Question

Three charges are placed along $x$-axis at $x=-a,x=0$ and $x=a$ as shown in the figure. The potential energy of the system is

• A. $-\left(\frac{1}{4\pi {\epsilon }_0}\right)\frac{q^2}{a}$
• B. $-\left(\frac{1}{4\pi {\epsilon }_0}\right)\frac{3q^2}{2a}$
• C. $+\left(\frac{1}{4\pi {\epsilon }_0}\right)\frac{q^2}{a}$
• D. $+\left(\frac{1}{4\pi {\epsilon }_0}\right)\frac{3q^2}{2a}$

Answer 1

Answer: (B)

$U=\frac{-k{q}^2}{a}-\frac{k{q}^2}{a}+\frac{k{a}^2}{2a}$
$U=\frac{-3k{q}^2}{2a}$