Question

what is work in moving a dipole from 30° to 60° in an external field E

Answer 1

Given dipole of dipole moment p in an electric field E. It is rotated from θ

1

to θ

2

. We have to find the work done by external force.

When a dipole of dipole moment p is placed in electric field, work done in rotated the dipole by angle θ is

W=−pEcosθ

1

Now work done in rotating dipole by θ

1

is

W

2

=−pEcosθ

2

Work done in rotating the dipole from θ

1

to θ

2

is

W=W

2

−W

1

=−pEcosθ

2

−(−pEcosθ

1

)

=pE(cosθ

1

−cosθ

2

)