18th Century Electrostatic Machine

Description
This machine was used to generate static-electric charges for scientific experiments and demonstrations. Anyone who has walked across a carpet and been shocked when touching a door knob has conducted an experiment in generating static charges. This machine generates electricity the same way--by friction.
Elaborate experiments could be performed with electrostatic machines. The experimenter operated the machine by turning a crank and rotating the glass sphere. That generated an electrical charge by rubbing against a pad of cloth or leather. The charge would be collected by a comb of brass points and stored in a brass “prime conductor”–-typically a hollow cylinder. Neither the comb nor the prime conductor survive for this unit. Experiments investigating the electrical field surrounding the prime conductor or a charged body could be performed by bringing a material of interest into close proximity. If one was grounded, touching the prime conductor immediately discharged the machine, unlike the steady flow of current obtained from a battery. Prior to the invention of batteries and magneto generators, these machines constituted the primary means of generating electricity for experimental use.
Static-electric machines were first developed in Europe in the early 1700s, but this example was made and used in the US. Machines made in Europe tended toward a horizontal orientation, while American machines were mounted more vertically. This hand-made machine probably dates from the 1750s or 60s. The maker of this machine is unknown but research by museum staff indicates a design influenced by Benjamin Franklin. Aside from its similarity to other Franklin machines, an 1870s label from the donor (Princeton University) and oral tradition at that school both associate this machine with Franklin, though it is believed unlikely that Franklin himself used this particular machine.
Object Name
electrostatic machine
electrostatic generator
date made
ca. 1750
Physical Description
wood (overall material)
glass (globe material)
fiber (part material)
rubber (part material)
cloth (part material)
metal (part material)
Measurements
overall: 60 1/2 in x 30 in x 27 1/2 in; 153.67 cm x 76.2 cm x 69.85 cm
ID Number
EM*325513
catalog number
325513
accession number
2008.0088
subject
Energy & Power
Science & Mathematics
Science & Scientific Instruments
Artifact Walls exhibit
See more items in
Work and Industry: Electricity
Artifact Walls exhibit
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
from Princeton University, Department of Physics

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