Open AccessThe heating effect of the currents in precise measurements of electrical resistance
Author(s) -
Richard Glazebrook,
W. R. Bousfield,
Frank E. Smith
Publication year - 1911
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1911.0068
Subject(s) - current (fluid) , materials science , radius , manganin , alloy , copper , electrical resistance and conductance , metallurgy , chemistry , composite material , electrical engineering , thermodynamics , physics , acceleration , computer security , classical mechanics , computer science , engineering
In a paper on the specific heat of water, one of us describes an experiment in which the passage of a current of 4·4 ampères through an oil-cooled manganin resistance of 1·2-mm. wire produced an increase in the resistance corresponding to an increase of temperature of 60° C. As the cooling surface of the resistance was 16 sq. cm. per watt, such a large increase of temperature was thought to be improbable, and the change of resistance was attributed to some other cause. However, the effect of the passage of the current was similar to that resulting on raising the temperature, and, because of this, it was proposed to call the change athermoid effect. With platinum wires similar results were obtained, the increase of resistance being nearly proportional to the square of the current and inversely proportional to the radius of the wire. The change of resistance with varying current was investigated by Dr. E. H. Griffiths in 1893. Using a fine platinum wire, he found the increase of resistance to be proportional to the square of the applied voltage. With regard to this increase, Dr. Griffiths remarks:—“It seemed absolutely immaterial whether the current was on for only a few seconds or indefinitely.” Previous experiments on an alloy of copper, manganese, and nickel had shown that the resistance of the alloy changed appreciably in the course of one and a-half hours when a current of ½ ampère was passed through it, and Dr. Griffiths states that the rise appeared to be a function of the current rather than of the time. If, in Dr. Griffiths’ determination of the mechanical equivalent of heat, he had neglected the rise of resistance of the wire with increasing current, an error of about 1 part in 60 would have been introduced.