Magnetism and Matter Premium Tutorials

Derivation of Magnetic Field due to bar magnets and solenoid

Magentic dipole ketp in presence of uniform magnetic field

Question Bank

Set – 1

I. Very Short Answer Type Questions (1 Mark)

  1. Can two magnetic field lines intersect? Justify your answer.
  2. Magnetic field lines always form a closed loop. Comment.
  3. What is the basic difference between electric and magnetic field lines?
  4. What is the SI unit of (i) pole strength and (ii) magnetic moment of a bar magnet?
  5. What is the name given to the curves the tangent to which at any point gives the directions of the magnetic field at that point? Can two such curves intersect each other? Justify your answer.
  6. Must every magnetic configuration have a north pole and a south pole? What about the field due to a toroid? [NCERT]
  7. Magnetic field lines show the direction (at every point) along which a small magnetised needle aligns (at the point). Do the magnetic field lines also represent the lines of force on a moving charged particle at every point? [NCERT]
  8. If magnetic monopoles existed, how would the Gauss’s law of magnetism be modified? [NCERT]
  9. Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero? [NCERT]
  10. How does the (i) pole strength and (ii) magnetic moment of each part of a bar magnet change if it is cut into two equal pieces transverse to length?
  11. A hypothetical bar magnet (AB) is cut into two equal parts. One part is now kept over the other, so that the pole C₂ is above C₁. If m is the magnetic moment of the original magnet, what would be the magnetic moment of the combination, so formed?
  12. What should be the orientation of a magnetic dipole in a uniform magnetic field so that its potential energy is maximum?

II. Short Answer Type Questions – I (2 Marks)

  1. Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why? [NCERT]
  2. A magnetic needle suspended freely in a uniform magnetic field experiences a torque but no net force. An iron nail near a bar magnet, however, experiences a force of attraction in addition to torque, why? [HOTS]
  3. A bar magnet of magnetic moment m is aligned parallel to the direction of a uniform magnetic field B. What is the work done, to turn the magnet so as to align its magnetic moment:
    (i) opposite to the field direction and
    (ii) normal to the field direction?
  4. Two identical looking iron bars A and B are given, one of which is definitely known to be magnetised. (We do not know which one). How would one ascertain whether or not both are magnetised? If only one is magnetised, how does one ascertain which one? [Use nothing else but the bars A and B]. [NCERT]
  5. A bar magnet is placed in a uniform magnetic field with its magnetic moment making an angle θ with the field.
    (i) Write an expression for the torque acting on the magnet and hence define its magnetic moment.
    (ii) Write an expression for the potential energy of the magnet in this orientation, when is this energy minimum.

Key for Set – 1

Set-2

Key for Set-2

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