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 $\frac{\sqrt{2}}{\sqrt{2}}=1\, m$

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