How do physicists calculate the force between two charged objects?

For two stationary point charges, the electric force is given by Coulomb’s law. The force increases when either charge gets larger and decreases with the square of the distance between them, so doubling the distance makes the force one-quarter as strong. This law was established experimentally by Charles-Augustin de Coulomb in the 1780s using a torsion balance. It explains why static electricity, ion attraction, and many atomic-scale interactions behave the way they do. In quantum physics, the same basic electromagnetic interaction is described more fully by quantum electrodynamics, but Coulomb’s law remains a powerful approximation.