On Coulomb’s Law
Coulomb’s law states that the magnitude of the electrostatic force of
attraction between two point charges is directly proportional to the
product of the magnitudes of charges and inversely proportional to the
square of the distance between them. The force is along the straight
line joining them.
If the two charges have the same sign, the electrostatic force between
them is repulsive; if they have different signs, the force between them
is attractive.