Earth Inductor or Palmieri Apparatus
name: label: maker
content: Max Kohl
notes: label: Description
content: Michael Faraday found that the magnetic force of the earth could induce electrical currents in metallic bodies in motion. Building on this idea, Charles Delezenne in France introduced an earth inductor in 1844.
label: Description
content: The inscriptions on this instrument read "MAX KOHL Werkstätten für Prazisions Mechanick CHEMNITZ I.S." and "CENTRAL SCIENTIFIC CO. LABORATORY APPARATUS CHICAGO U.S.A." Kohl described it as an "Earth Inductor after Palmieri...with round frame 300 mm diameter, with 100 turns of 1 mm thick wire, with commutator." Luigi Palmieri was a physicist in Naples who, in the 1840s, developed an earth inductor with elliptical ring that rotated around its longer axis. The Palmieri apparatus with a circular ring, as in this example, seems to have originated in the 1860s.
label: Description
content: Max Kohl was in business as a scientific instrument maker from 1876 to 1937. The Central Scientific Co. was established in 1900. This example belonged to Trinity College in Hartford, Conn., and came to the Smithsonian in 1981.
label: Description
content: Ref: Max Kohl, <i>Physical Apparatus</i> (Chemnitz, 1926), p. 974.
label: Location
content: Currently not on view
place: label: Place Made
content: Germany: Saxony, Chemnitz
topic: label: Subject
content: Science & Scientific Instruments
label: Subject
content: Science & Scientific Instruments
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Science & Mathematics
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content: Measuring & Mapping
creditLine: label: Credit Line
content: Trinity College, Department of Physics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1981.0743.04
label: accession number
content: 1981.0743
label: catalog number
content: 1981.0743.04
objectType: label: Object Name
content: earth inductor or Palmieri apparatus
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: metal (part material)
label: Measurements
content: overall: 15 3/4 in; 40.005 cm
label: Measurements
content: overall: 17 in x 19 1/4 in x 11 3/4 in; 43.18 cm x 48.895 cm x 29.845 cm