Q 12-01-005NEETNEET 2023Top questionEasy
An electric dipole is placed at an angle of $30°$ with an electric field of intensity $2 \times 10^5\ \text{N C}^{-1}$. It experiences a torque equal to $4$ N m. Calculate the magnitude of charge on the dipole, if the dipole length is $2$ cm.
Answer: (D) $2$ mC
Concept. Torque on a dipole: $\tau = pE\sin\theta$ with $p = q \times$ (dipole length).
Step 1. Substitute.
$$4 = q \times 0.02 \times 2 \times 10^5 \times \frac12 = 2000q$$
Step 2. Charge. $q = 2 \times 10^{-3}$ C $= 2$ mC.
Answer. $2$ mC (Option D).
Solution by Sreeraj P, M.Sc Physics