Question

At what angle θ between the dipole moment and the electric field is the torque on the dipole maximum?

Options

• θ = 0°

• θ = 180°

• θ = 90°

• θ = 45°

Answer 1

The magnitude of torque is τ = pE sin θ. Since sin θ reaches its maximum value of 1 when θ = 90°, the maximum torque is τ_max = pE. This occurs when the dipole moment is perpendicular to the electric field direction.