Question

A dipole is placed in an electric field whose direction is fixed but its magnitude varies with distance. It is possible that the dipole experiences :

• A. no net force and no torque
• B. a net force but no torque
• C. a net force and a torque
• D. no net force but a torque

Answer 1

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

The correct options are
B a net force but no torque
C a net force and a torque
D no net force but a torque

Dipole means two charges $+q$ and $-q$ are placed at a certain distance.
There three cases may be occured for electric field whose direction is fixed but magnitude varies with distance.
1) when forces on the two charges are in different direction and different magnitude, they will have a net force and a torque.
2) when forces on the two charges are in same direction but different magnitude, they will have a net force but no torque.
3) when forces on the two charges are in opposite direction but same magnitude, they will have no net force but a torque.