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An electric dipole of moment p⃗ is placed in an electric field of intensity E⃗. The dipole acquires a position such that the axis of the dipole makes an angle θ with the direction of the field. Assuming that the potential energy of the dipole to be zero when θ = 90°, the torque and the potential energy of the dipole will respectively be:
- pE sin θ, −pE cos θ
- pE sin θ, −2pE cos θ
- pE sin θ, 2pE cos θ
- pE cos θ, −pE cos θ
Correct answer: pE sin θ, −pE cos θ
Solution
The torque on a dipole in an electric field is given by τ = pE sin θ, and the potential energy is U = -pE cos θ, with the reference point of zero potential energy at θ = 90°. Thus, the correct answer is option A.
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