Question

When a dipole is anti-aligned with the external electric field (θ = 180°), the potential energy is:

Options

• -pE (minimum)

• 0

• +pE (maximum)

• pE/2

Answer 1

When the dipole is anti-aligned (θ = 180°), we have \[\cos(180°) = -1\], so \[U = -pE \times (-1) = +pE\]. This is the maximum potential energy, representing an unstable equilibrium. Any small perturbation will cause the dipole to rotate away from this configuration.