Heat and Thermodynamics

2.4 Gas Thermometer

Liquid thermometers were later replaced by gas thermometers as their expansion is larger (≈ 20 times that of mercury thermometer) and thus the measurement is more accurate. The expansion of the container is small in comparison with the gas. Permanent gases can be obtained in pure state. Their expansion is uniform for equal changes of temperature at low and high temperatures. The upper limit of temperature measurement is much greater than liquid thermometer, limited to such temperature as the container can withstand.

Gas thermometers may be of two types: constant volume and constant pressure.

2.4.1 Constant Volume Hydrogen Thermometer

The bulb C (Fig. 2.1) containing hydrogen is 1m long and 3.6 cm in diameter and contains 1litre ...