Inventor: Johann Gottlieb Friedrich von Bohnenberger, b.1765 - d.1831. German physicist and mathematician.

Date: 1st quarter 19th century

Description

A glass bell-jar closed by a sealing wax-varnished cap is mounted on a brass base with three feet. A brass rod, inserted in the cap, holds a golden leaf placed between two metallic plates. The plates are connected to the opposite poles of two Zamboni dry batteries. Outside the bell-jar, the rod terminates in a brass sphere, to which the electricity to be measured was communicated. The golden leaf was thus electrified and it was attracted by the plate charged with electricity of opposite sign. The deviation of the leaf thus also indicated the sign of the applied electricity. The position of the two batteries can be modified thanks to two metallic rods.

T. G. B. Behrens  designed in 1806 an electroscope with a golden leaf suspended between two voltaic batteries and J.G.F. Bohnenberger, in 1814, substituted the voltaic batteries with dry ones, thus obtaining a more sensitive instrument.

Materials and techniques: brass/glass/wood/sealing wax

Dimensions: height 33 cm, diameter 16 cm

Keywords: electricity, electrostatics

University of Padua, Museum of the History of Physics

Cat. Number: 242

Exhibitions

• "Bagliori nel vuoto. Dall'uovo elettrico ai raggi X: elettricità e pneumatica dal Seicento ad oggi", Padua, Botanical garden, 1 February-30 June 2004

Bibliography

• Adolphe Ganot, Traité élémentaire de physique expérimentale et appliquée et de météorologie, 14 ed., Paris, 1870
• Jules Jamin, Cours de physique de l’Ecole Polytechnique, 3 vols., Paris, 1858-1866