Permittivisyys

Permittivity is a physical property of a material that describes how an electric field affects and is affected by that dielectric medium. It essentially quantifies how easily a material can be polarized by an electric field. When an electric field is applied to a material, the charges within the material may shift, creating an internal electric field that opposes the applied field. Permittivity measures the extent to which this opposition occurs.

There are two main types of permittivity. Absolute permittivity, denoted by the Greek letter epsilon (ε), is a fundamental property of the material. It is related to the electric displacement field (D) and the electric field (E) by the equation D = εE. The permittivity of free space, often denoted as ε₀, is a physical constant representing the permittivity of a vacuum. Its approximate value is 8.854 x 10⁻¹² farads per meter.

Relative permittivity, also known as the dielectric constant, is the ratio of the absolute permittivity of a material to the permittivity of free space: εᵣ = ε / ε₀. This dimensionless quantity indicates how much better a material is at storing electrical energy in an electric field compared to a vacuum. Materials with high relative permittivity can significantly reduce the electric field strength within them, making them useful in capacitors and as electrical insulators.