Magnetic Properties of Materials - Class 12 Physics MCQ

This set of Class 12 Physics Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Magnetic Properties of Materials”.

1. Identify the expression for magnetic induction from the following.
a) B = μ_o(H+I)
b) B = μ_o(H×I)
c) B = μ_o(H-I)
d) B = μ_o(\(\frac {H}{I}\))
View Answer

Answer: a
Explanation: Magnetic induction (B) is defined as the number of magnetic lines of induction crossing per unit area normally through the magnetic substance, and is given by:
B = μ_o(H+I)
The SI unit of magnetic induction is Tesla (T).

2. Which among the following is true about magnetic susceptibility?
a) It is the ratio of magnetic intensity to intensity of magnetization
b) The SI unit of magnetic susceptibility is Tesla (T)
c) It is the ratio of intensity of magnetization to magnetic intensity
d) It is the ratio of magnetic moment to volume
View Answer

Answer: c
Explanation: Magnetic susceptibility of a magnetic substance is defined as the ratio of the intensity of magnetization (I) to the magnetic intensity (H). The expression is given by:
χ_m=\(\frac {I}{H}\)
Magnetic susceptibility measures the aptness of a magnetic substance to acquire magnetism. It is a unit less constant of magnetic substance.

3. Pick out the unit of magnetic permeability.
a) TmA
b) \(\frac {Tm}{A}\)
c) \(\frac {T}{mA}\)
d) \(\frac {Am}{T}\)
View Answer

Answer: b
Explanation: Magnetic permeability (μ) of a magnetic substance is defined as the ratio of its magnetic induction (B) to the magnetic intensity (H). The expression for magnetic permeability is given as:
μ=\(\frac {B}{H}\)
Magnetic permeability is the ability of a magnetic substances to permit magnetic field lines to pass through it. The SI unit for this quantity is \(\frac {Tm}{A}\).

4. Relative magnetic permeability is unit less.
a) True
b) False
View Answer

Answer: a
Explanation: Yes, relative magnetic permeability is a unit less constant of magnetic substance. Relative magnetic permeability (μ_r) of a magnetic substance is defined as the ratio of its magnetic permeability to the permeability of free space. The expression for it is given as:
μ_r=\(\frac {μ}{\mu_o}\)

5. The relative permeability of a medium is 0.050. What is its magnetic susceptibility?
a) 500
b) 501
c) 49.9
d) 499
View Answer

Answer: d
Explanation: Given: relative permeability (μ_r) = 500
Required equation ➔ μ_r = 1+χ_m
χ_m = μ_r – 1
χ_m = 500 – 1
χ_m = 499
Therefore, the value of magnetic susceptibility is 499.

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6. The magnetic susceptibility of a paramagnetic material at -80⁰C is 0.0085, then what is its value at -180⁰C?
a) 0.015
b) 0.016
c) 0.017
d) 0.018
View Answer

Answer: c
Explanation: Given: χ_m1 = 0.0085; T₁ = -80⁰ C = -80 + 273 = 193 K; T₂ = -180⁰ C = -180 + 273 = 93 K
χ_m ∝ \(\frac {1}{T}\)
\(\frac {\chi_{m2}}{\chi_{m1}} \, = \, \frac {T_1}{T_2}\)
\(\frac {\chi_{m2}}{0.0085} \, = \, \frac {193}{93}\)
χ_m2 = \(\frac {193 \, \times \, 0.0085}{93}\)
χ_m2 = 0.017

7. A material has a permeability of 0.1 H/m when the magnetic intensity is 70 A/m. What will be the magnetic induction inside the material?
a) 7 T
b) 0.7 T
c) 70 T
d) 0.07
View Answer

Answer: a
Explanation: Given: permeability (μ_o) = 0.1 H/m; Magnetic intensity (H) = 70 A/m
Required equation ➔ Magnetic induction (B) = μ_o × H
B = 0.1 × 70
B = 7 T
Therefore, the magnetic induction inside the material is 7 T.

8. Ferromagnetic materials does not show hysteresis.
a) True
b) False
View Answer

Answer: b
Explanation: Ferromagnetic materials do show hysteresis. When a ferromagnetic material is magnetized in one direction, it will not relax back to zero magnetization when the imposed magnetizing field is removed. The phenomenon of hysteresis in ferromagnetic materials is the result of two effects ➔ rotation of magnetization and changes in size or number of magnetic domains.

9. Find the correct combination regarding relative permeability and magnetic susceptibility of a paramagnetic substance.
a) μ_r > 1, χ < 0
b) μ_r < 1, χ > 0
c) μ_r < 1, χ < 0
d) μ_r > 1, χ > 0
View Answer

Answer: d
Explanation: The correct combination for paramagnetic substances is given as follows:
μ_r > 1, χ > 0
Paramagnetic materials have a small and positive value of magnetic susceptibility (χ). The relative permeability (μ_r) of paramagnetic materials is just greater than 1.

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