Question

Two charges of $10\mu C\text{and}-20\mu C$ are separated by a distance of $20\text{cm}$. The distance of the point from $10\mu C$ where electric potential is zero, if it lies between them is

• A. $\frac{3}{20}$ cm
  
• B. $6.67$ cm
• C. $10$ cm
• D. $16$ cm

Answer 1

The correct option is B $6.67$ cm

Let $x$ be the distance form $10\mu C$ where potential is zero.
$\Rightarrow 0=\frac{k\left(10\mu C\right)}{x}+\frac{k(-20\mu C)}{20-x}$
$\Rightarrow 0=\frac{10}{x}-\frac{20}{20-x}$
$\Rightarrow (20-x)10=20x$
$\Rightarrow 20=3x$
$x=\frac{20}{3}=6.67\text{cm}$