(n): The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.1
Dielectric constant is best described as how well an electrical signal moves through the insulation material used to cover bare wire. It’s measuring the amount of air in the material that insulates the conductor (also known as relative permittivity).
The closer you can get to the dielectric constant of air (just over 1), the better. Of the standard fluoropolymers used in the wire and cable industry we rely pretty heavily on expanded PTFE (Polytetrafluoroethylene).
The dielectric constant of ePTFE ranges between 1.40 – 2.05 depending on how much air is introduced into it, with standard PTFE coming in at 2.10. FEP and PFA follow suit coming in around 2.10 as well.