# Physics MCQs for Class 12 with Answers Chapter 5 Magnetism and Matter

Free PDF Download of CBSE Physics Multiple Choice Questions for Class 12 with Answers Chapter 5 Magnetism and Matter. Physics MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Physics Magnetism and Matter MCQs Pdf with Answers to know their preparation level.

## Magnetism and Matter Class 12 Physics MCQs Pdf

MCQ on Magnetism Class 12 Question 1. A toroid of n turns, mean radius R and crosssectional radius a carries current I. It is placed on a horizontal table taken as x-y plane. Its magnetic moment m [NCERT Exemplar]
(a) is non-zero and points in the z-direction by symmetry.
(b) points along the axis of the tortoid (m = mΦ).
(c) is zero, otherwise there would be a field falling as $$\frac{1}{r^{3}}$$ at large distances outside r3 the toroid.

Explaination:
(c) For any point inside the empty space surrounded by toroid and outside the toroid, the magnetic field B is zero because the net current enclosed in these spaces is zero.

MCQ Physics Class 12 Question 2. The magnetic field of Earth can be modelled by that of a point dipole placed at the centre of the Earth. The dipole axis makes an angle of 11.3° with the axis of Earth. At Mumbai, ‘declination is nearly zero. Then, [NCERT Exemplar]
(a) the declination varies between 11.3° W to 11.3° E.
(b) the least declination is 0°.
(c) the plane defined by dipole axis and Earth axis passes through Greenwich.
(d) declination averaged over Earth must be always negative.

Explaination:
(a) The axis of the dipole does not coincide with the axis of rotation of the earth and it is tilted at some angle.

3. In a permanent magnet at room temperature [NCERT Exemplar]
(a) magnetic moment of each molecule is zero.
(b) the individual molecules have non-zero magnetic moment which are all perfectly aligned.
(c) domains are partially aligned.
(d) domains are all perfectly aligned.

CBSE Class 12 Physics MCQs with Answer: c
Explaination:
(c) At room temperature, the permanent magnet retains ferromagnetic property for a long period of time.

Physics MCQs For Class 12 with Answers Chapter wise Pdf Question 4. Consider the two idealized systems:
(i) a parallel plate capacitor with large plates and small separation and (ii) a long solenoid of length L » R, radius of cross-section. In (i) E is ideally treated as a constant between plates and zero outside. In (ii) magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below: [NCERT Exemplar]
(a) case (i) contradicts Gauss’s law for electrostatic fields.
(b) case (ii) contradicts Gauss’s law for magnetic fields.
(c) case (i) agrees with ∫ E.dl = 0 .
(d) case (ii) contradicts ∫ H.dl = Ien

Explaination:
(b) The electrostatic field lines do not form a continuous closed path, while the magnetic field lines form the closed paths.

5. A paramagnetic sample shows a net magnetisation of 8 Am-1 when placed in an external magnetic field of 0.6 T at a temperature of 4K. When the same sample is placed in an external magnetic field of 0.2 T at a temperature of 16 K, the magnetisation will be [NCERT Exemplar]
(a) $$\frac{32}{3}$$ Am-1
(b) $$\frac{2}{3}$$ Am-1
(c) 6 Am-1
(d) 2.4 Am-1

6. S is the surface of a lump of magnetic material.
(a) Lines of B are not necessarily continuous across S.
(b) Some lines of B must be discontinuous across S.
(c) Lines of H are necessarily continuous across S.
(d) Lines of H cannot all be continuous across S.

7. The primary origin(s) of magnetism lies in
(a) Pauli exclusion principle.
(b) polar nature of molecules.
(c) intrinsic spin of electron.
(d) None of these.

Explaination:
(b) The primary origin of magnetism lies in the fact that the electrons are revolving and spinning about the nucleus of an atom.

8. A long solenoid has 1000 turns per metre and carries a current of 1 A. It has a soft iron core of μr = 1000. The core is heated beyond the Curie temperature, Tc .
(a) The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
(b) The H and B fields in the solenoid are nearly unchanged.
(c) The magnetisation in the core reverses direction.
(d) The magnetisation in the core does not diminishes.

Explaination:
(a) At normal temperature, a solenoid behaves as a ferromagnetic substance and at the temperature beyond the Curie temperature, it behaves as a paramagnetic substance.

9. Essential difference between electrostatic shielding by a conducting shell and magne-tostatic shielding is due to
(a) electrostatic field lines cannot end on ’ charges and conductors do not have free charges.
(b) lines of B can also end but conductors cannot end them.
(c) lines of B cannot end. on any material and perfect shielding is not possible.
(d) shells of high permeability materials cannot be used to divert lines of B from the interior region.

Explaination:
(c) As magnetostatic shielding is done by using an enclosure made of a high permeability magnetic material to prevent a static magnetic field outside the enclosure from reaching objects inside it or to confine a magnetic field within the enclosure

10. Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator
(a) is always zero.
(b) can be zero at specific points.
(c) cannot be positive or negative.
(d) is not bounded.

Explaination:
(b) As the angle of dip at a point on the geographical equator is bounded in a range from positive to negative value.

11. A magnetic needle is kept in a non-uniform magnetic field. It experiences
(a) a torque but not a force.
(b) neither a force nor a torque.
(c) a force and a torque.
(d) a force but not a torque.

Explaination:
(c) As magnetic needle experiences both torque and force in a non-uniform magnetic field, because unequal and non-linear forces are exerted on its poles.

MCQ on Magnetism Class 12 Pdf Question 12. A 25 cm long solenoid has radius 2 cm and 500 total number of turns. It carries a current of 15 A. If it is equivalent to a magnet of the same size and magnetisation $$\overline{\mathbf{M}}$$, then |$$\overline{\mathbf{M}}$$| is
(a) 3 π Am-1
(b) 30000 π Am-1
(c) 300 Am-1
(d) 30000 Am-1

Explaination: 13. Three needles N1 N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet, when brought close to them, will
(а) attract N1 strongly, but repel N2 and N3 weakly.
(b) attract all three of them.
(c) attract N1 and N2 strongly but repel N3.
(d) attract N1 strongly, N2 weakly and repel N3 weakly.

14. Curie temperature is the temperature above which
(a) a ferromagnetic material becomes paramagnetic.
(b) a ferromagnetic material becomes diamagnetic.
(c) a paramagnetic material becomes diamagnetic.
(d) a paramagnetic material becomes ferromagnetic.

Explaination:
(a) A ferromagnetic material becomes paramagnetic above the curie temperature.

15. The material suitable for making electromagnets should have
(a) high retentivity and high coercivity.
(b) low retentivity and low coercivity.
(c) high retentivity and low coercivity.
(d) low retentivity and high coercivity.

16. Curie law xT = constant, relating magnetic susceptibility (x) and absolute temperature (T) of magnetic substance is obeyed by
(a) all magnetic substances.
(b) paramagnetic substances.
(c) diamagnetic substances.
(d) ferromagnetic substances.

17. If Mis magnetic moment and B is magnetic field intensity, then the torque is given by Explaination:
(c) Torque, $$\bar{\tau}=\overline{\mathbf{M}} \times \overline{\mathbf{B}}$$

18. Angle of dip is 90° at
(a) poles.
(b) equator.
(c) both at equator and poles.
(d) tropic of cancer.

19. Lines of force, due to earth’s horizontal magnetic field, are
(a) elliptical
(b) curved lines
(c) concentric circles
(d) parallel and straight

20. If the magnetising field on a ferromagnetic material is increased, its permeability.
(a) is decreased
(b) is increased
(c) is unaffected
(d) may be increased or decreased.

Explaination:

(a), Since, $$\mu=\frac{\mathrm{B}}{\mathrm{H}} \Rightarrow \mu \propto \frac{1}{\mathrm{H}}$$

21. A magnetic needle suspended parallel to a magnetic field requires /3 J of work to turn it through 60°. The torque needed to maintain the needle in this position will be Explaination: 22. The magnetic susceptibility of an ideal diamagnetic substance is
(a) +1
(b) 0
(c) -1
(d) ∞

Explaination: (c) Since, for diamagnetic -1 ≤ xm < 0

23. The best material for the ore of a transformer is
(a) stainless steel
(b) mild steel
(c) hard steel
(d) soft iron

Explaination: (d) Since, soft iron has high permeability and low retentivity.

24. Domain formation is the necessary feature of
(a) diamagnetism.
(h) Paramagnetis.
(c) ferromagnetism.
(d) all of these.

Explaination: (c) Ferromagnetism is explained on the basis of domain formation.

Physics Class 12 MCQs Pdf Question 25. The variation of magnetic susceptibility with the temperature of a ferromagnetic material can be plotted as Explaination:
(b) Since susceptibility (xm) of ferromagneticmaterial decreases with increase in temperature and above curie temperature Tc, it becomes paramagnetic.

26. In which type of material the magnetic susceptibility does not depend on temperature?
(a) Diamagnetic
(b) Paramagnetic
(c) Ferromagnetic
(d) Ferrite

27. A diamagnetic material in a magnetic field moves
(a) perpendicular to the field.
(b) from weaker to stronger parts.
(c) from stronger to weaker parts.
(d) in random direction.

Explaination:
(c) A diamagnetic material is repelled by magnetic field so it moves slowly from stronger to weaker part.

28. At a certain place on earth, $$B_{H}=\frac{1}{\sqrt{3}} B_{V}$$ angle of dip at this place is
(a) 60°
(b) 30°
(c) 45°
(d) 90°

Explaination: 29. The universal property among all substances is
(a) diamagnetism.
(b) paramagnetism.
(c) ferromagnetism.
(d) all of these.

Explaination: (a) Diamagnetism is the universal property of all substances.

30. At a point on the right bisector of a magnetic dipole, the magnetic
(a) potential varies as $$\frac{1}{r²}$$
(b) potential is zero at all points on the right bisector.
(c) field varies as r3.
(d) field is perpendicular to the axis of dipole.

Explaination:
(b) At any point on the right bisector the potential due to the two poles are equal and opposite.

31. A magnet of dipole moment M is aligned in equilibrium position in a magnetic field of intensity B. The work done to rotate it through an angle 0 with the magnetic field is
(a) MB sin θ
(b) MB cos θ
(c) MB (1 – cos θ)
(d) MB(l – sin θ)

Explaination:
(c) , At equilibrium position θ = 0,
Work done, W = $$\int_{0}^{\theta}$$ MB sin θ d θ
= MB( 1 – sin θ)

32. A magnet can be completely demagnetised by
(a) breaking the magnet into small pieces.
(b) heating it slightly.
(c) dropping it into ice cold water.
(d) a reverse field of appropriate strength.

33. The primary origin of magnetism lies in
(a) atomic current and intrinsic spin of electrons.
(b) polar and non polar nature of molecules.
(c) pauli exclusion principle.
(d) electronegative nature of materials.

34. Magnetic moment for solenoid and corresponding bar magnet is
(a) equal for both
(b) more for solenoid
(c) more for bar magnet
(d) none of these

35. Which of the following is correct about magnetic monopole?
(a) Magnetic monopole exist.
(b) Magnetic monopole does not exist.
(c) Magnetic monopole have constant value of monopole momentum.
(d) The monopole momentum increase due to increase at its distance from the field.

36. Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure. The force on the charge Q is (a) zero
(b) directed along OP
(c) directed along PO
(d) directed perpendicular to the plane of paper

37. A current carrying loop is placed in a uniform magnetic field in four different orientations as shown in figure. Arrange them in the decreasing order of potential energy. (a) 4, 2, 3,1
(b) 1, 4, 2, 3
(c) 4, 3, 2,1
(d) 1, 2, 3, 4

38. Which of the following is not showing the essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding?
(a) Electrostatic field lines can end on charges and conductors have free charges.
(b) Magnetic field lines can end but conductors cannot end them.
(c) Lines of magentic field cannot end on any material and perfect shielding is not possible.
(d) Shells of high permeability materials can be used to divert lines of magnetic field from the interior region.

39. The net magnetic flux through any closed surface, kept in a magnetic field is
(a) zero
(b) $$\frac{\mu_{0}}{4 \pi}$$
(c) 4πμ0
(d) $$\frac{4 \mu_{0}}{\pi}$$

40. Point out the correct direction of magnetic field in the given figures. 41. The earth behaves as a magnet with magnetic field pointing approximately from the geographic
(a) North to South
(b) South to North
(c) East to West
(d) West to East

42. The strength of the earth’s magnetic field is
(a) constant everywhere.
(b) zero everywhere.
(c) having very high value.
(d) vary from place to place on the earths surface.

43. Which of the following is responsible for the earth’s magnetic field?
(а) Convective currents in earth’s core
(б) Diversive current in earth’s core.
(c) Rotational motion of earth.
(d) Translational motion of earth.

44. Which of the following independent quantities is not used to specify the earth’s magnetic field?
(a) Magnetic declination (θ).
(b) Magnetic dip (δ).
(c) Horizontal component of earth’s field (BH).
(d) Vertical component of earth’s field (BV).

45. Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator is
(a) always zero
(b) positive, negative or zero
(c) unbounded
(d) always negative

46. The angle of dip at a certain place where the horizontal and vertical components of the earth’s magnetic field are equal is
(a) 30°
(b) 75°
(c) 60°
(d) 45°

47. The vertical component of earth’s magnetic field . at a place is √3 times the horizontal component
the value of angle of dip at this place is
(a) 30°
(b) 45°
(c) 60°
(d) 90°

48. At a given place on earth’s surface the horizontal component of earth’s magnetic field is 2 × 103-5 T and resultant magnetic field is 4 × 103-5 T. The angle of dip at this place is
(a) 30°
(b) 60°
(c) 90°
(d) 45°

49. Which of the following property shows the property of ferromagnetic substances?
(a) The ferromagnetic property depends on tem-perature. ‘
(b) The ferromagnetic property does not depend on temperature.
(c) At high enough temperature ferromagnet becomes a diamagnet.
(d) At low temperature ferromagnet becomes a paramagnet.

50. Gauss’s law in magnetism indicates that magnetic ________ do not exist.

Explaination: monopoles.

51. Magnetic dipole moment associated with an electron due to its orbital motion in first orbit of H-atom is known as ________ .

Explaination: Bohr magneton.

52. Magnetic lines of force form closed loop. They converge at ________ pole and diverge at ________ pole.

Explaination: south, north

53. Angle between the geographical meridian and magnetic meridian at the given place is known as ________ .

Explaination: magnetic declination (∝)

54. Angle made by the earth’s total magnetic field with the horizontal direction is known as ________ .

Explaination: angle of dipole (δ)

55. S.I. unit of magnetic dipole moment is ________ .

Explaination: Am²

56. Magnetic moment developed per unit volume of a material when placed in a magnetising field is known as ________ .

Explaination: intensity of magnetisation.

57. Which orientation of a magnetic dipole in a uniform magnetic field will correspond to its stable equilibrium? [HOTS]

Explaination:
In stable equilibrium, the dipole moment vector and the magnetic field vector are in same direction.

58. Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero?

Explaination:
Yes. The average of the charge in the system may be zero. Yet, the mean of the magnetic moments due to various current loops may not be zero. In paramagnetic material, the atoms have net dipole moment though their net charge is zero.

59. If magnetic monopoles existed, how would the Gauss’s law of magnetism be modified? [Delhi 2019]

Explaination:
Gauss’s law of magnetism states that the flux of B through any closed surface is always zero $$\oint_{s}$$B .ds = 0. If the monopole existed, then Gauss’s law would have been $$\oint \vec{B} \cdot \overrightarrow{d s}$$ = μ0qm where qm is magnetic charge (monopole) enclosed by the surface.

60. Must every magnetic configuration have a north pole and a south pole? What about the field due to a toroid?

Explaination:
Not necessarily. True only if the source of the field has a net non-zero magnetic moment. This is not so for a toroid or even for a straight infinite conductor.

61. Does a bar magnet exert a toque on itself due to its own field? Does on element of a current-carrying wire exert a force on another element of the same wire?

Explaination:
No. There is no force or torque on a element due to the field produced by that element itself. But there is a force (or torque) on an element of the same wire.

62. A magnetised needle 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 a torque. Why?

Explaination:
No force, if the field is uniform. The iron nail experiences a non-uniform field due to the bar magnet. There is induced magnetic moment in the nail, therefore, it experiences both force and torque. The net force is attractive because the induced south pole (say) in the nail is closer to the north pole of magnet than induced north pole.

63. 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 its length? [HOTS]

Explaination:
(i) The pole strength does not change.
(ii) The magnetic moment reduces to half.

64. What happens if a bar magnet is cut into two pieces: (i) transverse to its length, (ii) along its length?

Explaination:
In either case, one gets two magnets, each with a north and south pole.

65. 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 along its length? [HOTS]

Explaination:
(i) The pole strength becomes half.
(ii) The magnetic magnet becomes half.

66. 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?

Explaination:
No. The magntic force is always normal to B (remember magnetic force = q($$\vec{v} \times \vec{B}$$). Therefore it is misleading to call magnetic field lines as lines of force.

67. Magnetic field lines can be entirely confined ’within the core of a toroid, but not within a straight solenoid. Why?

Explaination:
According to the Gauss’s law, $$\oint \vec{B} \cdot \overrightarrow{d s}$$ =0, which is true for a as has no ends. But, in case of a solenoid, at each end the magnetic flux will not be zero, if the magnetic field lines were entirely confined within the solenoid.

68. What is the angle of dip at a place where the horizontal and vertical components of the earth’s magnetic field are equal? [Foreign 2012]

Explaination:
Angle of dip is 45°.

69. 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 which one? [Use nothing else but the bars A and B.]

Explaination:
Let, two bars are A and B. Now, bring one end of A near to B, and move it slowly (from one end to the middle).
If force experienced by bar A reduces as we move towards middle, then bar B is magnetised, and A is not.
If A experiences repulsion, then both the bars are magnetised.

70. A magnetic needle, free to rotate in a vertical plane, orients itself vertically at a certain place on the Earth. What are the values of (i) horizontal component of earth’s magnetic field, and (ii) angle of dip at this placed? [Foreign 2012]

Explaination: (i) Zero (ii) 90°

71. At a place, the horizontal component of earth’s magnetic field is B and angle of dip is 60°. What is the value of horizontal component of the earth’s magnetic field at equator? [Delhi 2017]

Explaination: 72. Which of the following substances are paramagnetic?
Bi, Al, Cu, Ca, Pb and Ni [Delhi 2013]

Explaination: Al and Ca.

73. Which of the following substances are diamagnetic?
Bi, Al, Na, Cu, Ca and Ni [Delhi 2013]

Explaination: Bi and Cu.

74. The susceptibility of a magnetic material is -4.2 × 10-6. Name the type of magnetic material it represents. [Chennai 2019] [Delhi 2011]

Explaination: Diamagnetic.

75. The susceptibility of a magnetic material is 0.9853. Identify the type of magnetic material. Draw the modification of the field pattern on keeping a piece of this material in a uniform magnetic field. [CBSE 2018]

Explaination: Paramagnetic

76. What are permanent magnets? Give one example. [Delhi 2013]