In physics, Coulomb’s law is a law of electrostatics that describes the electrostatic force between electrically charged particles. The force is attractive if the charges have opposite signs and repulsive if they have the same character. The magnitude of this force is directly proportional to the product of the magnitudes of each charge and inversely proportional to the square of their separation distance. This relationship was first published by French physicist Charles-Augustin de Coulomb in 1785 as an empirical observation.
Coulomb’s law can be used to calculate the electric field generated by a point charge, provided that its surroundings are uniform (that is, there are no other charges nearby). It can also calculate how strong an electrostatic force will be between two-point charges; however, other methods must be used for more complicated situations involving non-uniform fields or multiple charges (such as Gauss’s law). Despite its simplicity, Coulomb’s law provides a good approximation for many real-world cases involving electrical forces. The SI unit for electric charge is coulombs (C), which represents 6.241×10^18 electrons (or protons). One electron has a charge of −1e; one proton has a charge of +1e.
One ampere is also equal to one Coulomb per second, or 6.241 × 10^18 electrons flowing past a given point in one second. i.e., 1 Coulomb = 1 Amp second.