CBSE Class 12th Physics Magnetism and Matter 100 MCQs

Physics – Magnetism and Matter

Class 12 Physics (Chapter 5) • 100 Multiple Choice Questions

Read Chapter Notes

Question 1

What is the SI unit of magnetic pole strength?

Correct Answer: Am

Question 2

The SI unit of magnetic dipole moment is:

Correct Answer: A m²

Question 3

Outside a bar magnet, the magnetic field lines travel from:

Correct Answer: North pole to South pole

Question 4

Inside a bar magnet, the magnetic field lines travel from:

Correct Answer: South pole to North pole

Question 5

Unlike electrostatic field lines, magnetic field lines:

Correct Answer: Form continuous closed loops

Question 6

Gauss's law for magnetism states that the net magnetic flux through any closed surface is:

Correct Answer: Zero

Question 7

The fact that the net magnetic flux through a closed surface is zero indicates that:

Correct Answer: Magnetic monopoles do not exist

Question 8

Torque (τ) acting on a magnetic dipole of moment m placed in a uniform magnetic field B is given by:

Correct Answer: τ = m × B

Question 9

The potential energy (U) of a magnetic dipole in a uniform magnetic field B is:

Correct Answer: U = -m · B

Question 10

A magnetic dipole is in stable equilibrium in a uniform magnetic field when the angle between m and B is:

Correct Answer: 0°

Question 11

A magnetic dipole is in unstable equilibrium in a uniform magnetic field when the angle between m and B is:

Correct Answer: 180°

Question 12

The torque is maximum on a magnetic dipole in a magnetic field when the angle is:

Correct Answer: 90°

Question 13

What is the work done in rotating a magnetic dipole from stable equilibrium to unstable equilibrium?

Correct Answer: 2mB

Question 14

Earth's magnetic field at the equator is approximately:

Correct Answer: 10⁻⁵ T

Question 15

The angle between the geographical meridian and the magnetic meridian is called:

Correct Answer: Magnetic declination

Question 16

The angle made by Earth's total magnetic field with the horizontal direction is called:

Correct Answer: Angle of dip (Inclination)

Question 17

What is the angle of dip at the magnetic equator?

Correct Answer: 0°

Question 18

What is the angle of dip at the magnetic poles?

Correct Answer: 90°

Question 19

If B is Earth's total magnetic field and I is the angle of dip, the horizontal component H is:

Correct Answer: B cos(I)

Question 20

If H is horizontal component and Z is vertical component of Earth's magnetic field, then tan(I) equals:

Correct Answer: Z / H

Question 21

A magnetic compass needle at Earth's magnetic north pole will:

Correct Answer: Rest in any direction horizontally (H=0, it cannot point to a specific horizontal direction)

Question 22

Which of the following is not an element of Earth's magnetic field?

Correct Answer: Magnetic susceptibility

Question 23

A dip circle at the magnetic equator shows a dip angle of:

Correct Answer: 0°

Question 24

The intensity of magnetization (M) is defined as:

Correct Answer: Magnetic dipole moment per unit volume

Question 25

What is the SI unit of Intensity of Magnetization (M)?

Correct Answer: A m⁻¹

Question 26

The relation between magnetic induction (B), magnetic intensity (H), and magnetization (M) is:

Correct Answer: B = μ₀(H + M)

Question 27

Magnetic susceptibility (χ) is defined as the ratio of:

Correct Answer: M to H

Question 28

The unit of magnetic susceptibility (χ) is:

Correct Answer: Dimensionless (No unit)

Question 29

Relative magnetic permeability (μ_r) is related to magnetic susceptibility (χ) by:

Correct Answer: μ_r = 1 + χ

Question 30

For diamagnetic materials, magnetic susceptibility (χ) is:

Correct Answer: Small and negative

Question 31

For paramagnetic materials, magnetic susceptibility (χ) is:

Correct Answer: Small and positive

Question 32

For ferromagnetic materials, magnetic susceptibility (χ) is:

Correct Answer: Large and positive

Question 33

Which of the following is a diamagnetic material?

Correct Answer: Copper (or Bismuth)

Question 34

Which of the following is a paramagnetic material?

Correct Answer: Aluminum

Question 35

Which of the following is a ferromagnetic material?

Correct Answer: Iron

Question 36

When a diamagnetic substance is brought near a strong magnet, it is:

Correct Answer: Weakly repelled

Question 37

In a non-uniform magnetic field, diamagnetic materials tend to move from:

Correct Answer: Stronger to weaker part

Question 38

In a non-uniform magnetic field, paramagnetic materials tend to move from:

Correct Answer: Weaker to stronger part

Question 39

Curie's Law states that magnetic susceptibility (χ) of a paramagnetic material is:

Correct Answer: Inversely proportional to T

Question 40

What happens to a ferromagnetic material when heated above its Curie temperature?

Correct Answer: It becomes paramagnetic

Question 41

Magnetic domain concept is applicable only to:

Correct Answer: Ferromagnetic materials

Question 42

In a hysteresis loop, the value of B when H is reduced to zero is called:

Correct Answer: Retentivity (or Remanence)

Question 43

In a hysteresis loop, the reverse magnetic field (H) required to reduce B to zero is called:

Correct Answer: Coercivity

Question 44

The area of the B-H hysteresis loop represents:

Correct Answer: Energy dissipated per unit volume per cycle

Question 45

A material suitable for making permanent magnets should have:

Correct Answer: High retentivity and high coercivity

Question 46

A material suitable for making electromagnets or transformer cores should have:

Correct Answer: High retentivity and low coercivity

Question 47

Soft iron is preferred for making electromagnets because it has:

Correct Answer: High permeability and low coercivity

Question 48

Which of the following is commonly used for making permanent magnets?

Correct Answer: Steel (or Alnico)

Question 49

If a magnet is broken into two halves along its axis, the pole strength of each new magnet will be:

Correct Answer: Half of original

Question 50

If a magnet is broken into two halves perpendicular to its axis, its magnetic moment M becomes:

Correct Answer: M / 2

Question 51

At the magnetic poles of Earth, a compass needle will:

Correct Answer: Be completely vertical (dip 90°)

Question 52

Magnetic lines of force of a bar magnet do not intersect because:

Correct Answer: Magnetic field has a unique direction at any point

Question 53

Susceptibility of a diamagnetic substance is:

Correct Answer: Negative and small

Question 54

According to Curie-Weiss law, susceptibility above Curie temp is proportional to:

Correct Answer: 1 / (T - T_c)

Question 55

What is the value of horizontal component of Earth's field at the magnetic poles?

Correct Answer: Zero

Question 56

Permeability of a diamagnetic substance is:

Correct Answer: Slightly less than 1

Question 57

Superconductors exhibit perfect diamagnetism. This effect is called:

Correct Answer: Meissner effect

Question 58

Magnetic lines of force are:

Correct Answer: Continuous closed curves

Question 59

A freely suspended magnetic needle will come to rest in the:

Correct Answer: Magnetic North-South direction

Question 60

In which material is the magnetic susceptibility temperature-independent?

Correct Answer: Diamagnetic

Question 61

Magnetic dipole moment is a:

Correct Answer: Vector quantity directed South to North

Question 62

The equivalent magnetic dipole moment of a current carrying coil (N turns, area A, current I) is:

Correct Answer: NIA

Question 63

Two identical magnetic dipoles each of moment M are placed at 90° to each other. Their resultant is:

Correct Answer: M√2

Question 64

A bar magnet is cut into two equal halves by a plane parallel to the magnetic axis. Its dipole moment becomes:

Correct Answer: M/2

Question 65

The direction of magnetic field on the equatorial line of a bar magnet is:

Correct Answer: Antiparallel to magnetic moment

Question 66

Magnetic field intensity on the axial line of a short bar magnet at distance d is proportional to:

Correct Answer: 1/d³

Question 67

What is the relation between axial (Ba) and equatorial (Be) magnetic fields of a short magnet at the same distance?

Correct Answer: Ba = 2 Be

Question 68

Which of the following is true for magnetic monopoles?

Correct Answer: They have never been observed to exist freely

Question 69

Liquid oxygen remains suspended between the poles of a strong magnet because it is:

Correct Answer: Paramagnetic

Question 70

Which of the following is diamagnetic?

Correct Answer: Water

Question 71

A bar magnet of moment M is bent into a semicircle. Its new magnetic moment will be:

Correct Answer: 2M/π

Question 72

What is the magnetic field at the center of a bar magnet?

Correct Answer: Maximum (Field lines are dense at the center internally)

Question 73

Relative permeability of a paramagnetic material is:

Correct Answer: μ_r > 1

Question 74

Relative permeability of a ferromagnetic material is:

Correct Answer: μ_r >> 1 (very large)

Question 75

Magnetic lines of force:

Correct Answer: Are imaginary curves to map magnetic field

Question 76

The hysteresis loop of soft iron is:

Correct Answer: Narrow

Question 77

The hysteresis loop of steel is:

Correct Answer: Broad

Question 78

Hysteresis loss is given by:

Correct Answer: Area of B-H loop

Question 79

Transformers have cores made of soft iron to minimize:

Correct Answer: Hysteresis loss

Question 80

A magnetic needle is kept in a non-uniform magnetic field. It experiences:

Correct Answer: A force and a torque

Question 81

Earth behaves as a magnet with magnetic poles near the geographic:

Correct Answer: North and South poles

Question 82

At neutral points, the resultant magnetic field is:

Correct Answer: Zero

Question 83

When a bar magnet is placed with its North pole pointing geographic North, neutral points are found on its:

Correct Answer: Equatorial line

Question 84

When a bar magnet is placed with its North pole pointing geographic South, neutral points are found on its:

Correct Answer: Axial line

Question 85

The temperature above which a ferromagnetic material becomes paramagnetic is:

Correct Answer: Curie temperature

Question 86

For a diamagnetic substance, relative permeability μ_r is:

Correct Answer: 0 < μ_r < 1

Question 87

A permanent magnet attracts:

Correct Answer: Ferromagnetic and paramagnetic, repels diamagnetic

Question 88

Electromagnets are made of soft iron because soft iron has:

Correct Answer: High retentivity and low coercivity (along with high permeability)

Question 89

The value of magnetic susceptibility for vacuum is:

Correct Answer: Zero

Question 90

Which property of a magnetic material makes it unsuitable for a transformer core?

Correct Answer: Broad hysteresis loop

Question 91

Magnetic field inside a tightly wound solenoid with current is due to:

Correct Answer: Moving charges (current)

Question 92

Curie temperature of iron is approximately:

Correct Answer: 1043 K (770°C)

Question 93

A magnetic dipole moment can be created by:

Correct Answer: A current carrying loop

Question 94

If a bar magnet is placed in a uniform magnetic field, the net force on it is:

Correct Answer: Zero

Question 95

Work done to rotate a magnet of dipole moment m by 180° from a direction parallel to magnetic field B is:

Correct Answer: 2mB

Question 96

Earth's magnetic field acts as if there is a huge bar magnet placed at:

Correct Answer: The geographic center

Question 97

A magnetic needle oscillates in a magnetic field. Its time period is given by T = 2π√(I / mB). What does 'I' represent?

Correct Answer: Moment of inertia

Question 98

The unit of magnetic flux is:

Correct Answer: Weber

Question 99

Alnico is an alloy commonly used to make:

Correct Answer: Permanent magnets

Question 100

If a magnetic dipole is placed in a non-uniform magnetic field, it experiences:

Correct Answer: Both force and torque