Question

Two point charges $+8q$ and $-2q$ are located at $x=0$ and $x=L$ respectively. The location of a point on the x axis at which the net electric field due to these two point charges is zero is :

• A. $\frac{L}{4}$
• B. $2L$
• C. $4L$
• D. $8L$

Answer 1

The correct option is B $2L$

The net electric field at P is

$E=k\frac{8q}{x^2}+k\frac{(-2q)}{(x-L{)}^2}=0$

$\Rightarrow \frac{4}{x^2}=\frac{1}{(x-L{)}^2}$

$\Rightarrow \frac{2}{x}=\frac{1}{(x-L)}$

or $x=2x-2L\Rightarrow x=2L$