resistance standard
Date: 1893-1910
Inventory Number: 0512d
Classification: Resistance Standard
Subject:
Maker: Queen & Company (1893 - 1912)
User: Department of Physics, Harvard University (founded 1884)
Cultural Region:
Place of Origin:
Dimensions:
10.2 × 15.4 × 8 cm (4 × 6 1/16 × 3 1/8 in.)
box: 12.7 × 33.3 × 18.1 cm (5 × 13 1/8 × 7 1/8 in.)
Description:
[On the right] A coil of manganin wire (an alloy made of 86% copper, 12% manganese, and 2% nickel, first developed by Edward Weston in 1892) wound on a tube and covered in paraffin. This part of the instrument is protected by a nickel-plated copper removable cylinder. Two terminals that would be dipped in mercury, connected to the manganin coil, are attached like the rest of the instrument on a wooden base.
Signedon instrument: QUEEN & CO. / PHILA.
Inscribedon instrument: FOUR OHMS at 19.6 °C
on instrument: RP3 [SPACE] 5
on base, stamped: 95
on instrument: RP3 [SPACE] 5
on base, stamped: 95
FunctionA standard resistance is not to measure the resistance of an electric conductor but rather to compare such a conductor to a temperature-fixed resistance. In other words, such a device is used to determine the value of an unknown current. To do so, a current in the conductor would pass through mercury (for the older type of standard resistance), into which the two leads from the resistor dip. The manganin wire on this instrument was baked before being dipped into paraffin so that all moisture is removed and to improve the insulation over the wire.
Curatorial RemarksWas first incorrectly catalogued as 1997-1-0228d, so slide will show it with that number.
0512a-d stored in blue-board tray together. SMS 1/10/2019
0512a-d stored in blue-board tray together. SMS 1/10/2019
ProvenanceFrom the Department of Physics, Lyman Laboratory, Harvard University.