SECOND LAW OF THERMODYNAMICS PREPARED BY, JIGNESH VANPARIYA ( ) DARSHN INSTITUTE OF ENGG. & TECHNOLOGY

Content Limitations of first law of thermodynamics Kelvin Plank statement Clausius Statement Equivalence of the Clausius and the Kelvin statements PMM-2

Since we had a First and second law of Thermodynamics. Then what is necessity of Introduction of Second Law of Thermodynamics We can get it by studying Limitations of First Law of Thermodynamics.

Limitations of First Law of Thermodynamics 1.No restriction on the direction of the flow of heat: the first law establishes definite relationship between the heat absorbed and the work performed by a system. 2.Does not specify the feasibility of the reaction: first law does not specify that process is feasible or not. 3. Practically it is not possible to convert the heat energy into an equivalent amount of work.

PRACTICAL EXAMPLES We cannot extract heat from the ice by cooling it to a low temperature. Some external work has to be done. Fuel once burned cannot be restored back to original form. Persons always grew old

Second Law of Thermodynamics

Kelvin – Planck Statement It is impossible to construct an engine, which is operating in a cycle produces no other effect except to external heat from a single reservoir and do equivalent amount of work.

Clausius Statement It is impossible to construct an engine, which is operating in a cycle produces no other effect except to external heat from a single reservoir and do equivalent amount of work.

Applications Heat Engine Heat Pump Refrigerator

Equivalence of the Clausius and the Kelvin statements 1.Violation of Clausius statement leading to violation of Kelvin- Plank statement 2.Violation of Kelvin-Plank statement leading to violation of Clausius statement

Violation of Clausius statement leading to violation of Kelvin-Planck statement

Violation of Kelvin-Plank statement leading to violation of Clausius statement

PMM-2 A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However it does violate the more subtle second law of thermodynamics. The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.

PMM-2

REFERENCE Wikipedia Engineering Toolbox Books: Engg. Thermodynamics by P.K Nag Engg. Thermodynamics by D.S Kumar Physics gala