An iron needle is kept near a strong bar magnet. It will experience:
- (A)A force of attraction and no torque
- (B)A force of attraction and a torque✓ Correct
- (C)A torque and no force
- (D)Neither a force nor a torque
Answer: (B)
Solution
A soft-iron needle is ferromagnetic, so near a bar magnet it becomes magnetised and behaves like a magnetic dipole.
The bar magnet's field is non-uniform, so the two induced poles of the needle feel unequal forces, giving a net force of attraction towards the magnet.
The induced dipole also tends to align with the field, so it experiences a torque. Hence the needle feels both a force and a torque.
The bar magnet's field is non-uniform, so the two induced poles of the needle feel unequal forces, giving a net force of attraction towards the magnet.
The induced dipole also tends to align with the field, so it experiences a torque. Hence the needle feels both a force and a torque.
CBSE Class 12 Board · 2024 · Single correct option