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:

$2 \times 10^{-2}$ Nm

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: $θ=45°$

$τ=pE\sin 45°=pE×\frac{1}{\sqrt{2}}$

$⇒pE×\frac{1}{\sqrt{2}}=\frac{1}{\sqrt{2}}×10^{-2}Nm$

$τ=2×10^{-2}Nm$