# Calculate the potential energy of the system shown in figure

$(a)\;\large\frac{k\;q^2}{a}\qquad(b)\;-\large\frac{k\;q^2}{a}\qquad(c)\;\sqrt{2} \large\frac{k\;q^2}{a}\qquad(d)\;-\sqrt{2} \large\frac{k\;q^2}{a}$

Answer : (a) $\;-\sqrt{2} \large\frac{k\;q^2}{a}$
Explanation :
$P . E \;of\;system = \large\frac{2\;k\;q^2}{a}- \large\frac{2\;k\;q^2}{a}- \large\frac{2\;k\;q^2}{\sqrt{2} a}$
$=-\large\frac{\sqrt{2}\;k\;q^2}{2}\;.$