Explain the working of constant volume gas thermometer.

Constant Volume Gas Thermometer:

A constant volume gas thermometer ususally consists of a bulb filled with a fixed amount of a dilute gas which is attached to a mercury manometer. The manometer is used to measure variation in pressure. This thermometer works on the principle of Law of Gay-Lussac

Explanation:

A constant volume gas thermometer is composed of a bulb filled with a fixed amount of a dilute gas that is attached to a mercury manometer. A manometer is a device used to measure pressure.

The mercury manometer has a column partially filled with mercury that is connected to a flexible tube that has another partially filled column of mercury, called a reservoir, attached to the other end. The height of the mercury in the first column is set to a reference point or pressure P that it must stay at, while the mercury in the reservoir is allowed to move up and down in relation to a scale or ruler.

From the Law of Gay-Lussac, we know that when the temperature of an ideal gas increases, that there is a corresponding increase in pressure. Conversely, when the temperature decreases, so does the pressure. Constant volume gas thermometers operate on the same principle, with the restrictions that the gas is at low pressure and the temperature of it is well above that of liquefaction.