Before first law of thermodynamics there is zeroth law of th

Before first law of thermodynamics, there is zeroth law of thermodynamics. The thermometer works on the principle of zeroth law of thermodynamics. Can you explain what is a zeroth law of thermodynamics?

Solution

Zeroth law states that Objects into contact will reach a thermal equilibrium (and heat transfers from hotter to colder), this means one can use a device that can measure this difference of this quantity as follows:

We have a device (called a thermometer) which has an indication. When the \"thermometer device\" comes into contact with another object, 0th law states that they wil reach thermal equilibrium . Then the indication of the device will change to reflect the difference of this quantity that changed or transfered and refered to as temperature .

One such device is the thermometer based on mercury (which is used as the indicator due to its special heat expansion factor).