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. $-\left(\frac{1}{4 \pi \varepsilon_{0}}\right) \frac{q^{2}}{a}$
• B. $-\left(\frac{1}{4 \pi \varepsilon_{0}}\right) \frac{3 q^{2}}{2 a}$
• C. $+\left(\frac{1}{4 \pi \varepsilon_{0}}\right) \frac{q^{2}}{a}$
• D. $+\left(\frac{1}{4 \pi \varepsilon_{0}}\right) \frac{3 q^{2}}{2 a}$

Answer 1

Answer: (B)

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