Question

Two equal positive point charges are separated by a distance $2 a$. The distance of a point from the centre of the line joining two charges on the equatorial line (perpendicular bisector) at which force experienced by a test charge $q_0$ becomes maximum is $\frac{a}{\sqrt{x}}$. The value of $x$ is ______

Answer 1

$F=\frac{2 K q q_0 x}{\left(x^2+a^2\right)^{3 / 2}}$
For $F$ to be maximum
$\frac{ d F}{ d x}=0 $
$x=\frac{a}{\sqrt{2}}$