Coil Inserts Research Articles

IV. The influence of stress and strain on the physical properties of matter. Part I. Moduli of elasticity— continued . Relations between moduli of elasticity, thermal capacity, and other physical constants

The thermal capacity of each of the wires already used for the experiments on moduli of elasticity and electrical conductivity described in Parts I and II of this paper was determined in the following manner:—The wires, which had been previously well annealed, were wound round a steel rod and so made into coils of length about 2 inches, inner diameter 3/4 inch, and outer diameter 1 3/4 inches, the rod was then withdrawn and the coil inserted into a thin brass envelope. The envelope consisted of a hollow cylinder 2 inches in length and 2 inches in diameter, terminated at both ends by a truncated cone. One of the conical ends was closed and could be unscrewed so as to receive the coil of wire, and was, after the insertion of the coil, screwed on again. At the other extremity of the envelope was an aperture 3/4 inch in diameter, through which a thermometer could be inserted, so that its bulb would lie along the axis and in the centre of the coil of wire. The brass envelope and the contained coil were heated in an air-chamber consisting of two concentric copper cylinders of equal length connected at their two ends, so as to enclose between them a layer of water £ inch thick. The length of the air-chamber thus formed was 14 inches, and the inner diameter 2 1/4 inches, so that the envelope could freely slide through the chamber. The two ends of the air-chamber, which was placed in a horizontal position, were closed by corks, through the centre of one of which passed a thermometer, and through a very small hole in the centre of the other was drawn a fine but strong thread attached with one extremity to the envelope, and with the other wound round a little piece of wood which prevented the thread from being dragged through the hole when the former was drawn tight. The envelope and contained wire were heated before immersion in the water of the calorimeter in one set of experiments to about 60° C., and in another set to about 100° C. The envelope served a double purpose, as it not only enabled compensation to be made for loss of heat during the transference of the wire from the air-chamber to the calorimeter, but also was of use in distributing the heat uniformly throughout the coil. Preliminary observations were made for the purpose of ascertaining the rise of temperature which would be caused by immersing the heated envelope only in the water of the calorimeter.