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Question Bank [ 2022 ] — Physics STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsQuestion Bank [ 2022 ]4 Marks
Question
Define magnetization. State its SI unit and dimensions. Derive the relation between magnetic field intensity(H) and magnetization(M) for a magnetic material placed in a magnetic field.
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Answer

i. The ratio of magnetic moment to the volume of the material is called magnetization.
ii. Unit: $Am ^{-1}$ in $SI$ system.
iii. Dimensions: $\left[ M ^0 L ^{-1} T ^0 I ^1\right]$
iv. Relation between magnetic field intensity $( H )$ and magnetization(M):
a. Consider a magnetic material (rod) placed in a magnetizing field (solenoid with $n$ turns per unit length and carrying current I).
b. The magnetic field inside the solenoid is given by, $B _0=\mu_0 nl \ldots .(1)$
Where $\mu_0=$ permeability of free space.
c. The magnetic field inside the rod is given as, $B _{ m }=\mu_0 M \ldots$...(2)
Where $M=$ magnetization of the material
d. The net magnetic field inside the rod is expressed as,
$ B = B _0+ B _{ m } \ldots .(3)$
$\therefore B =\mu_0 nl +\mu_0 M$
$\therefore B =\mu_0 H +\mu_0 M $
Where $H = nl =$ Magnetic field intensity
$ \therefore B=\mu_0(H+M)$
$\therefore H=\frac{B}{\mu_0}-M . $
e. Equation (4) shows that the magnetic field (B) induced in the material depends on magnetic field intensity $( H )$ and magnetization (M).

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