Cavendish experiment

Coulomb's law

Level 0 (green)- this is basic material that you have probably encountered already, although the approach may be slightly different. No prior knowledge is assumed.

Coulomb's experiment

Charles Augustin de Coulomb did a careful series of experiments in the 1780's, in which he measured the dependence of the electrostatic repulsion between two charged spheres as a function of distance between the spheres using a sensitive torsion balance.

There is a YouTube video of a working Coulomb torsion balance.

In the experiment shown the spheres are charged, the balance is set to a specific force and the spheres move until their repulsion equals this force. In this way Coulomb showed that the force depended inversely on the square of the distance between the spheres, like Newton's gravitational force.

Coulomb also did experiments in which an uncharged sphere is put into contact with one of the charged spheres. They then share the charge between them so that when the unch Charles coulombs law!