Publish On: 2019-04-25

Andy More

Total Post: 752

Question: Describe gas thermometers

Reply On: 2013-10-19

lala singh

Total Post: 22

ANS: Describe gas thermometers

The gases most suitable for use in a gas thermometer are hydrogen, nitrogen and helium; for oxygen and, to some extent, even air attacks the mercury used in the tube to measure pressure etc.

Of the two, the constant volume type of thermometer is generally preferred. For, at constant pressure, there is a fairly large expansion of the gas with rise of temperature and, with the gas occupying more and more of volume, it becomes difficult to maintain the whole of this volume at a uniform temperature. So that, it gives rise to a problem somewhat similar to that of the emergent column of a mercury thermometer. In the constant volume type of thermometer there is no such difficulty, or at any rate, not so serious, because the volume of the gas, maintained constant, can be made quite small. Another point in its favour is that the specific heat of a gas at constant volume being smaller than at constant pressure, it absorbs less heat from the system with which it is placed in contact than a constant pressure type of thermometer would.

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