ELECTROSTATIC FORCE

When two surfaces rub each other then the stationary charges have got charged and then they would transform from one surface to another. The charges are evenly distributed from one place to another.This force is called electrostatic force.

Coulombs law

It states that the force of attraction is directly proportional to the product of two  charges and inversely proportional to the square of the distance between them.

F= kq'q/r^s here, k is the constant of proportionality and its value can be found by the expression i.e k= 1/4pi€ 

Permitivity can be found in free space and in vacuum by using the relation.