This device serves to demonstrate the law that an attractive or repulsive force is present between point-like electrical charges, formulated in 1785 by the French physicist Charles Augustin Coulomb (1736 – 1806). The instrument measures the repulsive force between equal electric charges by means of the torsion that is produced in the wire that supports one of the two charges.

Its use is rather complex and delicate and is thus not suitable for teaching purposes in school. However, the instrument is of great historical importance, since it marks the transition between the qualitative study of electrical phenomena and their quantitative study based on experimental measurements and the formulation of mathematical laws.

Device on display.