Definition of One Coulomb- One coulomb is that charge which repels an equal and similar charge with a force 9x10⁹ N, when placed in vacuum(or air) at a distance of one meter from it.

                                    1C= 3x10⁹ stat C

Principle of superposition--

It states that when a number of charges are interacting,

total force on a given charge is the vector sum of the

individual forces exerted on the given charge by all

 the other charges. The force between any two charges

 is not affected by the presence of other charges.

Net force on the charge q is F=F₁+F₂+F₃....