Question

How does the potential energy of a dipole change as it rotates from being antiparallel (θ = 180°) to being parallel (θ = 0°) with the electric field?

Options

• The potential energy increases from -pE to pE

• The potential energy decreases from pE to -pE

• The potential energy first increases then decreases

• The potential energy remains constant at zero

Answer 1

At θ = 180°: U = -pE cos 180° = -pE(-1) = pE. At θ = 0°: U = -pE cos 0° = -pE(1) = -pE. The potential energy decreases by 2pE as the dipole rotates from antiparallel to parallel alignment. This decrease represents the conversion of potential energy to kinetic energy during the rotation.