ELECTRIC PERMITTIVITY OF MEDIUM
Electric permittivity (dielectric constant) of medium ε is a dimensionless value, which characterizes insulating properties of the medium. It shows, how many times less is the interaction between charges in a homogeneous medium than in vacuum. Electric permittivity of the air is close to the electric permittivity of vacuum ε0, that is, to one. Dielectric constant of water is rather high, about 80.