Question

A dipole with dipole moment Pis 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 Eis PE 2PE (PE)/2 Zero​

Answer 1

Given:

A dipole with dipole moment Pis aligned with uniform external electric field E. The work done by an external agent to rotate the dipole by 180°.

To find:

Work done in rotation?

Calculation:

The work done in rotating the dipole will be equal and opposite to the change in potential energy of the dipole in the electrostatic field.

$\rm \: W = - \Delta E_{potential}$

$\rm \implies \: W = - (E2_{potential} - E1_{potential})$

$\rm \implies \: W = E1_{potential} - E2_{potential}$

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

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

$\rm \implies \: W = PE + PE$

$\rm \implies \: W = 2PE$

So , work done in rotation is 2PE .