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NEET 2012 (AIPMT, Prelims) · Electric Dipole

Electric Dipole question from NEET 2012 (AIPMT, Prelims)

Q73NEET 2012 · AIPMT · PRELIMSEasy

Electric Dipole

An electric dipole of moment p is placed in an electric field of intensity E. The dipole acquires a position such that the axis of the dipole makes an angle θ\theta with the direction of the field. Assuming that the potential energy of the dipole to be zero when θ\theta = 90o, the torque and the potential energy of the dipole will respectively be

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Answer: (a)

  1. Torque: τ=pEsin⁡θ\tau = pE\sin\theta.
  2. With U=0U = 0 at θ=90∘\theta = 90^\circ: U=−∫90∘θτ dθU = -\int_{90^\circ}^{\theta}\tau\,d\theta gives U=−pEcos⁡θU = -pE\cos\theta.
  3. So the answer is (a) pEsin⁡θ, −pEcos⁡θpE\sin\theta,\ -pE\cos\theta.
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