Difference between Permittivity and Permeability

There are two physical quantities namely Permittivity and Permeability that play a vital role in the field electrical engineering.

• Permittivity is related to electrostatics and it is the measure of electrical polarization of a dielectric material when it is placed in an external electric field.

• Permeability is related to electromagnetism and it is the measure of magnetic polarization of a magnetic material when it is placed in an external magnetic field.

In this article, we will highlight all the key differences between permittivity and permeability by considering different parameters like basic definition, unit, formula, importance, etc. Let's start with some basics so that it becomes easy to understand the differences between them.

What is Permittivity?

The measure of electric polarization of a dielectric material under the influence an electric field is known as permittivity. The permittivity is denoted by the Greek letter epsilon (ε) and is measured in Farad per meter (F/m).

In electrostatics, the permittivity of a material plays a very important role where it help in determining the electrostatic force between charged bodies, in calculating the capacitance of a capacitor, in calculating energy storage capacity of a dielectric medium, etc. The permittivity of a dielectric medium is given by,

$$\varepsilon\:=\:\varepsilon_o\varepsilon_r$$

Where, 𝜀_o and ε_r are the permittivity of free space and the relative permittivity of the dielectric medium respectively. Where,

$$\varepsilon_o\:=\:8.85\:\times\:10^{-12}\:F/m$$

The permittivity of a material gives the information about how easily the material allows the flow of electric field through it.

What is Permeability?

Permeability is the measure of magnetization of a material in response to an applied magnetic field. It is also known as magnetic permeability. The permeability determines the degree in which a magnetic material modifies the magnetic flux in a region occupied by the material in a magnetic field.

The magnetic permeability is denoted by a Greek letter mu (μ) and it is measured in Henry per meter (H/m) in SI system. The absolute permeability of a material is given by,

$$\mu\:=\:\mu_o\:\mu_r$$

Where, μ0 is the permeability of free space or vacuum and it is equal to 4π × 10^-7 H/m. The μ_r is the relative permeability of the material. The permeability of a material gives information about the ease in the flow of magnetic flux through the material, i.e. it tells about how easily the magnetic flux can be established in a material.

Difference between Permittivity and Permeability

The major differences between permittivity and permeability are listed in the following table

Basis of Difference	Permittivity	Permeability
Definition	The measure of electric polarization of an insulating or dielectric material when it is subject to an electric field is known as permittivity.	The measure of ability of a magnetic material to allow the flow of magnetic flux is known as permeability.
Denotation	Permittivity of a dielectric material is denoted by the Greek letter epsilon (ε).	Permeability of a magnetic material is denoted by the Greek letter mu (μ).
Physical meaning	Permittivity means the ability of a material to electrically polarize in response to an externally applied electric field.	Permeability means the ability of a material to magnetize in response to an externally applied magnetic field.
Formula	The permittivity of a dielectric medium is given by, $$\varepsilon\:=\:\varepsilon_o\varepsilon_r$$	The permeability of magnetic material is given by, $$\mu\:=\:\mu_o\:\mu_r$$
SI unit	The SI unit of permittivity is Farad per meter (F/m).	The SI unit of permeability is Henry per meter (H/m).
Types	The permittivity of a material is of two types namely relative permittivity (εr) and absolute permittivity (ε).	The permeability of a material
Field to which related	The permittivity of a material is the property related to electric field	The permeability is the property of a material that is related magnetic field.
Value in free space or vacuum	The value of permittivity of free space or vacuum is equal to 8.85 × 10−12 F/m.	The value permeability of free space or vacuum is equal to 4π× 10−7H/m.
Referred as	Permittivity of a material is referred as the dielectric constant of the material.	Permeability of a material is referred as the magnetic constant.
Applications	Permittivity is used in different calculation of electrostatics such as for calculating force between two charges, capacitance, electric field density and intensity, etc.	Permeability is used in electromagnetic calculations like magnetic field intensity, magnetic field density, selection of core for electromagnetic devices, etc.

Conclusion

The most significant difference that you should note here is that Permittivity is the measure of response of a material towards the electric field, while Permeability is the measure of response of a material towards the magnetic field. Both quantities are extensively used in several electrical related calculations.