Globe-type Electrostatic Machine
date: label: date made
content: ca 1750
notes: label: Description (Brief)
content: 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.
label: Description (Brief)
content: This incomplete machine dates from about 1750 and appears to be Benjamin Franklin’s design. In the late 1740s, Franklin began investigating electricity with instruments supplied by friends in Britain. Scientific instruments of all types were in short supply in colonial America so Franklin supplemented his imported equipment with items of his own design. Early electrostatic machines generated a charge by spinning a globe against a pad. The charge could then be used directly in experiments or transferred from the globe to a Leyden jar. The hollow glass globe on this machine rubs against a leather pad seasoned with a specially formulated grease. The charge collector assembly, missing from this machine, consisted of brass pins that rode against the glass and carried the charge to a brass ball set on an insulating glass rod. Princeton University donated this machine in the 1960s and kept a second machine for display there. The exact origin of the two generators is uncertain but an oral tradition at Princeton associates both machines with Franklin.
topic: label: classified
content: Science & Scientific Instruments
setName: label: See more items in
content: Work and Industry: Electricity
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content: Energy & Power
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content: Science & Mathematics
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content: Artifact Walls exhibit
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content: Electrostatic Machines
label: Exhibition
content: The Electric Dr. Franklin
label: Exhibition Location
content: National Museum of American History
creditLine: label: Credit Line
content: from Princeton University, Department of Physics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.325513
label: catalog number
content: 325513
label: accession number
content: 2008.0088
objectType: label: Object Name
content: globe-type frictional electrostatic machine
label: Object Name
content: electrostatic generator
label: Other Terms
content: globe-type frictional electrostatic machine; Electrostatic Devices
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: glass (globe material)
label: Physical Description
content: fiber (part material)
label: Physical Description
content: rubber (part material)
label: Physical Description
content: cloth (part material)
label: Physical Description
content: metal (part material)
label: Measurements
content: overall: 60 1/2 in x 30 in x 27 1/2 in; 153.67 cm x 76.2 cm x 69.85 cm