The Laws of Thermodynamics are four parts:
Zeroth Law of Thermodynamics:
Thermal Equilibrium
The zeroth law of thermodynamics states that when two bodies have equality of temperature with a third body, they in turn have equality of temperature with each other. This seems obvious to us because we are so familiar with this experiment. Because the principle is not derivable from other laws, and because it precedes the first and second laws of thermodynamics in the logical presentation of thermodynamics, it is called the zeroth law of thermodynamics.
This law is really the basis of temperature measurement. Every time a body has equality of temperature with the thermometer, we can say that the body has the temperature we read on the thermometer. The problem remains of how to relate temperatures that we might read on different mercury thermometers or obtain from different temperature-measuring devices, such as thermocouples and resistance thermometers. This observation suggests the need for a standard scale for temperature measurements.
First Law of Thermodynamics:
The first law of thermodynamics states that energy cannot be created or destroyed during a process (such as compression and delivery of a gas), although it may change from one form of energy to another. In other words, whenever a quantity of one kind of energy disappears, an exactly equivalent total of other kinds of energy must be produced. It is also known as Law of Conservation of Energy.
Second Law of Thermodynamics:
- Heat cannot, of itself, pass from a colder to a hotter body.
- Heat can be made to go from a body at lower temperature to one at higher temperature
only if external work is done. - The available energy of the isolated system decreases in all real processes.
- Heat or energy (or water), of itself, will flow only downhill.
Third Law of Thermodynamics:
The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.
« Back to Glossary Index