Question

A certain charge Q is divided into two parts q and (Q - q). How should the charges Q and q be divided so that q and (Q - q) placed at a certain distance apart experience maximum electrostatic repulsion?

Options

• `Q = q/2`

• Q = 3q

• Q = 2q

• Q = 4q

Answer 1

Q = 2q

Explanation:

F = `(kq(Q - q))/r^2`

`(dF)/(dq)` = 0 for maxima and minima

`k/r^2[-2q + Q] = 0`

Now, `((df^2)/(dq^2)) < 0`

Q = 2q

As a result, for maximum force, Q = 2q.