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Last updated date: 02nd Dec 2023
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MVSAT Dec 2023

Which thermometer is used for measuring the temperature near absolute zero?
A) Thermoelectric thermometer
B) Radiation thermometer
C) Magnetic thermometer
D) Resistance thermometer

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Hint: The minimum possible temperature which is coldest of all and there is no heat energy present. This temperature is known as Absolute zero. It requires thermometers which measure very low temperature with high precision.

Complete step by step answer:
Absolute Zero can be defined as the temperature in the thermometer which is lowest of all. It is the minimum possible temperature in the thermometer and there is no heat present in the system.
Thermoelectric thermometers are those which consist of two thermocouples which are connected in series with a potentiometer and a constant-temperature bath. One couple, called the reference junction, is placed in a constant-temperature bath, while the other is used as the measuring junction. The measuring junction can be made physically very small in order to have practically a negligible thermal time constant. These cannot measure very low temperatures, so they cannot be used for measuring absolute zero temperatures as there is heat energy present.
Radiation Thermometers are thermometers which do not need to make contact with the body or an object for measuring the temperature. These measure temperature by using their emitted thermal radiations. These cannot measure the internal temperature of the body. So, these cannot be used for measuring temperature near absolute zero.
The magnetic thermometer uses the principle of adiabatic demagnetization of magnetic material. So, they can measure very low temperatures with high precision. So, this thermometer is most suitable for measuring temperature near absolute zero.
Hence, option (C) is the correct answer.

Note: The magnetic thermometer uses the Curie’s law which states “magnetic susceptibility of dipole moments is inversely proportional to absolute temperature.” The magnetic moments in the thermometric material may be of either electronic or nuclear origin.