Conductivity of Gases
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
P-250
2025-11-22
42
Gases are extremely poor conductors of heat, the conductivity of air being only 1/2000 of that of copper. Double windows prevent air currents that would carry away the heat, and on account of the low conductivity of air are a protection from the cold. The fur of animals is an efficient protection because of the layer of air that is connected with it. The protection in both these cases consists in preventing the heat from within from escaping. Practical use of air spaces to prevent the transfer of heat is made in the double walls of ice houses and refrigerators, for keeping the heat out, and in fireless cookers for keeping the heat in.
Still better results are obtained by exhausting the air from between the double walls, as in the thermos bottle, in which either hot or cold liquids can be kept without much change of temperature for some hours.
FIG. 1.-Thermos Bottle
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