Previous Year Question
Which one of the following thermometers is known as pyrometer?
Thermo-electric thermometers
Radiation thermometers
Gas thermometers
Liquid thermometers
Correct Answer: B
Detailed Solution
A pyrometer is a temperature-measuring instrument particularly useful for measuring very high temperatures. A radiation pyrometer determines temperature by detecting the thermal radiation emitted by an object, without requiring direct physical contact with it.
The electromagnetic radiation emitted by a hot object depends on its temperature. As temperature increases, both the intensity and spectral distribution of the emitted radiation change. A radiation pyrometer uses this radiation to determine the object's temperature.
A major advantage is non-contact measurement. Therefore, it is useful for measuring the temperature of molten metals, furnaces and other very hot or inaccessible objects for which direct contact with an ordinary thermometer may be difficult or unsafe.
A Thermo-electric thermometer generally works on the thermoelectric effect using a thermocouple. A Gas thermometer uses changes in the pressure or volume of a gas with temperature, whereas a Liquid thermometer works on the thermal expansion of a liquid.