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

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## Magnetism and Matter Class 12 MCQs Questions with Answers

Question 1.
The unit of pole strength is:
(a) Am-1
(b) Am
(c) Am-2
(d) Am²

Question 2.
The angle of dip at a place where the horizontal component of earth’s magnetic field equals the vertical component is:
(a) 45°
(b) 0°
(c) 90°
(d) 30°

Question 3.
Isoclinic lines are the lines joining places of:
(a) equal dip
(b) equal declination
(c) 0° dip and 90° declination
(d) equal dip and declination both

Question 4.
Two identical magnets each of dipole moment M and length 21 are perpendicular to each other as shown in figure here. The dipole moment of the combination is

(a) √2 M
(b) 2M
(c) $$\frac {m}{√2}$$
(d) $$\frac {M}{2}$$

Question 5.
The Hysteresis cycle for the material of permanent magnet should be:
(a) long and thin
(b) short and thin
(c) short and wide
(d) long and wide

Question 6.
A steel wire of length l has a magnetic moment M. It is the bent into a semi circular arc. The new magnetic moment is:
(a) $$\frac {M}{l}$$
(b) M
(c) $$\frac {2}{π}$$
(d) M × l

Answer: (c) $$\frac {2}{π}$$

Question 7.
A magnetic needle lying parallel to a magnetic field requires W units of work to turn in through 60°. The torque needed to maintain the needle in this position will be:
(a) $$\frac {W}{√3}$$
(b) √3W
(c) $$\frac {2}{√3}$$ W
(d) $$\frac {√3}{2}$$ W

Question 8.
The magnetic field due to a small magnetic dipole of magnetic moment M, at a distance r from its centre on the equitorial line is:
(a) $$\frac {µ_0}{4π}$$ $$\frac {M}{r^3}$$
(b) $$\frac {µ_0}{4π}$$ $$\frac {2M}{r^3}$$
(c) $$\frac {µ_0}{4π}$$ $$\frac {2M}{r^2}$$
(d) $$\frac {µ_0}{4π}$$ $$\frac {M}{r^2}$$

Answer: (a) $$\frac {µ_0}{4π}$$ $$\frac {M}{r^3}$$

Question 9.
The magnetic fields strength at a distance d from a short bar magnet in longitudinal and transverse positions are in the ratio.
(a) 2 : 1
(b) 1 : 2
(c) 1 : 1
(d) 3 : 2

Question 10.
A long solenoid has 800 turns per metre length of solenoid. A current of 1.6 A flows through it. The magnetic induction at the end of the solenoid on its axis is:
(a) 32 × 10-4 T
(b) 16 × 10-4 T
(c) 4 × 10-4 T
(d) 8 × 10-4 T

Answer: (d) 8 × 10-4 T

Question 11.
The lines of force due to earth’s horizontal magnetic field are:
(a) Curved lines
(b) elliptical
(c) Parallel and straight
(d) concentric circles.

Question 12.
Domain formation is the necessary feature of
(a) Diamagnetism
(b) Paramagnetism
(c) Ferromagnetism
(d) All of these.

Question 13.
Susceptibility of a magnetic substance is found to depend on temperature and the strength of the magnetising field. The material is a:
(a) Diamagnet
(b) Paramagnet
(c) Ferromagnet
(d) Superconductor.

Question 14.
A uniform magnetic field is obtained in a:
(a) bar magnet
(b) horse shoe magnet
(c) circular coil carrying current
(d) None of these.

Question 15.
A magnetic needle suspended by a silk thread is vibrating in the earth’s magnetic field. If the temperature of the needle is increased of 700°C, then
(a) time period increases.
(b) time period decreases.
(c) time period remains unchanged.
(d) the needle stops vibrating.

Answer: (d) the needle stops vibrating.

Question 16.
Isogonic lines on magnetic map represent lines of:
(a) Zero declination.
(b) equal declination.
(c) equal dip.
(d) equal horizontal field.

Question 17.
At Curie point of ferromagnetic material becomes
(a) Diamagnetic
(b) Paramagnetic
(c) Strongly ferromagnetic
(d) non-magnetic

Question 18.
The absence of magnetic monopole is explained by
(a) Gauss’s law
(b) Coulomb’s law
(c) Lorentz’s Law
(d) Fleming law.

Fill in the Blanks

Question 1.
A wire of length l metre carrying a current I ampere is bent into a circle. The magnitude of the magnetic moment in S.I. system is ………………..

Answer: $$\frac {Il^2}{4π}$$

Question 2.
Lines joining the places having same angle of dip are called as ………………..

Question 3.
Angle between the magnetic meridian and the geographic meridian is called as ………………..

Question 4.
According to the modem theory of magnetism, every atom of a substance behaves just like a ………………..

Question 5.
The vertical component of earth’s magnetic field exists every where except at the ………………..

Question 6.
The electromagnets are made of soft iron because it has ……………….. and ………………..

Question 7.
Soft iron is preferred as the core of transformers due to its ……………….., ……………….., ……………….. and ………………..

Answer: High retentivity, low coercivity, high permeability, low hystersis loss.

Question 8.
Lines joining the places having the same angle of declination are called ………………..

Question 9.
In a hydrogen atom, the electron moves in an orbit of radius 0.5.0 A° making 1016 revolutions per second. The magnetic moment associated with the orbital motion of the electron is ………………..

Question 10.
The area under B-H or I-H loop gives the energy dissipated as heat and is known as hysteresis loss which is equal to ………………..

Answer: loss of energy per unit volume per cycle of magnetisation.

Question 11.
The Angle of dip is 0° at ……………….. and 90° at ………………..

Question 12.
Ampere/metre (Am-1) or Newton per Tesla per metre2 (NT-1m-21) is the S.I. unit of ………………..

Question 13.
Ratio of force applied by the pole of a magnet on a unit north pole to the magnetic induction is called ………………..

Pole strength (m) i.e.,
m = $$\frac {F}{B}$$

Question 14.
S.I. unit of magnetic permeability (µ) is ………………..

Answer: Wb A-1 m-1 or henry/metre (Hm-1).

Question 15.
The potential energy of a magnetic dipole is minimum when it is ……………….. to the magnetic field and maximum when it is ……………….. to the magnetic field.

Question 16.
The magnetic dipole is in the unstable equilibrium when $$\vec{M}$$ and $$\vec{B}$$ are ……………….. and in the stable equilibrium when $$\vec{M}$$ and $$\vec{B}$$ are ………………..

Question 17.
The magnetic field inside a solenoid is ……………….. than inside a bar magnet.

Question 18.
The magnetic field is ……………….. inside a solenoid and ……………….. outside it.