Sweating in human body
Sweating in human body is an example of Zeroth Law of Thermodynamics. If the atmospheric humidity is low,
sweat evaporates easily. The heat energy needed to evaporate this sweat comes from our bodies., hence sweat evaporation cools
the body.
If heat is added to a closed system, T will increase. Conversely, if heat is extracted from a closed system, T will decrease.
“Two systems individually in thermal equilibrium with a third system, are in thermal equilibrium with each other.”
The zeroth law of thermodynamics states that if two systems, A and B, are in thermal equilibrium with a third system, C, then A and B are in thermal equilibrium with each other. It is analogous to the transitive property in math (if A = C and B = C, then A = B). One can apply the zeroth law of thermodynamics to compare the temperatures of multiple objects. The zeroth law sets up the idea of temperature as an indicator of thermal equilibrium.
Another way of stating the zeroth law is that every object has a certain temperature, and when two objects are in thermal equilibrium, their temperatures are equal. It is called the “zeroth” law because it came to light after the first and second laws of thermodynamics had already been established and named, but was considered more fundamental and thus was given a lower number – zero.