Abstract
MESSRS. ROSA AND BABCOCK, at the Bureau of Standards, found that manganin wire resistances used in resistance boxes varied according to the time of the year; for instance, in summer they were 0-015 Percent, to 0-025 Percent higher in value than they were in the same temperature in winter. These experimenters explain this periodic variation by the fact that with increased relative air humidity the shellac, especially that between the metal tube and the wire, swells; the base on which the wire is wound consequently increases in diameter, and the forces thereby created cause the resistance wire to expand elastically. With decreasing humidity the shellac gives off moisture and shrinks, the pressure on the wire is relaxed, and the resistance decreases.
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The Influence of Humidity on Resistances . Nature 78, 583 (1908). https://doi.org/10.1038/078583a0
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DOI: https://doi.org/10.1038/078583a0