Q. Two equal charges $q$ are placed at a distance of $2a$ and a third charge $- 2q$ is placed at the midpoint. The potential energy of the system is
A) $\frac{q^{2}}{8\pi\varepsilon_{0}a}$
B) $\frac{{6q}^{2}}{8\pi\varepsilon_{0}a}$
C) $- \frac{{7q}^{2}}{8\pi\varepsilon_{0}a}$
D) $\frac{{9q}^{2}}{8\pi\varepsilon_{0}a}$
Explanation
(c) $U_{system} = \frac{1}{4\pi\varepsilon_{0}}\frac{(q)( - 2q)}{a} + \frac{1}{4\pi\varepsilon_{0}}\frac{( - 2q)(q)}{a} + \frac{1}{4\pi\varepsilon_{0}}\frac{(q)(q)}{2a}$
$U_{system} = - \frac{7\ q^{2}}{8\pi\varepsilon_{0}a}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.