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Given: Dipole moment of the dipole = p and uniform electric field = E. We know that dipole moment (p) = q.a (where q is the charge and a is dipole length). And when a dipole of dipole moment p is placed in a uniform electric field E, then Torque (τ) = Either force × Perpendicular distance between the two forces = q.aEsinθ or τ = pE sinθ or τ = p × E (vector form).

1. λ = linear charge density; Charge on elementary portion dx = λ dx.
2. Torque on the dipole is given as τ = pE sin θ.
3. Potential energy of the dipole in the electric field is given as U = -pE cos θ.
4. Dipole moment p is placed in a uniform electric field E.

Correct answer: Torque on the dipole is given as τ = pE sin θ.

Solution

Option B is correct because the torque on a dipole in a uniform electric field is given by τ = pE sin θ, which is a standard result derived from the cross product of the dipole moment and the electric field.

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