Question

Find the distance of the point from $A,$ where the net electric field will be zero for the given configuration.

• A. $\frac{5}{3}\text{m}$ towards right
• B. $\frac{1}{3}\text{m}$ towards right
• C. $\frac{4}{3}\text{m}$ towards right
• D. $\frac{2}{3}\text{m}$ towards right

Answer 1

The correct option is C $\frac{4}{3}\text{m}$ towards right

Let the electric field is zero at a distance $x$ from $A$ and in between $A\&B$
Electric field due to charge $A$ is $\frac{Kq}{x^2}=\frac{4K}{x^2}$
Electric field due to charge $B$ is $\frac{Kq}{(4-x{)}^2}=\frac{16K}{(4-x{)}^2}$
For net electric field to be zero,
$\frac{4K}{x^2}=\frac{16K}{(4-x{)}^2}$
$\frac{4-x}{x}=\pm 2$
$4-x=\pm 2x$
$4=3x\text{or}4=-x$
$x=\frac{4}{3}\text{m or}-4\text{m}$

Hence, option (c) is correct.