Magnetic Dipole Moment - UNSOLVED PRACTICE SET
Chapter: Magnetism and Matter | Topic: Magnetic Dipole Moment
MAGNETIC DIPOLE MOMENT - UNSOLVED PRACTICE SET
Topic: Magnetic Dipole Moment
Multiple Choice Questions
Q1. The SI unit of magnetic dipole moment is:
- Tesla
- Weber
- Amยฒ
- N/Am
Q2. The magnetic dipole moment of a current-carrying coil is given by:
- M = I/A
- M = I ร A
- M = Iยฒ ร A
- M = A/I
Q3. When a bar magnet of magnetic moment M is cut into two equal halves along its length, the magnetic moment of each half becomes:
- M/2
- M/4
- M
- 2M
Q4. A magnetic dipole placed in a uniform magnetic field experiences:
- Only a net force
- Only a torque
- Both a net force and a torque
- Neither force nor torque
Q5. The potential energy of a magnetic dipole in a uniform magnetic field is minimum when:
- The dipole is perpendicular to the field
- The dipole is anti-parallel to the field
- The dipole is parallel to the field
- The dipole is at 45ยฐ to the field
Q6. Two identical bar magnets are placed parallel to each other with opposite poles facing. The net magnetic moment of the system is:
- Zero
- Twice that of a single magnet
- Equal to that of a single magnet
- Half that of a single magnet
Short Answer Questions
Q7. Define magnetic dipole moment. Is it a scalar or a vector quantity? What is its direction?
Q8. A circular coil of N turns, radius r, carrying current I is placed in a uniform magnetic field B. Write the expression for the torque experienced by the coil.
Q9. Why does a freely suspended magnetic dipole align itself along the direction of the magnetic field?
Q10. A bar magnet has magnetic moment M. It is bent into a semicircular shape. What happens to its magnetic moment? Explain.
Q11. Two identical bar magnets of magnetic moment M each are placed perpendicular to each other with their centres coinciding. What is the resultant magnetic moment?
Q12. Write the expression for the potential energy of a magnetic dipole placed in a uniform magnetic field. When is this energy maximum and when is it minimum?
Long Answer Questions
Q13. Derive the expression for the torque experienced by a magnetic dipole placed in a uniform magnetic field. Show that the torque is maximum when the dipole is perpendicular to the field.
Q14. Explain the behaviour of a magnetic dipole in a non-uniform magnetic field. How does this explain why a bar magnet experiences both translational and rotational motion in such a field?
Q15. A bar magnet of magnetic moment M is placed in a uniform magnetic field B and rotated through an angle ฮธ from its equilibrium position. Derive the expression for the work done in this process.
Numerical & Application-Based Problems
Q16. A bar magnet of length 10 cm and pole strength 40 Am is placed in a uniform magnetic field of 0.5 T.
(a) Calculate its magnetic moment.
(b) Find the maximum torque experienced by the magnet.
(c) Calculate the work done in rotating the magnet from its stable equilibrium position to an unstable equilibrium position.
Q17. A circular coil of 100 turns, radius 5 cm, carries a current of 2 A.
(a) Calculate its magnetic dipole moment.
(b) The coil is placed in a uniform magnetic field of 0.4 T such that its plane makes an angle of 30ยฐ with the field. Calculate the torque on the coil.
(c) Through what minimum angle must the coil be rotated from this position for the torque to become zero?
Q18. In your school's physics laboratory, you have two bar magnets. Magnet A has length 8 cm and pole strength 30 Am. Magnet B has length 12 cm and pole strength 20 Am. Both are made of the same material.
(a) Calculate the magnetic moment of each magnet.
(b) If both magnets are placed in the same uniform magnetic field of 0.3 T, which magnet will experience greater maximum torque? By how much?
(c) A student suggests joining the two magnets end-to-end with opposite poles together to form a single magnet. Calculate the magnetic moment of the combined system and discuss whether this arrangement is practically useful.