Question

A dipole with dipole moment P is aligned with uniform external electric field E. The work done by an external agent to rotate the dipole by 180° so that finally dipole moment is opposite to the electric field E is

PE

2PE



Zero

Answer 1

Answer:

Work done in rotating the dipole through an angle 180 W=2pE

Answer 2

Given:

A dipole with dipole moment P is aligned with uniform external electric field E.

To find:

Total work done to rotate the dipole by 180°?

Calculation:

• The net work done to rotate the dipole can be calculated as the change in potential energy due to change in arrangement of the dipole.

$W = - \Delta Energy$

$\implies W = Energy1 - Energy2$

$\implies W = PE \cos( {0}^{ \circ} ) - PE \cos( {180}^{ \circ} )$

$\implies W = PE (1 ) -PE ( - 1)$

$\implies W = PE + PE$

$\implies W = 2PE$

So, net work done is 2PE.

• P is dipole moment
• E is Electrostatic Field Intensity

This calculation can also be done with calculus!