Question

An electric dipole with dipole moment \( 5 \times 10^{-7} \, \text{Cm} \) is in an electric field of \( 2 \times 10^4 \, \text{NC}^{-1} \) at an angle of \( 60^\circ \) with the direction of the field. The torque acting on the dipole is:

• A. \( 9 \times 10^{-3} \, \text{Nm} \)
• B. \( 1 \times 10^{-4} \, \text{Nm} \)
• C. \( 8.66 \times 10^{-3} \, \text{Nm} \)
• D. \( 2.88 \times 10^{-3} \, \text{Nm} \)

Hint:

Use \( \tau = pE \sin\theta \) for torque on dipole in uniform electric field.

Answer 1

The Correct Option is C

Torque on dipole: \[ \tau = pE \sin\theta = (5 \times 10^{-7}) \cdot (2 \times 10^4) \cdot \sin 60^\circ = (1 \times 10^{-2}) \cdot \frac{\sqrt{3}}{2} \approx 8.66 \times 10^{-3} \, \text{Nm} \]