Q. 4 point charges each $+ q$ is placed on the circumference of a circle of diameter $2d$ in such a way that they form a square. The potential at the centre is
A) 0
B) $\frac{4q}{d}$
C) $\frac{4d}{q}$
D) $\frac{q}{4d}$
Explanation
(b) Potential at centre due to all charges are
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$= \frac{1}{4\pi\varepsilon_{0}}\left\lbrack \frac{q}{d} + \frac{q}{d} + \frac{q}{d} + \frac{q}{d} \right\rbrack$
$= \frac{1}{4\pi\varepsilon_{0}}\frac{4q}{d}$ in S.I. unit
$= \frac{4q}{d}$ in C.G.S. unit
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.