variable inductance
Date: ca. 1915-1925
Inventory Number: RS0556
Classification: Tuning Coil
Subject:
Maker: General Radio Company (1915-present)
User: Cruft Laboratory, Harvard University (founded 1914)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
10 x 13.5 x 13.5 cm (3 15/16 x 5 5/16 x 5 5/16 in.)
Material:
Description:
Coil encased in a cylindrical brass body with dark discoidal top panel. Large dial with 2 electrical connectors on top.
In Collection(s)
Signedon dial: GENERAL RADIO CO. / CAMBRIDGE, MA
Inscribedon base in black: 18
stamped on base: 124 B
stamped on base: 124 B
FunctionThe frequency of transmission or reception of a radio circuit is inversely proportional to the square root of both its capacitance and inductance. Tuning coils are one of the methods used to alter a circuit's frequency, by altering the circuit's inductance.
In this particular case, the inductance of the coil (which would be part of the circuit) is changed by turning the knob, which makes one of the points of electric contact move along the coil wires, changing the effective size of the coil. Less loops and wire between the two electric contacts means a smaller inductance.
In this particular case, the inductance of the coil (which would be part of the circuit) is changed by turning the knob, which makes one of the points of electric contact move along the coil wires, changing the effective size of the coil. Less loops and wire between the two electric contacts means a smaller inductance.
Historical AttributesThe triangle indicates its instructional use at the Physics Department, Harvard University.
ProvenanceFrom the Cruft Laboratory, Harvard University.