How many laws of thermodynamics are there? (3 or 4?)

There are total four laws of thermodynamics.

They are;

  • Zeroth law of thermodynamics
  • First law of thermodynamics
  • Second law of thermodynamics and
  • Third law of thermodynamics

Zeroth law

The zeroth law gives us the concept of thermal equilibrium

Zeroth law states that if two bodies are in thermal equilibrium with the third body, then that two bodies are also in thermal equilibrium with each other.

For more information on zeroth law, check out the ultimate guide on zeroth law of thermodynamics.

(From here, you will get all the details about the zeroth law along with real life examples and lots more)

First law

First law of thermodynamics gives us the concept of energy conservation. 

First law states that energy can neither be created nor destroyed. But it can only be transformed from one form to another.

Also the mathematical form of first law of thermodynamics (∆E = Q – W) indicates that the body possess internal energy which is equal to the heat supplied to the system minus the work done by the system.

For more information on first law, check out the ultimate guide on first law of thermodynamics.

(From here, you will get all the details about the first law along with real life examples and lots more)

Second law

Second law is related to the increasing entropy of the universe.

According to the second law, the entropy of the universe always increases for all spontaneous processes.

Also it states that spontaneous heat flow always takes place from a higher temperature body to a lower temperature body.

And if we want the heat flow from a colder body to a hotter body, then we need to supply work to the system.

For more information on second law, check out the ultimate guide on second law of thermodynamics.

(From here, you will get all the details about the second law along with real life examples and lots more)

Third law

The third law is all about the perfectly crystalline substance.

According to the third law of thermodynamics, if the perfectly crystalline substance is cooled up to absolute zero temperature (0 K), then its entropy will become zero.

For detailed information of third law of thermodynamics, visit the ultimate guide on third law of thermodynamics.

I hope this article has helped you in solving your doubts. If you have any questions, leave a comment below in the comment box.

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