# First law of thermodynamics

As we know thermodynamics is a branch of engineering which mainly deals with the flow and heat and the changes caused by the heat energy to the system and the surroundings.

There is three basic law of thermodynamics which deals the whole concept of heat.

Let us see those are the –

• Zeroth law of thermodynamics
• The first law of thermodynamics
• The second law of thermodynamics

Coming to the first law

This law states that the total energy of an isolated system is always constant.

That means suppose there is a system with an isothermal wall that is conducting wall.
Then the difference between the heat transferred and the work is done on the system is the internal energy of the system. Mathematically we can say that,

`                           ∆u =q-w`

Where u stands for the internal energy of the system and Q stands for the heat transferred to the system, and w is work done by the system.
This law can also be written as the perpetual motion machine of the first kind is not possible. This law applies to the cyclic process and the closed system,

A perpetual motion machine is a machine that does not obey the first law of thermodynamics which means it delivers continuous work without losing any heat or without the intake of the heat.

This law was first discovered by Rudolf Clausius.
Now anything worth concluding is this law measures only the increment or the decrease in the total internal energy of the system . Internal energy is the random chaotic motion of the molecules.

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