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

Students of class 12 Physics should refer to MCQ Questions Class 12 Physics Magnetism and Matter with answers provided here which is an important chapter in Class 12 Physics NCERT textbook. These MCQ for Class 12 Physics with Answers have been prepared based on the latest CBSE and NCERT syllabus and examination guidelines for Class 12 Physics. The following MCQs can help you to practice and get better marks in the upcoming class 12 Physics examination

## Chapter 5 Magnetism and Matter MCQ with Answers Class 12 Physics

MCQ Questions Class 12 Physics Magnetism and Matter provided below have been prepared by expert teachers of grade 12. These objective questions with solutions are expected to come in the upcoming Standard 12 examinations. Learn the below provided MCQ questions to get better marks in examinations.

Question. A bar magnet of magnetic moment m is placed in a uniform magnetic field of induction B The torque exerted on it is

C

Question. Magnetism in substances is caused by
(a) orbital motion of electrons only
(b) spin motion of electrons only
(c) due to spin and orbital motions of electrons both
(d) hidden magnets

C

Question. Consider the two idealised 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
(a) case (i) contradicts Gauss’ law for electrostatic fields
(b) case (ii) contradicts Gauss’ law for magnetic fields
(c) case (i) agrees with ϕ E.dl = 0.
(d) case (ii) contradicts ϕ H.dl = Ien

B

Question. 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 4 K. 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

B

Question. A bar magnet of length ‘l’ and magnetic dipole moment ‘M’ is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be

A

Question. A uniform magnetic field exists in space in the plane of paper and is initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by

B

Question. In a plane perpendicular to the magnetic meridian, the dip needle will be
(a) vertical
(b) horizontal
(c) inclined equal to the angle of dip at that place
(d) pointing in any direction

A

Question. A permanent magnet attracts
(a) all substances
(b) only ferromagnetic substances
(c) some substances and repels others
(d) ferromagnetic substances and repels all others

B

Question. 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 4 K. 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
(a) (32/3) AM1
(b) (2/3) AM1
(c) 6 AM-1
(d) 24 AM-1

B

Question. A long solenoid has 1000 turns per metre and carries a current of 1 A. It has a soft iron core a of μr =1000. The core is heated beyond the Curie temperature, Tc , then
(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 diminishes by a factor of about 108.

A, D

Question. In a permanent magnet at room temperature
(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.

C

Question. The meniscus of a liquid contained in one of the limbs of a narrow U-tube is placed between the pole-pieces of an electromagnet with the meniscus in a line with the field. When the electromagnet is switched on, the liquid is seen to rise in the limb. This indicates that the liquid is
(a) ferromagnetic
(b) paramagnetic
(c) diamagnetic
(d) non-magnetic

B

Question. Susceptibility is positive for
(a) paramagnetic substances
(b) ferromagnetic substances
(c) non-magnetic substances
(d) diamagnetic substances

A, B

Question. Electro-magnets are made of soft iron because soft iron has
(a) small susceptibility and small retentivity
(b) large susceptibility and small retentivity
(c) large permeability and large retentivity
(d) small permeability and large retentivity.

B

Question. Points A and B are situated perpendicular to the axis of a 2 cm long bar magnet at large distances x and 3x from its centre on opposite sides. The ratio of the magnetic fields at A and B will be approximately equal to
(a) 1: 9
(b) 2: 9
(c) 27: 1
(d) 9: 1

C

Question. 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,
(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.

A

Question. If a magnetic substance is kept in a magnetic field, then which of the following substances is thrown out?
(a) Paramagnetic
(b) Ferromagnetic
(c) Diamegnetic
(d) Antiferromagnetic

C

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

C

Question. Above Curie’s temperature ferromagnetic substances becomes
(a) paramagnetic
(b) diamagnetic
(c) superconductor
(d) no change

A

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

A

Question. In the hysteresis cycle, the value of H needed to make the intensity of magnetisation zero is called
(a) retentivity
(b) coercive force
(c) Lorentz force
(d) none of the above

B

Question. If the horizontal and vertical components of earth’s magnetic field are equal at a certain place, the angle of dip is
(a) 90°
(b) 60°
(c) 45°
(d) 0°

C

Question. The main difference between electric lines of force and magnetic lines of force is
(a) electric lines of force are closed curves whereas magnetic lines of force are open curves
(b) electric lines of force are open curves whereas magnetic lines of force are closed curves
(c) magnetic lines of force cut each other whereas electric lines of force do not cut
(d) electric lines of force cut each other whereas magnetic lines of force do not cut

B

Question. The line on the earth surface joining the point where the field is horizontal, is called
(a) magnetic equator
(b) magnetic line
(c) magnetic axis
(d) magnetic inertia

A

Question. When a ferromagnetic material is heated to temperature above its Curie temperature, the material
(a) is permanently magnetized
(b) remains ferromagnetic
(c) behaves like a diamagnetic material
(d) behaves like a paramagnetic material

D

Question. The force between two short bar magnets with magnetic moments M1 and M2 whose centres are r metres apart is 8 N when their axes are in same line. if the separation is increased to 2 r, the force between them in reduced to
(a) 4 N
(b) 2 N
(c) 1 N
(d) 0.5 N

D

Question. A superconductor exhibits perfect :
(a) ferrimagnetism
(b) ferromagnetism
(c) paramagnetism
(d) diamagnetism

D

Question. In end on and broadside on position of a deflection magnetometer, if θ1 and θ2 are the deflections produced by short magnets at equal distances, then tanθ1/ tanθ2 is
(a) 2 : 1
(b) 1 : 2
(c) 1 : 1
(d) None of these

A

Question. A watch glass containing some powdered substance is placed between the pole pieces of a magnet. Deep concavity is observed at the centre. The substance in the watch glass is
(a) iron
(b) chromium
(c) carbon
(d) wood

A

Question. 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
(a) attract N1 and N2 strongly but repel N3
(b) attract N1 strongly, N2 weakly and repel N3 weakly
(c) attract N1 strongly, but repel N2 and N3 weakly
(d) attract all three of them

B

Question. If horizontal and vertical components of earths magnetic field are equal, then angle of dip is
(a) 60°
(b) 45°
(c) 30°
(d) 90°

B

Question. For protecting a sensitive equipment from the external electric arc, it should be
(a) wrapped with insulation around it when passing current through it
(b) placed inside an iron can
(c) surrounded with fine copper sheet
(d) placed inside an aluminium can

B

Question. If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by μd, μp and μf respectively, then
(a) μd = 0 and μp ≠ 0
(b) μd ≠ 0 and μp = 0
(c) μp = 0 and μf ≠ 0
(d) μd ≠ 0 and μf ≠ 0

A

Question. A dip circle is so set that its needle moves freely in the magnetic meridian. In this position, the angle of dip is 40º. Now the dip circle is rotated so that the plane in which the needle moves makes an angle of 30º with the magnetic meridian. In this position, the needle will dip by an angle
(a) 40º
(b) 30º
(c) more than 40º
(d) less than 40º

D

Question. Current i is flowing in a coil of area A and number of turns N, then magnetic moment of the coil, M is
(a) NiA
(a) Ni/A
(a) Ni/√A
(a) N2Ai

A

Question. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show
(a) anti ferromagnetism
(b) no magnetic property
(c) diamagnetism
(d) paramagnetism

D

Question. A thin rectangular magnet suspended freely has a period of oscillation of 4 s. If it is broken into two halves (each having half the original length) and one of the pieces is suspended similarly. The period of its oscillation will be
(a) 4 s
(b) 2 s
(c) 0.5 s
(d) 0.25 s

B

Question. Horizontal component of earth’s field at a height of 1 m from the surface of earth is H. Its value at a height of 10 m from surface of earth is
(a) H/10
(b) H/9
(c) H/100
(d) H

D

Question. The work done in turning a magnet of magnetic moment M by an angle of 90° from the meridian, is n times the corresponding work done to turn it through an angle of 60°. The value of n is given by
(a) 2
(b) 1
(c) 0.5
(d) 0.25

A

Question. Iron is ferromagnetic
(a) above 770°C
(b) below 770°C
(c) at all temperature
(d) above 1100°C

B

Question. If a magnet is suspended at angle 30º to the magnetic meridian, the dip needle makes an angle of 45º with the horizontal. The real dip is
(a) tan-1 (√3/√2)
(b) tan-1 (√3)
(c) tan-1 (√3/2)
(d) tan-1 (2/√3)

D

Question. A steel wire of length l has a magnetic moment M. It is bent in L-shape (Figure). The new magnetic moment is

(a) M
(b) M/√2
(c) M/2
(d) 2M

B

Question. 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) directed perpendicular to the plane of paper
(b) zero
(c) directed along OP
(d) directed along PO

B

Question. A toroid of n turns, mean radius R and cross-sectional radius a carries current I. It is placed on a horizontal table taken as xy-plane. Its magnetic moment m
(a) is non-zero and points in the z-direction by symmetry
(b) points along the axis of the toroid (m = mf)
(c) is zero, otherwise there would be a field falling as 1/r3 at large distances outside the toroid

C

Question. The magnetic field of the 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 the earth. At Mumbai, declination is nearly zero. Then,
(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 the earth axis passes through Greenwich
(d) declination averaged over the earth must be always negative

A

Question. In a permanent magnet at room temperature.
(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

D

Question. A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B. If a force F is experienced by each pole of the magnet, the length of the magnet will be
(a) F/MB
(b) MB/F
(c) BF/M
(d) MF/B

B

Question. Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnet ic dipole moment m r . Which configuration has highest net magnetic dipole moment ?

(a) A
(b) B
(c) C
(d) D

C

Question. The magnetic susceptibility is negative for :
(a) diamagnetic material only
(b) paramagnetic material only
(c) ferromagnetic material only
(d) paramagnetic and ferromagnetic materials

A

Question. If θ1 and θ2 be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip q is given by :-
(a) tan2θ = tan2q1 + tan2θ2
(b) cot2θ = cot2q1 – cot2θ2
(c) tan2θ = tan2q1 – tan2θ2
(d) cot2θ = cot2q1 + cot2θ2