Question

Electric charges of $+10\mu C,+5\mu C,-3\mu C$ and $+8\mu C$ are placed at the corners of a square of side $\sqrt{2}m$. The potential at the centre of the square is

• A. 1.8 V
• B. $1.8\times 10^{6}V$
• C. $1.8\times 10^{5}V$
• D. $1.8\times 10^{4}V$

Answer 1

Answer: (C)

Length of each side of square is $\sqrt{2}m$, so distance of
its centre from each corner is $\frac{\sqrt{2}}{\sqrt{2}}=1m$

Potential at the centre,
$V=9\times 10^9\left[\frac{10\times 10^{-6}}{1}+\frac{5\times 10^{-6}}{1}-\frac{3\times 10^{-6}}{1}+\frac{8\times 10^{-6}}{1}\right]$
$=1.8\times 10^{5}V$