Globe-type Electrostatic Machine

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.
This portable generating machine from around 1760 comes with an experimental kit of accessories. 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 hand-cranked ball of sulfur on this machine rubbed against a leather pad. The pins on the brass rod set close to the ball transferred the charge from the ball to the rod, called a prime conductor. Suspended from a frame by insulating silk threads, the charged prime conductor allowed a researcher to show electrical properties like attraction, repulsion, and strength of charge. Accessories include pith balls, a chime of bells, a Leyden jar, and assorted plates, hooks and dischargers.
This machine is especially interesting as we have an original design drawing in the collection showing this type of machine--catalog #1988.0621.01.
Location
Currently not on view
Object Name
generator, electrostatic
frictional globe machine
electrostatic generator
date made
ca 1760
Physical Description
wood (overall material)
glass (overall material)
brass (overall material)
silk (overall material)
metal (overall material)
sulfur (overall material)
leather (overall material)
Measurements
overall: 57 cm x 27.5 cm x 67 cm; 22 7/16 in x 10 13/16 in x 26 3/8 in
ID Number
1983.0190.01
accession number
1983.0190
catalog number
1983.0190.01
See more items in
Work and Industry: Electricity
Science & Mathematics
Electrostatic Machines
Data Source
National Museum of American History, Kenneth E. Behring Center

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