We've all had fun with magnets as kids. Some of us are now even playing with them! What makes them magnetic though? Why aren't there magnetic fields in all materials and substances? Have you ever given it any thought? The subjects of magnetization and magnetic intensity will be covered in this chapter.
It also takes into account any imbalanced magnetic dipole moment that the material may have due to the mobility of its electrons, as previously indicated. The idea of magnetization aids in the classification of materials according to their magnetic properties.
We'll learn more about magnetization and the idea of magnetic intensity in this part. The arrangement of the atoms inside a material determines a magnet's magnetic behaviour. This is what we'll be discussing in this article. The magnetization (M) of the material is equal to the net magnetic moment per unit volume of that material.
In terms of mathematics,
M = mnet ⁄ V
Let's take a look at the case of a solenoid. If we consider a solenoid with n turns per unit length and a current I flowing through it, the magnetic field in the solenoid's interior may be expressed as,
B0 = μ0 n I
where, µ0 is the constant permeability of a vacuum.
If we fill the solenoid's inside with a non-zero magnetization material, the field within the solenoid must be higher than before. Inside the solenoid, the net magnetic field B may be written as,
B = B0 + Bm
where, Bm is the field provided by the core material.
It is proportional to the material's magnetization in this case. In terms of mathematics,
Bm = μ0 M
Let us now look at another concept: a material's magnetic intensity. A material's magnetic intensity can be expressed as,
H = (B ⁄ μ0) − M
The total magnetic field may alternatively be defined as, as shown by this equation.
B = μ0 (H + M)
H denotes the magnetic field owing to external variables such as the current in the solenoid, whereas M denotes the magnetic field due to the nature of the core. The latter amount, M, is influenced by external factors and is given by.
M = χ H
where, χ is the material's magnetic susceptibility.
Magnetic susceptibility is a measurement of a material's reaction to an external field. For paramagnetic materials, the magnetic susceptibility is small and positive, while for diamagnetic materials, it is tiny and negative.
Substitute the value of M in the equation of B.
B = μ0 (H + χ H) = μ0 (1 + χ) H
= μ0 μr H = μ H
Here, μr is the relative magnetic permeability of the material which is comparable to the dielectric constants in electrostatics. The magnetic permeability is defined as follows:
μ = μ0 μr = μ0 (1 + χ)
The force that a unit north – pole experiences when it is put in a magnetic field is described as the magnetic intensity at that location. The magnetic field strength at P owing to a single pole is given by:
where, m is the pole strength.
The +⁄-m is the magnitude of the south and north poles, respectively. r is the distance between point P and the magnet's centre. The length of the bar magnet is denoted by the letter l. The magnetic field intensity at point P is given by:
where, M is the magnetic moment and (2ml) is the length of the magnetic moment.