What is relative permittivity?
Answers
Relative permittivity (k) is a dimensionless ratio of a substance's permittivity versus vacuum with an applied DC electric field. If you have a parallel plate capacitor in a vacuum with capacitance of Cv and then place the test substance between the plates, the parallel plate capacitor will now have a capacitance of k*Cv. Relative permittivity is always greater than one for matter. Relative permittivity is most commonly associated with poor electrical conductors or insulators. Since metals exclude an internal static electrical field, the DC permittivity of metals is infinite.
The relative permittivity of a substance is a measure of how the atoms and molecules of a substance respond to an externally-applied electrical field. When the applied electrical field is constant (DC), k is simply a number. However, if a time-varying electrical field is applied, the permittivity will be complex - it will have a reactive (lossless) part and a lossy (resistive) part, and both will be a function of the applied frequency and the structure of the material. By measuring the reactive and lossy portions at various frequencies, it is often possible to identify various parts of the internal structure of an insulating substance - a process called dielectric spectroscopy.
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Answer:
Relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum. Likewise, relative permittivity is the ratio of the capacitance of a capacitor using that material as a dielectric, compared with a similar capacitor that has vacuum as its dielectric