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Ch 20 The Second Law of Thermodynamics © 2005 Pearson Education

20.1 Directions of Thermodynamic Processes © 2005 Pearson Education

20.2 Heat Engines Efficiency of an engine © 2005 Pearson Education

20.3 Internal-Combustion Engines Cycle of a four-stroke internal-combustion engine © 2005 Pearson Education

Thermal efficiency in Otto cycle Otto cycle © 2005 Pearson Education

Diesel Cycle © 2005 Pearson Education

20.4 Refrigerators Coefficient of performance of a refrigerator © 2005 Pearson Education

20.5 The Second Law of thermodynamics © 2005 Pearson Education It is impossible for any system to undergo a process in which it absorbs heat from a reservoir at a single temperature and converts that heat completely into mechanical work, with the system ending in the same state in which it begin

20.6 The Carnot Cycle © 2005 Pearson Education

Heat transfer in a Carnot engine or Efficiency of a Carnot engine © 2005 Pearson Education

coefficient of performance of a Carnot refrigerator definition of Kelvin temperature © 2005 Pearson Education No engine can be more efficient than a Carnot engine operating between the same two temperatures

20.7 Entropy Entropy change in a reversible process © 2005 Pearson Education Entropy is used to measured of disorder

Example 20.6 One kilogram of water at 0 ℃ is heated to 100 ℃. Compute its change in entropy. One kilogram of water at 0 ℃ is heated to 100 ℃. Compute its change in entropy. ANS: ANS: © 2005 Pearson Education

20.8 Microscopic Interpretation of Entropy © 2005 Pearson Education For any system, the most probable macroscopic state is the one with the greatest number of corresponding microscopic state, which is also the macroscopic state and the greatest entropy

Microscopic expression for entropy © 2005 Pearson Education

The Kelvin temperature scale is based on the efficiency of the Carnot cycle and is independent of the properties of any specific material. The zero point on the Kelvin scale is called absolute zero.

© 2005 Pearson Education

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