A magnetic needle placed in a non-uniform magnetic field experiences
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → a torque and a force
A magnetic needle is a magnetic dipole: its two poles feel equal and opposite forces only if the field at both poles is the same.
In a non-uniform field the field at the two poles differs, so the two forces do not cancel and the needle feels a net force. The forces also act along different lines, so they form a couple and turn the needle towards the field direction, giving a torque as well.
Why the other options are incorrect
Option (1) a torque but not a force — Incorrect. A torque without a net force is what a needle experiences in a uniform magnetic field.
Option (3) a force but not a torque — Incorrect. The unequal forces on the two poles also form a couple, so the needle experiences a torque unless it is already aligned with the field.
Option (4) neither a force nor a torque — Incorrect. Neither a force nor a torque would act only if there were no field at the needle.