Q. A molecule with a dipole moment $p$ is placed in an electric field of strength $E.$ Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency is
A) $- 2\ pE$
B) $- pE$
C) $pE$
D) $2\ pE$
Explanation
(d) $W = PE\left( 1 - \cos\theta \right)\ here\ \theta = 180{^\circ}$
$\therefore W = - PE{(1 - cos}{180{^\circ}}) = PE\lbrack 1 - ( - 1)\rbrack = 2PE$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.