Question

An electric dipole is placed in an electric field generated by a point charge. Then

• A. net electric force on the dipole must be zero
• B. net electric force on the dipole may be zero
• C. torque on the dipole due to the field must be zero
• D. torque on the dipole due to the field may be zero

Answer 1

The correct option is D torque on the dipole due to the field may be zero

The figure shows FBD of an electric dipole placed in an electric field generated by a point charge.


In any orientation,
the force on $+q$ is directed to right and on $-q$ is to left. As the electric field is non-uniform. Therefore, magnitude of forces are not equal because it depends upon strength of electric field. Hence, net force is not equal to zero.
In this orientation, clockwise torques about $O$ will be developed by the forces $F_1$ and $F_2$. Hence, net torque is not equal to zero.

But when orientation of dipole is radial as shown in figure, the forces on $+q$ and $-q$ passes through $O$, hence, no torque will be developed. Therefore, net torque will be zero.


So, the appropriate correct option is $\left(d\right)$.