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Carre frictional electrostatic generator

Carre frictional electrostatic generator

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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 electrostatic machine was designed and made about 1875 in Paris by Ferdinand Carré (1824-1900). An unusual hybrid design, this machine operates by both friction and electrical induction. The lower glass plate rubs against a pair of leather pads, generating an electrostatic charge. The crank rotates both plates and the charged glass plate induces a charge on the upper plate which is made of ebonite.
Electrostatic induction occurs when a charged body (the glass disc, in this case) causes another body (the ebonite disc) that is close but not touching to become charged. The glass disc is said to influence the ebonite disc and some so-called influence machines, work solely on that principle. Points on the brass arms pick the charge off the ebonite plate and conduct the charge to the metal cylinder on top of the machine, called the prime conductor. The ring under the prime conductor can hold a Leyden jar or other experimental component. According to Adolphe Ganot, who described "Carré's dialectrical machine" in 1879, the unit “is not very much affected by moisture, and it yields a large supply of electricity.”
Location
Currently not on view
Object Name
electrostatic generator
Electrostatic Machine
maker
Carre, Francois
Measurements
overall: 35 in x 17 in x 34 in; 88.9 cm x 43.18 cm x 86.36 cm
ID Number
EM.322997
catalog number
322997
accession number
249201
Credit Line
from Wabash College, Physics Dept., thru Robert L. Henry
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Work and Industry: Electricity
Data Source
National Museum of American History
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