HC Verma solutions for Concepts of Physics Vol. 2 [English] Class 11 and 12 chapter 15 - Magnetic Properties of Matter [Latest edition]

When a dielectric is placed in an electric field, it gets polarised. The electric field in a polarised material is less than the applied field. When a paramagnetic substance is kept in a magnetic field, the field in the substance is more than the applied field. Explain the reason of this opposite behaviour.

The property of diamagnetism is said to be present in all materials. Then, why are some materials paramagnetic or ferromagnetic?

Do permeability and relative permeability have the same dimensions?

A rod, when suspended in a magnetic field, stays in the east-west direction. Can we be sure that the field is in the east-west direction? Can it be in the north-south direction?

Why is it not possible to make permanent magnets from paramagnetic materials?

Can we have magnetic hysteresis in paramagnetic or diamagnetic substances?

When a ferromagnetic material goes through a hysteresis loop, its thermal energy is increased. Where does this energy come from?

What are the advantages of using soft iron as a core, instead of steel, in the coils of galvanometers?

To keep valuable instruments away from the earth's magnetic field, they are enclosed in iron boxes. Explain.

A paramagnetic material is placed in a magnetic field. Consider the following statements:-
(A) If the magnetic field is increased, the magnetisation is increased.
(B) If the temperature is increased, the magnetisation is increased.

A paramagnetic material is kept in a magnetic field. The field is increased till the magnetisation becomes constant. If the temperature is now decreased, the magnetisation ___________ .

A ferromagnetic material is placed in an external magnetic field. The magnetic domains ______________ .

A long, straight wire carries a current i. The magnetising field intensity H is measured at a point P close to the wire. A long, cylindrical iron rod is brought close to the wire, so that the point P is at the centre of the rod. The value of H at P will ______________ .

The magnetic susceptibility is negative for _____________ .

The desirable properties for making permanent magnets are _________________ .

Electromagnets are made of soft iron because soft iron has _______________ .

Pick the correct options.
(a) All electrons have magnetic moment.
(b) All protons have magnetic moment.
(c) All nuclei have magnetic moment.
(d) All atoms have magnetic moment.

The permanent magnetic moment of the atoms of a material is not zero. The material ________________ .

The permanent magnetic moment of the atoms of a material is zero. The material _________________ .

Which of the following pairs has quantities of the same dimensions?
(a) Magnetic field B and magnetising field intensity H
(b) Magnetic field B and intensity of magnetisation I
(c) Magnetising field intensity H and intensity of magnetisation I
(d) Longitudinal strain and magnetic susceptibility

When a ferromagnetic material goes through a hysteresis loop, the magnetic susceptibility
(a) has a fixed value
(b) may be zero
(c) may be infinity
(d) may be negative

Mark out the correct options.
(a) Diamagnetism occurs in all materials.
(b) Diamagnetism results from the partial alignment of permanent magnetic moment.
(c) The magnetising field intensity, H, is always zero in free space.
(d) The magnetic field of induced magnetic moment is opposite the applied field.

The magnetic intensity H at the centre of a long solenoid carrying a current of 2.0 A, is found to be 1500 A m⁻¹. Find the number of turns per centimetre of the solenoid.

A rod is inserted as the core in the current-carrying solenoid of the previous problem. (a) What is the magnetic intensity H at the centre? (b) If the magnetization I of the core is found to be 0.12 A m⁻¹, find the susceptibility of the material of the rod. (c) Is the material paramagnetic, diamagnetic or ferromagnetic?

The magnetic field inside a long solenoid of 50 turns cm⁻¹ is increased from 2.5 × 10⁻³ T to 2.5 T when an iron core of cross-sectional area 4 cm² is inserted into it. Find (a) the current in the solenoid (b) the magnetisation I of the core and (c) the pole strength developed in the core.

A bar magnet of length 1 cm and cross-sectional area 1.0 cm² produces a magnetic field of 1.5 × 10⁻⁴ T at a point in end-on position at a distance 15 cm away from the centre. (a) Find the magnetic moment M of the magnet. (b) Find the magnetisation I of the magnet. (c) Find the magnetic field B at the centre of the magnet.

The susceptibility of annealed iron at saturation is 5500. Find the permeability of annealed iron at saturation.

The magnetic field B and the magnetic intensity H in a material are found to be 1.6 T and 1000 A m⁻¹, respectively. Calculate the relative permeability µ_r and the susceptibility χ of the material.

The susceptibility of magnesium at 300 K is 1.2 × 10⁻⁵. At what temperature will the susceptibility increase to 1.8 × 10⁻⁵?

Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magnetons (1 Bohr magneton equals 9.27 × 10⁻²⁴ A m²). The density of atoms in iron is 8.52 × 10²⁸ atoms m⁻³. (a) Find the maximum magnetisation I in a long cylinder of iron (b) Find the maximum magnetic field B on the axis inside the cylinder.

The coercive force for a certain permanent magnet is 4.0 × 10⁴ A m⁻¹. This magnet is placed inside a long solenoid of 40 turns/cm and a current is passed in the solenoid to demagnetise it completely. Find the current.