question_answer

                Torque acting on electric dipole of dipole moment \[\vec{p}\] placed in uniform electric field \[\vec{E}\] is:

A)                                                                                                                                                                                                            \[\vec{p}\times \vec{E}\]

B)                 \[\vec{p}\,.\,\vec{E}\]                  

C)                 \[\vec{p}\times \vec{E}\times \vec{p}\]              

D)                 \[\frac{\vec{E}\,.\,\vec{p}}{{{p}^{2}}}\]

Correct Answer: A

Solution :

                          If electric dipole is placed perpendicular to electric field, in this case net force on dipole will be zero but torque on dipole will not be zero.                                 Torque \[\tau =pE\sin \theta \]                         \[or\vec{\tau }=\vec{p}\times \vec{E}\]