The magnitude of torque acting on an electric dipole when placed at right angles to a uniform electric field is $2 \sqrt{2} \times 10^{-2}$ Nm. Magnitude of the torque acting on the dipole when dipole moment makes 45° with electric field will be:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $2 \times 10^{-2}$ Nm
The torque on an electric dipole is -
$τ=pE\sin θ$
Case 1: $θ=90°$
$τ=pE\sin 90°=2\sqrt{2}×10^{-2}Nm$
$⇒pE-2\sqrt{2}×10^{-2}Nm$
Case 2: $θ=45°$
$τ=pE\sin 45°=pE×\frac{1}{\sqrt{2}}$
$⇒pE×\frac{1}{\sqrt{2}}=\frac{1}{\sqrt{2}}×10^{-2}Nm$
$τ=2×10^{-2}Nm$