Question

Two point charges each of charge $+q$ are fixed at $(+a,0)$ and $(-a,0)$. Another positive point charge $q$ placed at the origin is free to move along x-axis. The charge $q$ at the origin in equilibrium will have:

• A. maximum force and minimum potential energy
• B. minimum force and maximum potential energy
• C. maximum force and maximum potential energy
• D. minimum force and minimum potential energy

Answer 1

The correct option is B minimum force and maximum potential energy

Force on q

=$\frac{K{q}^2}{a^2}\hat{i}-\frac{K{q}^2}{a^2}\hat{i}=0$

potential energy

$=\frac{K{q}^2}{a}\hat{i}+\frac{K{q}^2}{a}\hat{i}=\frac{2K{q}^2}{a}$

So at the origin the force is minimum and potential energy is maximum . so the correct answe is B.