Wimshurst-type influence machine

Wimshurst-type influence 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.
Many early electrostatic machines generated a charge by friction. In the later 19th century several designs were introduced based on induction. Electrostatic induction occurs when one charged body (such as a glass disc) causes another body (another disc) that is close but not touching to become charged. The first glass disc is said to influence the second disc so these generators came to be called influence machines.
This influence machine, made in New York City by the firm Hall & Harbeson, shows the design of Wilhelm Holtz (1836-1913) of Germany. Around 1865 Holtz’ new machine featured a fixed plate with two holes called windows, both of which had two contacts called sectors. The sectors were made of paper and on this machine each has a separate saw-toothed edge made of metal. The slightly smaller rotating plate is turned by the user with a crank and spins close to the fixed plate, charging as it spins. Two brass combs mounted on the glass stands gather the charge that is then conducted to a Leyden jar. When using the Holtz design one needed to prime the machine by putting a charge on one of the sectors and then connecting the electrodes to begin building up the charge. The brass bar attached to the axle is called the neutralizer bar and prevents the charging action from reversing at the wrong time and discharging the machine.
Location
Currently not on view
Object Name
influence machine
electrostatic generator
Other Terms
electrostatic generator; Electrostatic Devices
date made
ca. 1890
ca 1890
Measurements
overall: 31 1/2 in x 24 1/4 in x 16 in; 80.01 cm x 61.595 cm x 40.64 cm
ID Number
EM.330656
catalog number
330656
accession number
299612
Credit Line
from Princeton University, Department of Physics, thru Frank Shoemaker
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Work and Industry: Electricity
Science & Mathematics
Data Source
National Museum of American History
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