Electric permittivity and dielectric constant

- table or chart of the electric permittivity or dielectric constant of a material. This figure is important because it determines the capacitance between two plates. One of the factors

The permittivity is another term for the dielectric constant or a material. It is that property of a dielectric material that determines how much electrostatic energy can be stored per unit of volume when unit voltage is applied.

Substance	Relative Permittivity
Ebonite	2.7 - 2.9
Glass	5 - 10
Marble	8.3
Mica	5.6 - 8.0
Paraffin wax	2 - 2.4
Porcelain	4.5 - 6.7
Rubber	2.0 - 2.3
Calcium titanate	150
Strontium titanate	200
Air 0C	1.000594
Air 20C	1.000528
Carbon monoxide 25C	1.000634
Carbon dioxide 25C	1.000904
Hydrogen 0C	1.000265
Helium 25C	1.000067
Nitrogen 25C	1.000538
Sulphur dioxide 22C	1.00818

The values given above are what may be termed the "static" values of permittivity. They are true for steady state or low frequencies. It is found that the permittivity of a material usually decreases with increasing frequency. It also falls with increasing temperature. These factors are normally taken into account when designing a capacitor for electronics applications. Some materials have a more stable level of permittivity and hence they are used in the higher tolerance capacitors. However this often has to be balanced against other factors. Some materials have very high levels of permittivity, and hence they enable capacitors to be made much smaller. This factor may be particularly useful when the size of the capacitor is particularly important.