Permittivity

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Measure of how an electric field affects, and is affected by, a dielectric medium

Permittivity is a fundamental physical quantity that describes how an electric field affects, and is affected by, a dielectric medium. It is a measure of the ability of a material to store electrical energy in an electric field. The permittivity of a material determines how much electric field (or electric flux) is 'permitted' to pass through the material.

Definition

Permittivity is denoted by the symbol ε. The SI unit for permittivity is the farad per meter (F/m). The permittivity of free space, also known as the vacuum permittivity, is a physical constant denoted by ε₀. The relative permittivity, also known as the dielectric constant, is the ratio of the permittivity of a material to the permittivity of free space.

Mathematical Expression

The permittivity ε of a material can be expressed as: \[ \varepsilon = \varepsilon_0 \varepsilon_r \] where:

• \(\varepsilon_0\) is the vacuum permittivity (approximately \(8.854 \times 10^{-12} \, \text{F/m}\))
• \(\varepsilon_r\) is the relative permittivity of the material

Vacuum Permittivity

The vacuum permittivity, ε₀, is a fundamental physical constant that characterizes the permittivity of free space. It is a key parameter in Maxwell's equations and plays a crucial role in the propagation of electromagnetic waves.

Relative Permittivity

The relative permittivity, εᵣ, also known as the dielectric constant, is a dimensionless quantity that describes how much a material can polarize in response to an electric field, relative to the vacuum. It is given by: \[ \varepsilon_r = \frac{\varepsilon}{\varepsilon_0} \]

Applications

Permittivity is a critical parameter in various fields of physics and engineering, including:

• Electromagnetism
• Capacitance and capacitors
• Dielectric materials
• Wave propagation
• Optics

See Also

• Dielectric
• Electric field
• Electromagnetic wave
• Maxwell's equations
• Capacitance
• Farad

References

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