Question

What must an external agent do to rotate a dipole slowly in a uniform electric field?

Options

• Apply a constant force equal to pE

• Apply a torque equal to twice the field torque

• Apply no torque since the dipole rotates freely

• Apply a torque that balances the field torque in magnitude

Answer 1

To rotate the dipole slowly (quasi-statically), the external torque must exactly balance the electric field torque at each instant. This prevents acceleration and ensures that the work done by the external agent is stored entirely as potential energy rather than kinetic energy.