Question

Two electric charges $12\mu C$ and $-6\mu C$ are placed $20cm$ apart in air. There will be a point P, at which electric potential is zero on the line joining these two charges and outside excluding the region between them. The distance of P from $-6\mu C$ charge is:

• A. $0.1m$
• B. $0.15m$
• C. $0.2m$
• D. $0.25m$

Answer 1

Answer: (C)

$0.2m$

Let P be at distance $x$ from $-6\mu C$ charge.
We know, potential $V=\frac{kq}{r}$
Given, potential at P: $V_P=0$

$\Rightarrow \frac{k\times 12\times {10}^{-6}}{(0.2+x)}+\frac{k\times (-6)\times {10}^{-6}}{x}=0$

or, $\frac{12}{0.2+x}=\frac{6}{x}$

or, $2x=0.2+x$

or, $x=0.2m$