Permittivity applies to all materials with permeability to electric fields; equally to solid, liquid and gaseous materials. It is a dimensionless unit from the system of units( SI) with the formula symbol small epsilon 'epsilon'. Permittivity values are relative values that are related to the electric field constant epsilon-zero. Epsilon-zero is the permittivity for vacuum.
The permittivity has a direct influence on the properties of dielectrics and thus, for example, on the characteristic values of capacitors, ceramic filters, on cables, strip lines or microstrips. The permittivity expresses how much greater certain characteristic values are compared to a vacuum. In the case of capacitors, the permittivity indicates how much greater the capacitance of a capacitor is when another material of the same thickness is used as the dielectric instead of air. Air thus forms the reference for the dielectric constant (DK) and has the value `epsilon` = 1.
Permittivity values can be in the single digits, as with paper, hard rubber, glass, and the plastics polyethylene terephthalate( PET), polypropylene( PP), polystyrene( PS), and polyvinyl chloride( PVC); other materials such as polyamide( PA), special ceramics, and oxides have permittivity values in the multi- digit range. Barium titanate( BaTiO3) is a ferroelectric and has a dielectric constant in the five-digit range.
The permeability of materials to magnetic fields is the permeability.