Magnetism and Matter quiz

Magnetic field lines:

The net magnetic flux through any closed surface is:

The SI unit of magnetic dipole moment is:

The susceptibility of a diamagnetic material is:

Above the Curie temperature, a ferromagnetic material becomes:

A superconductor is a perfect:

The torque on a magnetic dipole in a uniform field B is:

The magnetic moment of a solenoid of N turns, area A, carrying current I is:

The relative permeability of a diamagnetic material is:

Which of the following is paramagnetic?

Why is a bar magnet called a magnetic dipole? (2 marks)

Why are magnetic monopoles not found? (2 marks)

Why is soft iron used for electromagnets? (2 marks)

What happens when a diamagnetic substance is placed in a non-uniform magnetic field? (2 marks)

Write the relation between B, H and M. (2 marks)

Explain domain formation in ferromagnetic materials. (2 marks)

Why does a paramagnetic material become more strongly magnetised at low temperatures? (2 marks)

When is the potential energy of a magnetic dipole in a uniform field minimum? (2 marks)

Write the expression for the magnetic field on the equatorial line of a short bar magnet. (2 marks)

Why does a magnetic needle placed in a uniform field experience a torque but no net force? (2 marks)

A magnet of moment 2 A m^2 is placed at 60 degrees to a field of 0.5 T. Find the torque on it. (3 marks)

A solenoid of 500 turns and area 1 x 10^-3 m^2 carries 2 A. Find its magnetic moment. (3 marks)

Find the magnetic field on the equatorial line at 20 cm from the centre of a short magnet of moment 1.6 A m^2. (3 marks)

The susceptibility of a paramagnetic material is 1.2 x 10^-5 at 300 K. Find it at 150 K. (3 marks)

The susceptibility of bismuth is -1.66 x 10^-5. Find its relative permeability and permeability. (3 marks)

Read the passage and answer the questions. In a famous experiment, a live frog was levitated in a very strong magnetic field of about 16 T. Water and most organic materials in the frog are weakly repelled by the field. (i) What type of magnetic material is water? (ii) Why is the frog pushed away from the strong field region? (iii) Why is a very strong field needed? (5 marks)

Read the passage and answer the questions. A student places a compass needle at various points around a bar magnet and marks the direction of the needle to trace field lines. (i) Why does the compass align along field lines? (ii) Where are field lines most crowded? (iii) What happens to field lines inside the magnet? (5 marks)

Read the passage and answer the questions. In scrap yards, a large electromagnet with a soft iron core lifts heavy iron objects and releases them when the current is switched off. (i) Why is soft iron used as the core? (ii) Why would steel be unsuitable? (iii) What type of material is soft iron? (5 marks)

Read the passage and answer the questions. A student heats an iron nail attracted to a magnet using a flame. At a certain temperature, the nail falls off. On cooling, it is attracted again. (i) Why does the nail fall off? (ii) Name the temperature. (iii) What is the Curie temperature of iron approximately? (5 marks)

Read the passage and answer the questions. When some materials are cooled below a critical temperature, they expel magnetic field lines completely. A small magnet placed above them floats. (i) Name this effect. (ii) What is the susceptibility of such a material? (iii) Give one application. (5 marks)

Show that a current-carrying solenoid behaves like a bar magnet, and derive the expression for the magnetic field on the axis of a bar magnet. (6 marks)

Derive expressions for the torque and potential energy of a magnetic dipole in a uniform magnetic field. Discuss stable and unstable equilibrium. (6 marks)

Explain diamagnetism, paramagnetism and ferromagnetism on the basis of atomic magnetic moments and domains, with diagrams. (6 marks)

Define magnetic intensity, magnetisation, susceptibility and permeability, and derive the relation mu_r = 1 + chi. (6 marks)

State Gauss's law for magnetism and compare an electric dipole with a magnetic dipole, using field line diagrams. (6 marks)