Permittivity and Permeability - Meaning, Formula, Comparison, FAQs

Permittivity and Permeability - Meaning, Formula, Comparison, FAQs

Edited By Vishal kumar | Updated on Sep 24, 2024 01:10 PM IST

What is permittivity?

Permittivity Meaning: It is the property of every substance that determines the amount of resistance it provides to the production of an electric field. The Greek alphabet ε is used to represent it. It indicates how many charges are necessary to produce one unit of electric flux in a given material.

Permittivity and Permeability - Meaning, Formula, Comparison, FAQs
Permittivity and Permeability - Meaning, Formula, Comparison, FAQs

SI unit of permittivity is Farad/metre.

Also read -

Relative permittivity

The vacuum represents the lowest possible permittivity value. This is also known as the electric constant or permittivity of free space. The value of 8.85 × 10-12 Farad/meter is denoted by the ε0. The resistance to the production of electric field lines can also be seen in dielectrics. A dielectric's permittivity is defined as the ratio of its absolute permittivity to its electric constant, which is referred to as relative permittivity. It is a dimensionless quantity that is expressed as:

Relative Permittivity, εr = ε/ε0

Where ε – absolute permittivity of the material

ε0 – Permittivity of Free Space

εr– relative permittivity

Relative vacuum permittivity (εr) can be used to compute the amount of the electrostatic force between two point charges q1 and q2 separated by a distance r in free space using Coulomb's law. The electrostatic force (Fa) between two point charges separated by a specific distance in air or vacuum is compared to the electrostatic force (Fm) between the same two point charges separated by the same distance in a medium. It's written like:

εr = Fa/Fm

Where

\\F_A=\frac{1}{4\pi \epsilon_0}\frac{q_1q_2}{r^2}\\\\F_B=\frac{1}{4\pi \epsilon_0\epsilon_r}\frac{q_1q_2}{r^2}



Dimensional formula of permittivity

The dimensional formula of permittivity of free space is [M-1L-3T4A2].

What is permeability?

Permeability is the ability of a material to allow the formation of magnetic lines of force or magnetic fields within it in electrostatics. It refers to a material's ability to magnetise in response to an applied magnetic field. In simpler terms, magnetic permeability can be defined as "the extent to which magnetic field lines can enter a substance." or "the power of a substance to conduct magnetic field lines." The Greek alphabet μ is used to represent it. The table below shows the mathematical representation of permeability, as well as the SI unit and dimensional formula: The value of permeability is given by:

Formula
Permeability = Magnitude of magnetic induction (B)/Intensity of magnetic field (H)
Dimension formula
[MLT-2A-2]
SI Unit
H/m or TmA-1
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The Permeability constant measures the permeability of free space and has a value of μ0 = 4π× 10-7 H/m. Magnetic permeability is a key factor in classifying a material's magnetization property. If the magnetic permeability of a substance is less than μ0, it is said to be diamagnetic. Similarly, if the magnetic permeability of a substance is more than μ0, it is said to be paramagnetic.

NCERT Physics Notes:

Magnetic permeability

The magnetic permeability of a material is defined as the ability of the substance to enable a magnetic line of force to pass through it. Magnetic permeability is measured in Henry per metre (SI units).

Magnetic permeability formula

The ratio of flux density to magnetic force, or magnetic permeability, is defined as:

μ = BH

Absolute permeability

Absolute permeability is a constant value that is related to the permeability of free space and is written as:

μ0 = 4π× 10-7 H/m

Relative permeability

The ratio of absolute permeability of magnetic material to absolute permeability of air is defined as relative permeability for a magnetic material.

Relative Permeability, μr = μ/μ0

Where μr is a dimensionless quantity.

Comparison of permittivity and permeability

Also read :

Comparison Parameters
Permittivity
Permeability
Definition
It is the measure of the resistance offered by any material against the formation of an electric field
It is a measurement of how far magnetic field lines may penetrate a substance.
Formula
Permittivity = Electric DisplacementElectric Field density

Permeability = Magnitude of magnetic induction (B)Intensity of magnetic field (H)
Symbol
ε
μ
SI Unit
Farad/metre or F/m
Henries/metre or H/m
Value in free space
ε0 = 8.85 × 10-12 Farad/meter
μ0 = 4π× 10-7 H/m
Principle Involved
Polarisation of electric charges
Magnetisation
Field
Electric Field
Magnetic Field
Application
In capacitors
In transformer core and inductors

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Frequently Asked Questions (FAQs)

1. The ratio of permittivity of medium to the permittivity of free space is known as _____________?

The ratio of permittivity of medium to the permittivity of free space is known as  relative permittivity.

2. What is the SI unit of permittivity?

The SI unit of permittivity if Farad/metre.

3. What is the permittivity of free space?

The permittivity of free space, ε0 = 8.85 × 10-12 Farad/meter

4. The relative permeability of vacuum is ______?

The relative permeability of vacuum is 1.

5. What is the dimensional formula of the relative permittivity?

The  relative permittivity is a dimensionless quantity

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