Question

Two point charges + 8 q 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 charge is zero is -

• A. 2 L
• B. L/4
• C. 8 L
• D. 4 L

Answer 1

The correct option is A 2 L

$E_1=\frac{K\left(8q\right)}{(l+d{)}^2}$

$E_2=\frac{K(-2q)}{d^2}$

$E_{net}=E_1+E_2=0$

$=\frac{K\left(8q\right)}{(l+d{)}^2}-\frac{K\left(2q\right)}{d^2}=0$

$\Rightarrow \frac{4}{(l+d{)}^2}=\frac{1}{d^2}\Rightarrow 2d=d+l$

Position of point is $x=d+l=2l$