Question

Point charge $+4q$, $-q$ and $+4q$ are kept on the x-axis at points $x=0,x=a$ and $x=4a$ respectively. Then:

• A. Only -q is in stable equilibrium
• B. None of the charges are in equilibrium.
• C. All the charges are in unstable equilibrium.
• D. All the charges are in stable equilibrium.

Answer 1

The correct option is C All the charges are in unstable equilibrium.

At the present position all the charges are in equilibrium. But when
they displaced slightly from their present position, they do not return
back. So, they are in unstable equilibrium position.