Hello, We are being taught about coulomb's law, my teacher said that the constant in the law which we denoted by k, changes with change in medium because of permittivity of the medium. But why does the constant changes unlike the gravitational constant which does not change with medium although the nature and formula of the force are similar? according to the super position theory( which I read in fundamentals of physics - Resnick Halliday and walker) that the charged particles interact independently by coulombs force like the masses in gravitational force, then why the medium affects the coulombs force while not the gravitational force? Sorry for my amateurish language. And thanks in advance..