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 formula:**

Permittivity = Electric Displacement/Electric Field density

SI unit of permittivity is Farad/metre.

**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, ε r = 0

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 = FaFm

Where Fa =14Π0 q1q2r2

Fm = 14Π ε0rq1q2r2

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**Dimensional formula of permittivity**

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

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 permeabilityis 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 |

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.

**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 = 0

Where μr is a dimensionless quantity.

Comparison of permittivity and permeability

Comparison Parameters | Permittivity | Permeability |

Definition | It is the measure of 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 F/m | 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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