how does coulomb force between two point charges depend upon the permitivity of the intervening medium ?
The Coulomb Force between two charges decreases when a dielectric medium is placed in between the charges. The dielectric reduces the electrostatic force as compared to vacuum by a factor εr called the dielectric constant of the medium. This factor is also know as the relative primitivity of the medium.
The electrostatic force between two charges q1 and q2 separated by a distance r in a medium of dielectric constant εr is given by,