Which of the following is chosen as a standard thermometric substance ?

Which of the following is chosen as a standard thermometric substance ?

a. Gas
b. Thermocouple
c. Electric resistance
d. Mercury

Correct Answer : a. Gas

Explanation :

When the temperature of a system is measured simultaneously with all the above thermometers which are in options, then it is found that there are considerable variation among the readings. But with experiments, it is found that the minimum variation is observed among the gas thermometers. Therefore gas is chosen as a standard thermometric substance.