Q.
The work required to put the four charges at the corners of a square of side a, as shown in figure, is
A) $\frac{1}{4\pi\varepsilon_{0}}\ \frac{q^{2}}{a}$
B) $- \frac{2.6}{4\pi\varepsilon_{0}}\frac{q^{2}}{a}$
C) $+ \frac{2.6}{4\pi\varepsilon_{0}}\frac{q^{2}}{a}$
D) None of these
Explanation
(b) Work done =potential energy of configuration of charges
$\frac{1}{4\pi\varepsilon_{0}a}\lbrack q\left( - q) + (9 - q)q + q( - q) + ( - q)(q) \right\rbrack + \frac{( - q)( - q) + q^{2}}{4\pi\varepsilon_{0}a\sqrt{2}}$
$= \frac{1}{4\pi\varepsilon_{0}}\left\lbrack - \frac{4q^{2}}{a} + \frac{2q^{2}}{a\sqrt{2}} \right\rbrack = - \frac{2.6}{4\pi\varepsilon_{0}}\frac{q^{2}}{a}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.