Why define entropy with heat instead of work?

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SUMMARY

The discussion centers on the definition of entropy in thermodynamics, specifically questioning why entropy is defined using heat (qrev/T) rather than work (wrev/T). Participants clarify that in the Carnot cycle, the sum of heat transfers divided by temperature results in zero, establishing entropy as a state function. The conversation highlights that while work can be associated with energy changes, it does not directly contribute to the entropy change when heat is added without performing work. Thus, entropy is fundamentally linked to heat transfer.

PREREQUISITES
  • Understanding of the Carnot cycle in thermodynamics
  • Familiarity with the first and second laws of thermodynamics
  • Knowledge of state functions and their significance in thermodynamic processes
  • Basic concepts of heat transfer and work in physical systems
NEXT STEPS
  • Explore the implications of the second law of thermodynamics on entropy
  • Study the mathematical derivation of entropy in the context of the Carnot cycle
  • Investigate the relationship between heat transfer and entropy changes in various thermodynamic processes
  • Learn about the concept of reversible and irreversible processes in thermodynamics
USEFUL FOR

This discussion is beneficial for students and professionals in physics, particularly those studying thermodynamics, as well as engineers and researchers involved in energy systems and heat transfer analysis.

Andrew U
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From what I understand, in the Carnot cycle summing qi/Ti for each step results in zero, thus indicating a new state function, entropy = qrev/T. But since dE = 0 = q+w, then q = -w, and looking at the equations derived from the cycle summing wi/Ti for each step should also result in zero. So why can't one also define entropy as wrev/T?
 
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Suppose you heat a body without doing any work. Does its entropy change?
 

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