Contributions from the Physical Laboratory of the University of Michigan Volume 1-5 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...Ann. d. Phys., 17, p. 960, 1905. 2 Hyde, Jour. Franklin Inst., 170, p. 32, 1910. Attempts to fit this relation to experimental data for various spectral energy curves, assuming E to be some simple function of X, as, for example, E = &X, have, however, not been entirely successful.1 Whether the difficulty lies in the choice of the function EK, or in a variation of selectivity with temperature, remains to be determined, but Hyde2 has demonstrated by means of a simple criterion obtained directly from equation (i) that such variations probably do exist in the case of tungsten filaments. Bidwell3 has found evidence of a similar effect by direct measurements upon a mass of nickel whose temperature could be observed and controlled over a considerable range. One of the objects of the present investigation is to determine whether or not the osmium filament exhibits a temperature variation of selectivity. Osmium was chosen for study in this connection because, in the first place, its selectivity is probably higher than that of most other metals so that the effects sought will be most easily measurable, and secondly, its characteristics have not been very fully described so that any data obtained from it will be of interest. The lamps, which were obtained through the courtesy of Dr. Hyde, of the Nela Research Laboratory, consume normally about 39 watts at 42 volts, giving approximately.55 candle power per watt. The filaments consist of two separate loops in series, each anchored to the glass bulb at the outer end. The investigation consists of (1) a study of the behavior of three osmium lamps under various operating conditions, with a test for selectivity; (2) a qualitative study, by comparison with carbon lamps, of the characteristic radiation from these filament...