Question

A dipole of dipole moment $p$ is rotated by angle $\pi$ in a uniform electric field of strength $E$. The work required.

• A. must be $pE$
• B. must be $2pE$
• C. must be zero
• D. may be zero

Answer 1

Answer: (D)

may be zero

work required = - change in potential energy$=-PEcos(\theta +\pi )-(-PEcos\theta )=2PEcos\theta$

depending on $\theta$ value of work required can be zero