Rousseau Ramsden-type frictional plate electrostatic machine

Rousseau Ramsden-type frictional plate electrostatic machine

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Description (Brief)
People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
In the latter 1700s electrical researchers adopted improved electrostatic machines that replaced earlier glass cylinders with a flat glass plate. This increased the machines’ efficiency by passing the glass plate between leather rubbing pads that increased the contact area. Experience with plate machines brought many design variations with sizes ranging from small table-top units for laboratory use to large cabinets that powered early x-ray machines.
This is a single-disc generator for table-top use that follows a design by Jesse Ramsden (1735-1800). The operator turns the crank which rotates the glass plate. The plate rubs against the treated leather pads generating the static charge that is stored in the brass frame, called the prime conductor. A quadrant electrometer mounted on top of the prime conductor indicates how much charge is on the conductor. A pith ball on a string hangs on the electrometer in front of a scale. Electrical charges of the same polarity repel and since the electrometer is charged along with the prime conductor, the ball moves away from the conductor. The higher the charge the further the ball moves up the scale.
The generator is marked "E. Rousseau Et Ses Fils, Paris." Emil Rousseau (1812-1886) was a French chemist who founded a company to make chemical supplies and apparatus. Although referred to as a Ramsden machine, the unit has no direct link to the early developer of plate machines. According to historian Willem Hackmann, Jesse Ramsden’s name became a generic term in France for plate machines. This machine was restored in late 1958. Aside from being cleaned and polished a missing foot and the missing electrometer were replaced. A Rousseau machine very much like this one can be seen in an image of Thomas Jefferson made by artist Cornelius Tiebout about 1801.
Location
Currently not on view
Object Name
Electrostatic machine
electrostatic generator
date made
ca. 1850
ca 1850
Measurements
overall: 24 in x 19 in x 32 in; 60.96 cm x 48.26 cm x 81.28 cm
ID Number
EM.315899
accession number
222953
catalog number
315899
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Work and Industry: Electricity
Data Source
National Museum of American History
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