JEE Main 2023 Thermodynamics Revision Notes

What is Thermodynamics?

Thermodynamics is a branch of Physics, which deals with the processes that involve heat transfer, work, and internal energy. Thermodynamics deals with the macroscopic states of matter.

• Joule studied the relationship of heat and its nature, and association to mechanical work.

• Thermal Equilibrium states that there are the same temperatures for systems.

• Internal Energy = Kinetic energy + potential energy of the constituents. 

• The thermodynamic system has equilibrium states shown by state variables.

• The particular state determines the state variable’s value, and not the path. Its examples include Temperature and pressure. 

• Zeroth law of thermodynamics: When two systems are in equilibrium with a given third system, it is necessary that they must be in  thermal equilibrium with each other.

• The thermodynamics first law is based on conservation of energy. 

• Efficiency of heat engine= Ratio of work done by engine to input. 

• The system as well as the environment comes back to the initial phase in a reversible process.

• The processes of nature cannot be reversed. The reversible process is a quasi static process that has no factors. This is a very slow process where the system is in equilibrium both thermal and mechanical with its environment. 

• The device that does a cyclic process that converts heat to work is known as heat engine.

• A reversible engine operates between two temperatures called Carnot engine, consisting of two processes connected by two adiabatic processes.

• Working substance of an engine does not determine the carnot engine’s efficiency, temperatures do.

• The efficiency of the Carnot engine is 𝜂 = 1 − TC/TH = 1 − (Temperature of cold reservoir/Temperature of the hot reservoir).

• The efficiency of a Carnot engine is more than that of an engine.

• When one cold body gains heat, another loses it.

• The flow of heat from cooler surroundings can result in hotter bodies.

• Kelvin's statement of second law states that there is no heat engine that converts with 100% efficiency. 

• Clausius' statement states that no process can be done when the only result is conversion of heat to work.

Thermodynamics is a crucial chapter because 3-4 questions with a weightage of 12-16% are expected to come from it in the JEE Main 2023. Keep reading to get a brief of the important topics covered in Thermodynamics. 

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