Menu Close

Foucault Switch (Carpentier)


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.

Accession Number:

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


This artifact was part of a collection of electrical instruments (mostly brass electrometers and ballistic galvanometers) gathered by University of Toronto Professor of Physics Martin J.G. Lee (d. 2009). The collection was likely acquired from Dr. Lee’s office c. 2010 or 2011.

Additional Information and References:

Pierre Adolphe Daguin. Traité élémentaire de physique théorique et expérimentale avec les applications à la météorologie et aux arts industriels. Ed. 4. Paris: Delgrave, 1878.

Historical Notes: