Question

Charge $5\mu C,-2\mu C,3\mu C$ and $-9\mu C$ are placed on a square ABCD of side $1$ cm. The net electric potential at the centre is:

• A. $-27KV$
• B. $-27\sqrt{2}\times {10}^{5}V$
• C. $-9KV$
• D. $0V$
  

Answer 1

The correct option is B $-27\sqrt{2}\times {10}^{5}V$

Each change along the various is separated

from the enters O by distance, $r=\frac{a}{\sqrt{2}}$

so, $r=\frac{1}{\sqrt{2}}cm=\frac{1}{\sqrt{2}}\times {10}^{-2}m$

so potential at O,

$v=\frac{k}{r}\sum q=\frac{9\times {10}^4}{\frac{1}{\sqrt{2}}\times {10}^{-2}}\times (5-2-9+3)\times {10}^{-6}=(-)27\sqrt{2}\times {10}^{5}v$