Foucault Switch


Accession Number:


This switch consists of a brass apparatus mounted upon a wooden base. The switch itself is composed of several parts including a pair of solenoids, an arm attached to vertical rod and a spherical weight, a metal tube containing oil and a glass tube containing mercury. The arm is positioned so that it can come in contact with the mercury and the solenoids. The arm is also attached to a sponge that is submerged in the oil.

The mercury has since been removed from the device.

Alternative Name:

Primary Materials: Wood, Brass


On the left end of the base there is a engraved metal plate with reads: “Ateliers Ruhmkorff/J Carpenter Ing Const. 1601Paris”.

Dimensions (cm): Height = 28, Length = 29, Width = 21


Automates the periodic interruption of an electrical circuit at relatively high speeds.


Good: one electrical terminal is detached as the result of a broken screw (see image 7.)

Associated Instruments:


Ateliers Ruhmkorff/Jules Carpenter, Paris

Date of Manufacture: c. 1880


One among a collection of instruments gathered by Dr. Martin Lee at the Department of Physics.

Historical Notes:

Daguin, Pierre Adolphe. 1878. Traite? e?le?mentaire de physique the?orique et expe?rimentale avec les applications a? la me?te?orologie et aux arts industriels. Paris: Delgrave.

There is also a Foucault switch in Physics Museum of Sardinia: