Question

Two charges + q and -q are placed at a distance a in a uniform electric field. The dipole moment of the combination is $2qa(cos\theta \hat{i}+sin\theta \hat{j})$, where, $\theta$ is the angle between the direction of the field and the line joining the charges.
Which of the following statement(s) is / are correct?

• A. The torque exerted by the field on the dipole vanishes
• B. The net force on the dipole vanishes
• C. The torque is independent of the choice of coordinates
• D. The net force is independent of a

Answer 1

Answer: (B), (C), (D)

The correct options are
B The net force is independent of a
C The torque is independent of the choice of coordinates
D The net force on the dipole vanishes

The situation can be diagrammatically as,
The dipole moment,
$P=2qa(cos\theta \hat{i}+sin\theta \hat{j})$
The net force on the dipole is always zero while net torque on the dipole is not zero.