Explanation:- If volume of a gas is maintained at constant and If a certain volume of inert gas is enclosed in a bulb, capillary and bourdon tube, the most of the gas in the bulb, then the pressure increases with increase in temperature and that pressure is indicated by the bourdon tube may be calibrated in terms of the temperature of the bulb
In other words
Working of Gas thermometer is depend upon ideal gas law which state that the volume of the gas increases with increase in temperature if pressure maintained constant.
Name of the gases used in Gas filled thermometers.
1. Nitrogen 2. Helium 3. Inert Gas