Jones frictional plate electrostatic generator
date: label: date made
content: ca 1800
name: label: maker
content: W. & S. Jones
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: 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.
label: Description (Brief)
content: This portable plate machine comes from the shop of William and Samuel Jones, instrument makers in London. William Jones (1763-1831) founded the company in 1787 to make various scientific devices. His younger brother Samuel (d.1859) joined the firm four years later. The "K2A3" marking on the machine’s base was the Columbia University property number.
label: Description (Brief)
content: The single plate rubs against two pairs of leather pads set at top and bottom of the frame. The points on the brass arm gather the charge from the plate and transfer that charge to the brass ball that is mounted on top of a Leyden jar. A quadrant electrometer mounted on top indicates the amount of charge on the jar. A pith ball on a string hangs on the electrometer in front of a scale. Electrical charges of the same polarity repel and since the electrometer is charged along with the jar, the ball moves away from the jar. The higher the charge the further the ball moves up the scale. Leyden jars were discovered in 1742; a key step in modern electrical science. Then called condensers and now known as capacitors, these jars can store a charge but unlike batteries do not generate a current.
label: Location
content: Currently not on view
setName: label: See more items in
content: Work and Industry: Electricity
creditLine: label: Credit Line
content: from Columbia University, Department of Physics, thru Alvin P. Tramm
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.322954
label: accession number
content: 249200
label: catalog number
content: 322954
objectType: label: Object Name
content: Electrostatic machine
label: Object Name
content: electrostatic generator
physicalDescription: label: Measurements
content: overall: 17 in x 12 in x 12 in; 43.18 cm x 30.48 cm x 30.48 cm