Question

Which equilibrium position of a dipole in a uniform electric field is stable?

Options

• When θ = 90°

• When θ = 0° (parallel)

• When θ = 180° (anti-parallel)

• When θ = 45°

Answer 1

At θ = 0° (parallel alignment), the potential energy is minimum (U = -pE), and the equilibrium is stable. If the dipole is slightly rotated from this position, a restoring torque acts to bring it back to alignment. This is analogous to a ball at the bottom of a valley, which returns to its position when slightly displaced.