Charles de Coulomb found the law of interaction of point charges in 1784 through experimentation. In SI Coulomb's law can be expressed as

F = (1/4πε_{0})(q_{1}q_{2}/r^{2}) ,

Where ε_{0} = 8.85*10^{-12}C^{2}/Nm^{2} is an electric constant, q_{1} and q_{2} are the magnitudes of point charges, and r is the distance between them. The direction of the vector force F is along the line that connects the charges. If the signs of q_{1} and q_{2} are the same (F > 0) , the force is that of repulsion, and if they are opposite (F < 0) , the force is that of attraction.

The interaction of electric charges that are at rest is called electrostatic.

Note that electrostatic interaction satisfies the principle of superposition.