British philosopher, theologian, and scientist Joseph Priestley (1733-1804) suggested that the force caused by static electricity might depend on distance the same way gravity does. Using Priestley’s idea, the French physicist Charles Coulomb (1736-1806) made quantitative measurements of the force of attraction and repulsion between charged objects using an apparatus shown in the accompanying illustration. He found that the force depended on the charge of the two objects and the distance between them. The relationship he found is called Coulomb’s Law and the unit of measurement of charge as the coulomb (C).