Magnetic susceptibility is a property of a material that describes how easily it can be magnetized in the presence of an external magnetic field. It is a dimensionless quantity denoted by the symbol χ (chi). The concept of magnetic susceptibility is closely related to the field of magnetism and electromagnetic theory.
In a magnetic circuit, which is analogous to an electrical circuit, you have components like magnetic materials (such as iron cores) and air gaps that can carry magnetic flux. Just as in an electrical circuit you have resistance and conductance, in a magnetic circuit you have reluctance and permeance.
The relationship between magnetic flux (Φ) and magnetic field intensity (H) in a magnetic material is given by:
Φ = B * A = μ * H * A,
where:
B is the magnetic flux density (also known as magnetic induction),
A is the cross-sectional area of the material through which the flux passes,
μ is the permeability of the material, and
H is the magnetic field intensity.
Magnetic susceptibility is defined in terms of the relative permeability (μr) of a material, which is a dimensionless factor that indicates how much the material can be magnetized compared to a vacuum or free space (where μr = 1).
χ = μr - 1.
If a material has a positive magnetic susceptibility (χ > 0), it means that it can be easily magnetized and will strengthen the applied magnetic field. Paramagnetic materials are an example of this, as they have unpaired electrons that align with the external magnetic field.
If a material has a negative magnetic susceptibility (χ < 0), it means that it resists being magnetized and weakens the applied magnetic field. Diamagnetic materials exhibit this behavior, as they have paired electrons that create opposing magnetic moments to an external field.
Ferromagnetic materials, like iron and nickel, have very high positive values of magnetic susceptibility due to the presence of magnetic domains that can align with an external magnetic field, leading to strong magnetization.
It's important to note that the magnetic susceptibility of a material can change with temperature and other factors. Additionally, magnetic susceptibility is a complex quantity, meaning it can have both real and imaginary parts when considering the frequency-dependent behavior in the presence of alternating magnetic fields.
In summary, magnetic susceptibility is a key concept in electromagnetism and is used to describe how easily a material can be magnetized in response to an applied magnetic field, influencing the behavior of magnetic circuits and electromagnetic devices.