the first configuration ($\displaystyle 1$) as shown in the figure, four identical charges $\displaystyle \left(\mathrm{q}_0\right)$ are kept at the corners A, B, C and D of square of side length 'a'. In the second configuration ($\displaystyle 2$), the same charges are shifted to mid points G, E, H and F, of the square. If K = $\displaystyle \frac{1}{4 \pi \epsilon_0}$, the difference between the potential energies of configuration ($\displaystyle 2$) and ($\displaystyle 1$) is given by :