An electric dipole of dipole moment 4 × 10−9 Cm is placed in a uniform electric field of magnitude of 5 × 104 N/C. The torque of 10−4 Nm acts on it. The angle between the dipole moment and the electric field is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 30°
A dipole in a uniform electric field experiences a torque that depends on the angle between the dipole moment and the field:
\( \tau = pE\sin\theta \)
\( \displaystyle \sin\theta = \frac{\tau}{pE} \)
\( \displaystyle \sin\theta = \frac{10^{-4}\,\mathrm{N\,m}}{4\times10^{-9}\,\mathrm{C\,m} \times 5\times10^{4}\,\mathrm{N\,C^{-1}}} \)
\( \displaystyle \sin\theta = \frac{10^{-4}}{2\times10^{-4}} = \frac{1}{2} \)
\( \theta = 30^\circ \)