C.A.Coulomb was a french military engineer retired owing to a delicate health.
After have made important experiments on friction in shipyard of Rochefort became member of the Sciences Accademie of France.
In 1791 discovered that the force of electric attraction between bodies varies inversely as the square of the distance between them.
To measure out the forces of the electric field Coulomb used an instrument of his invention: the torsion balance (see figure) with two little spheres in pith of elder.