# Physics Questions and Answers – Magnetisation and Magnetic Intensity

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This set of Physics MCQs for Class 12 focuses on “Magnetisation and Magnetic Intensity”.

1. Identify the expression for magnetic intensity from the following.
a) H = $$\frac {B_o}{\mu_o}$$
b) H = Bo × μo
c) H = $$\frac {2B_o}{\mu_o}$$
d) H = $$\frac {B_o}{2\mu_o}$$

Explanation: Magnetic intensity in vacuum is defined as the ratio of applied magnetic field (Bo) to the permeability of free space (μo). Magnetic intensity is denoted by H. The expression is given by:
H = $$\frac {B_o}{\mu_o}$$

2. Pick out the expression for intensity of magnetization from the following.
a) I = $$\frac {M^2}{V}$$
b) I = $$\frac {M}{V^2}$$
c) I = $$\frac {V}{M}$$
d) I = $$\frac {M}{V}$$

Explanation: Intensity of magnetization is defined as the magnetic moment developed per unit volume, when a magnetic specimen is subjected to the magnetizing field. Intensity of magnetization is denoted by I. The expression is given by:
I=$$\frac {M}{V}$$

3. Which of the following is another term for magnetization?
a) Magnetic neutrality
b) Magnetic polarization
c) Magnetic power
d) Magnetic moment

Explanation: Magnetization is also termed as magnetic polarization. Magnetic polarization is basically a balance between the magnetic flux density in a space which is devoid of matter and the magnetic flux density in a space with matter, i.e. in a material.

4. Both magnetization and magnetic intensity have the same unit.
a) True
b) False

Explanation: Both magnetization and magnetic intensity have the same unit ➔ A/m.
Magnetic intensity (H) = $$\frac {B_o}{\mu_o}$$
B = $$\frac {current}{length}$$ (ampere circuital law) ➔ unit of B0 = $$\frac {A}{m}$$; μ0 is dimensionless as it is a constant. Therefore, the unit of H is the same as B0.
Magnetization (I) = $$\frac {M}{V}$$
I = $$\frac {Magnetic \, moment}{Volume}$$ ➔ Unit of magnetic moment = Am2; Unit of volume = m3; I = $$\frac {Am^2}{m^3} = \frac {A}{m}$$
Thus, the units of magnetization and magnetic intensity is the same.

5. Find the false statement.
a) Magnetic intensity is a vector quantity
b) Induced magnetization is a process where you can magnetize a non-magnetic material
c) Magnetic intensity and intensity of magnetization are the same.
d) Total intensity is the measurement from the magnetometer after a model of the earth’s normal magnetic field is removed

Explanation: The statement magnetic intensity and intensity of magnetization are the same is the false one. They are not the same. When a magnet is entering a magnetic field, then the poles of the magnet experiences certain forces. Magnetic intensity refers to the measure of these forces. But, the intensity of magnetization explains the change in the magnetic moment of a magnet as a function of volume. All the other statements are valid. 