An electric dipole is placed in an external uniform electric field E at an angle θ to the field. The torque experienced by the dipole will be maximum when
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → θ = π/2
The torque on a dipole in a uniform field is \( \vec{\tau} = \vec{p} \times \vec{E} \), with magnitude \( \tau = pE\sin\theta \). It is largest when \( \sin\theta = 1 \).
\( \displaystyle \tau_{\max} = pE \quad \text{at} \quad \theta = \frac{\pi}{2} \)
NCERT (2026-27):
Dipole in a Uniform External Field – “… However, the charges are separated, so the forces act at different points, resulting in a torque on the dipole. … Magnitude of torque
\( \displaystyle = qE \times 2a\sin\theta = 2qaE\sin\theta \)
… This torque will tend to align the dipole with the field E. When p is aligned with E, the torque is zero.”