Laws of thermodynamics | Statement | Formula
The basic principles of thermodynamics were expressed originally in three laws. But it was decided after that, that a more basic law had been ignored. It had seemed so clear it didn't have to be clearly mentioned. Scientists agreed that this most basic law had to be included to form a full collection of laws. The name of this law is the zeroth law of thermodynamics. Now let us understand all the laws in brief one by one below.
Define laws of thermodynamics:
- Zeroth Law of thermodynamics
This law states that when the two systems are in thermal equilibrium with a third system then they are in thermal equilibrium with each other.
- First Law of Thermodynamics
The first thermodynamic law is a variant of the energy conservation law, adapted for thermodynamic systems.
This law states that the total energy of an isolated system is constant, energy can be transformed from one form to another, but can be neither created nor destroyed.
For example, the energy due to heat supplied Q must be balanced by the external work done W plus the gain in internal energy E due to rise in temperature.
Q = W + E
- Second Law of Thermodynamics
According to Clausius, this law states that heat energy can not be transferred from body at a lower temperature to a body at a higher temperature without the addition of energy.
According to Kelvin-Planck, this law states that the design of an engine running on a cyclic cycle, whose sole function is to transform heat energy into work, is impossible.
This law states that when the two systems are in thermal equilibrium with a third system then they are in thermal equilibrium with each other.
The first thermodynamic law is a variant of the energy conservation law, adapted for thermodynamic systems.
This law states that the total energy of an isolated system is constant, energy can be transformed from one form to another, but can be neither created nor destroyed.
For example, the energy due to heat supplied Q must be balanced by the external work done W plus the gain in internal energy E due to rise in temperature.
Q = W + E
According to Clausius, this law states that heat energy can not be transferred from body at a lower temperature to a body at a higher temperature without the addition of energy.
Occasionally, the second law of thermodynamics is called a law of energy depletion.
Example: This is why we cost money to run an air conditioner.
The second law is applicable to a wide variety of processes such as reversible and irreversible.
- Third Law of Thermodynamics
The third law of thermodynamics states that the entropy of a perfect crystal of any pure substance approaches zero at absolute zero temperature. Entropy is sometimes called waste energy. For this reason, there can be no physical system with lower entropy, so entropy always has a positive value.
Occasionally, the second law of thermodynamics is called a law of energy depletion.
Example: This is why we cost money to run an air conditioner.
The second law is applicable to a wide variety of processes such as reversible and irreversible.
- Third Law of Thermodynamics
The third law of thermodynamics states that the entropy of a perfect crystal of any pure substance approaches zero at absolute zero temperature. Entropy is sometimes called waste energy. For this reason, there can be no physical system with lower entropy, so entropy always has a positive value.
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