Coulomb's law states that the electric force between two charges is directly proportional to the size of the charges and inversely proportional to the square of the distance between the two charges. The electric force between the two charges acts along a straight line between the two charges. Coulomb's law provides a numerical description of the electric force that exists between two charges.

Interactive exercise. Assistance may be required.

When solving numerical problems involving Coulomb's law and including the sign of the charge in the equation:

A positive answer indicates that the force between the two charges is a repulsion and the distance between the charges would increase.

A negative answer indicates that the force between the two charges is an attraction and the distance between the two charges would decrease.