Unit: farad meter-1 (F m-1)
The permittivity of a substance is a characteristic which describes how it affects any electric field set up in it. A high permittivity tends to reduce any electric field present. We can increase the capacitance of a capacitor by increasing the permittivity of the dielectric material.
The permittivity of free space (or a vacuum), e0, has a value of 8.9 × 10-12 F m-1.
The permittivity of a material is usually given relative to that of free space, it is known as relative permittivity, er. Permittivity is then calculated
by multiplying e0 by this figure.
Relative permittivity, er
|Vacuum||1 (by definition)|
We can increase the capacitance of a capacitor by increasing the permittivity of the dielectric material.