Question

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

• A. 0.10 m
• B. 0.15 m
• C. 0.20 m
• D. 0.25 m

Answer 1

Answer: (C)

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, $x=0.2m$