What is absolute and relative permeability?

Absolute Permeability:
Absolute permeability, denoted as μ, is a property that describes the ability of a material to allow the flow of magnetic flux. It is primarily used in the context of magnetism and electromagnetism. Absolute permeability is a constant for a given material and is typically measured in henries per meter (H/m) or tesla meters per ampere (T·m/A).

In electromagnetism, absolute permeability is used in Ampere's law to determine the magnetic field generated by an electric current. It relates the magnetic field strength (H) to the magnetic flux density (B) in a material:

B = μH

where B is the magnetic flux density and H is the magnetic field strength.

Relative Permeability:
Relative permeability, denoted as μᵣ, is a dimensionless quantity that compares the permeability of a material to the permeability of a reference material, usually vacuum or free space. It represents how easily a material can be magnetized compared to the reference material.

Relative permeability is the ratio of the absolute permeability of a material (μ) to the absolute permeability of vacuum (μ₀) or free space:

μᵣ = μ / μ₀

Since the permeability of vacuum is constant, the relative permeability of a material can vary. Relative permeability is a key parameter in determining the magnetic properties of materials, such as their ability to concentrate or repel magnetic fields.

In summary, absolute permeability is an intrinsic property of a material that describes its ability to allow the flow of magnetic flux, while relative permeability compares the permeability of a material to that of a reference material, typically vacuum or free space.