An electric force exists between any two charged particles. On observation, it is found that the mutual forces on the particles may be either attractive or repulsive, depending on the types of charges (+ or -). In fact, it is because of these different force interactions that we know there are two different types of charges.
Law of charges
The attraction and repulsion between different types of charges are described by the law of charges: Like charges repel; unlike charges attract.
In other words, two negative charges (charged particles) or two positive charges experience repulsive electric forces. A positive charge and a negative charge experience attractive forces.
Difference between the law of charges & Coulomb’s law
The law of charges gives the direction of an electric force, but it doesn’t say anything about the magnitude of the electric force.
Charles Coulomb derived a relationship for the magnitude of the electric force between two charged bodies that is appropriately known as Coulomb’s law.
Coulomb’s law states that the force of attraction or repulsion between two charged bodies is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.
This can be written in equation form as follows:
Force = (constant x charge 1 x charge 2)/(distance between charges)2
F = kQ1Q2/r2
where F is the magnitude of the force in newtons, k is a constant, Q1 the magnitude of the first charge in coulombs, Q2 the magnitude of the second charge in coulombs, and r the distance between the charges in meters. Here k is a proportionality constant with the value of
k=9 x 109 Nm2/C2