An electric dipole of dipole moment p is aligned parallel to a uniform electric field E. The energy required to rotate the dipole by 90⁰ is

Options

(a) p E²
(b) p² E
(c) p E
(d) infinity

Correct Answer:

p E

Explanation:

When electric dipole is aligned parallel θ = 0⁰ and the dipole is rotated by 90⁰ i.e., θ = 90⁰
Energy required to rotate the dipole W = Uⱼ – Uᵢ = (- pE cos 90⁰) – ( – pE cos 0⁰) = p E