Solution: Kelvin-Planck Statement & Heat Engine Operation Explained

In summary, the operation of a heat engine involves a heat flow out of a reservoir and the performance of mechanical work. This process does not violate the Kelvin Planck statement of the 2nd law because the heat engine also releases heat into a second, colder reservoir during its cycle, fulfilling the requirement set by the statement.
  • #1
neelakash
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1

Homework Statement



In the operation of a heat engine there is a heat flow out of a reservoir and a mechanical work W is done.Explain why this process does not violate the Kelvin Planck statement of the 2nd law.

Homework Equations


The Attempt at a Solution



My attempts:Please check if I am correct

Because in addition to the hot reservoir from which heat flows into
the system, the heat engine also discards heat into a second colder
reservoir during its cycle. Thus, it uses the second reservoir required
by the Kelvin Planck statement.
 
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Yes.
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1. What is the Kelvin-Planck Statement?

The Kelvin-Planck statement is a principle in thermodynamics which states that it is impossible to create a cyclic process that will convert heat into work without any other effects. Essentially, it means that it is impossible to have a perfect heat engine that will convert all of the heat energy it receives into work.

2. What is a heat engine?

A heat engine is a device that converts heat energy into mechanical work. It operates through a cyclic process of taking in heat, converting it into work, and then expelling waste heat. Some common examples of heat engines include car engines and steam turbines.

3. How does a heat engine work?

A heat engine operates through a process called the Carnot cycle, which involves four stages: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression. During these stages, heat is transferred into and out of the engine, and work is done on the engine by expanding and compressing a gas.

4. What is the efficiency of a heat engine?

The efficiency of a heat engine is the ratio of the work output to the heat input. It is expressed as a percentage and is always less than 100% due to the limitations of the Kelvin-Planck statement. The Carnot cycle is the most efficient heat engine, with an efficiency of 100% in theory, but in reality, no heat engine can achieve this level of efficiency.

5. How is the Kelvin-Planck statement important in thermodynamics?

The Kelvin-Planck statement is an important principle in thermodynamics as it sets a limit for the efficiency of heat engines. It also helps in understanding the concept of entropy and the second law of thermodynamics, which states that the total entropy of a closed system will always increase over time. The statement also plays a crucial role in the design and development of more efficient heat engines.

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