Q. Three particles, each having a charge of $10\mu C$ are placed at the corners of an equilateral of side $10cm$, the corners of an equilateral triangle of side $10\ cm$. The electrostatic potential energy of the system is (Given $\frac{1}{4\pi\varepsilon_{0}} = 9 \times 10^{9}N - m^{2}/C^{2\ })$

A) Zero
B) Infinite
C) $27\ J$
D) $100\ J$
Explanation

(c) For pair of change $U = \frac{1}{4\pi\varepsilon_{0}}.\frac{q_{1}q_{2}}{r}$
$U_{system} = \frac{1}{4\pi\varepsilon_{0}}\ \left\lbrack \frac{10 \times 10^{- 6} \times 10 \times 10^{- 6}}{10/100} \right.\ $
$\left. \ + \frac{10 \times 10^{- 6} \times 10 \times 10^{- 6}}{10/100} + \frac{10 \times 10^{- 6} \times 10 \times 10^{- 6}}{10/100} \right\rbrack$
$= 3 \times 9 \times 10^{9} \times \frac{100 \times 10^{- 12} \times 100}{10} = 27J$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.