An electric dipole with dipole moment Cm is aligned with the direction of a uniform electric field of magnitude N/C. The dipole is then rotated through an angle of with respect to the electric field. The change in the potential energy of the dipole is:

NEET UGPhysicsModerateNEET 2025

An electric dipole with dipole moment $5 \times 10^{-6}$ Cm is aligned with the direction of a uniform electric field of magnitude $4 \times 10^5$ N/C. The dipole is then rotated through an angle of $60^{\circ}$ with respect to the electric field. The change in the potential energy of the dipole is:

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Sol. Given

|\vec{P}| = 5 \times 10^{-6}

C m

|\vec{E}| = 4 \times 10^5

N/C

\theta_i = 0^\circ

and

\theta_f = 60^\circ

\Delta U = U_f - U_i

= -PE\cos\theta_f + PE\cos\theta_i

= PE(\cos\theta_i - \cos\theta_f)

= 5 \times 10^{-6} \times 4 \times 10^5 \left[1 - \frac{1}{2}\right]

= 10 \times 10^{-6} \times 10^5 = 1

Source: geekyrakshit/indian-exam-questions / neet2025-code45

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