Coulomb's law, is sometimes called the Coulomb law, is an equation describing the electrostatic force between electric charges. It was studied and first published in the 1780s by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism. Nevertheless, the dependence of the electric force with distance (inverse square law) had been proposed previously by Joseph Priestley and the dependence with both distance and charge had been discovered, but not published, by Henry Cavendish, prior to Coulomb's works. The magnitude of the electrostatic force between two point electric charges is directly proportional to the product of the magnitudes of each of the charges and inversely proportional to the square of the total distance between the two charges. The scalar form of Coulomb's law will only describe the magnitude of the electrostatic force between two electric charges. If direction is required, then the vector form is required as well.
Coulombs law: if two charges q1 and q2 are separated by a distance
r, the magnitude of the force between them is F = k |q1| |q2| / r^2; the force is repulsive if both charges are
negative or both are positive, and is attractive otherwise.
If the force is in Newtons, q1 and q2 in Coulombs, and r in meters,
then the constant k that appears in Coulombs law is equal to 9 x 10^9 SI units
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