An electric dipole is placed at a distance of 2 cm from an infinite plane sheet having positive charge density . Choose the correct option from the following.
- (A)Torque on dipole is zero and net force is directed away from the sheet.
- (B)Torque on dipole is zero and net force acts towards the sheet.
- (C)Potential energy of dipole is minimum and torque is zero.✓ Correct
- (D)Potential energy and torque both are maximum
Answer: (C)
Solution
An infinite plane sheet of uniform positive surface charge density produces a field of constant magnitude
directed away from the sheet everywhere, independent of distance.
Because the field is uniform, the force on each end of the dipole is equal and opposite regardless of orientation, so the net force on the dipole is always zero.
With closer to the sheet and farther from it (as shown), the dipole moment points away from the sheet — the same direction as . The torque is
since and are parallel.
The potential energy is
which is minimized at — exactly the orientation shown.
The potential energy of the dipole is minimum and the torque on it is zero.
directed away from the sheet everywhere, independent of distance.
Because the field is uniform, the force on each end of the dipole is equal and opposite regardless of orientation, so the net force on the dipole is always zero.
With closer to the sheet and farther from it (as shown), the dipole moment points away from the sheet — the same direction as . The torque is
since and are parallel.
The potential energy is
which is minimized at — exactly the orientation shown.
The potential energy of the dipole is minimum and the torque on it is zero.
JEE Main · 2025 · 29 Jan 2025 · Shift 2 · Single correct option