Question

The ratio of intensity of magnetization and magnetizing field is called:
A. Permeability.
B. Magnetic induction.
C. Magnetic intensity.
D. Magnetic susceptibility.

Answer 1

Hint: Any magnetic material possesses a magnetic moment. The magnetic moment of a magnetized material per unit volume of the material is termed as the intensity of magnetization denoted by $$M$$. The magnetic field strength that arises in material from an external source and is not an intrinsic property of the material is referred to as magnetizing field intensity. It is denoted by the vector $$H$$.

Complete step by step answer:
The ratio of the intensities of magnetization and magnetizing field gives the strength of the magnetic material to get magnetized in a unit magnetizing field. Permeability is the measure of the resistance to this field and magnetic induction is the principle of how an object gets magnetized. The force experienced by a unit north pole at a point gives the magnetic intensity at that point. The ratio of $$M$$ to $$H$$ is hence coined to the term Magnetic susceptibility which gives the measure of how much a material will be magnetized in an applied magnetizing field. Magnetic susceptibility is symbolized as $${\chi }_m$$.
$${\chi }_m={\displaystyle \frac{M}{H}}$$
Therefore the correct option is D.

Additional information:
When a material can interact with a magnetic field to produce a mechanical moment or mechanical positional force, the material is said to possess a magnetic moment. The value of magnetic susceptibility determines whether the material is paramagnetic or diamagnetic. This susceptibility is determined for rocks which help in their classification. Alloys with high positive susceptibility are made to make permanent magnets e.g.: Alnico.

Note: Similar to magnetic susceptibility there is electrical susceptibility. Paramagnetic materials have Positive susceptibility and their domains align along the applied field direction. Diamagnetic material has negative susceptibility and their donation align opposite to the applied field direction. The ratio questions should be read properly as the inverse will give another property of the material. Magnetizing fields and magnetization have two different meanings. Candidates are advised to use it appropriately.