Question

A dipole of charge 0.01C and separation 0.4mm, is placed in an electric field of strength 10 dyne/CC , Find the maximum torque exerted on the dipole in the field.

• A. 4 x 10-9 Nm
• B. 2 x 10-10 Nm
• C. 4 x 10-10 Nm
• D. 2 x 10-9 Nm

Answer 1

Answer: (C)

4 x 10-10 Nm

Answer 2

The correct option is (C): 4 x 10-10 Nm

P=0.01$\times$0.4$\times$10-3=4$\times$10-6 cm

E=10$\times$10-5N

$|\tau|=|\vec{P}\times \vec{E}|=4\times10^{-6}\times10\times10^{-5}$

$=4\times10^{-10}$Nm