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प्रश्न
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, find the work required to be done by an external agent.
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उत्तर
When the dipole is aligned parallel to the field, θ0 = 0°
When the dipole is aligned antiparallel to the field, θ = 180°
∴ Work is done by an external torque,
W = pE [cos θ0 - cos θ]
= pE[cos 0 - cos 180]
= pE [1 - (-1)] = 2 pE
Work required to be done by an external agent is 2 pE.
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