Advanced General Physics 323/324

Thermal Physics Unit T2 The Second Law of Thermodynamics

Prerequisites: T1

Overview: This unit is devoted to the second law of thermodynamics and involves some quite sophisticated ideas and reasoning. The nature of reversible processes is introduced and applied to the Carnot cycle for heat engines and refrigerators. The quantity entropy is defined, and the principle of increase in entropy in irreversible processes is discussed.


F. W. Sears and G. L. Salinger, Thermodynamics, Kinetic Theory, and Statistical Thermodynamics (S&S) Chapt. 5 - Entropy and the Second Law of Thermodynamics; Chapt. 6 - Combined First and Second Laws, excluding Sections 6-9and 6-12.

Comment: This unit involves some rather subtle ideas with great practical application. Make sure to get the definition of entropy clear, especially the connection to reversible processes .

After completing this unit you should understand::

  1. The Second Law of Thermodynamics.
  2. The Carnot cycle (see also Chapt. 4) .
  3. The meaning of entropy.
  4. Reversible processes.
  5. The principle of the increase of entropy.
  6. Enthalpy (see also Section 3-12, page 83).
  7. The key equation dU = TdS-PdV .


Chapt. 4: Problem 37; Chapt. 5, Problems 3,8,12,21,27; Chapt. 6, Problem 2.

  1. Work out all the formulas in Sec. 6-6 for the properties of a pure substance.

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