Why Is Entropy Considered a State Variable?

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SUMMARY

Entropy is classified as a state variable in thermodynamics, allowing calculations of entropy changes through reversible processes, as outlined in "Physics for Scientists and Engineers with Modern Physics" by Serway and Jewett, 7th edition. The discussion clarifies that while the entropy of a specific system can be reversible, the total entropy of the universe is not, emphasizing the distinction between local and universal entropy changes. This understanding is crucial for grasping the implications of entropy in both theoretical and practical contexts.

PREREQUISITES
  • Understanding of thermodynamics principles
  • Familiarity with state variables in physics
  • Knowledge of reversible and irreversible processes
  • Basic concepts of entropy and its implications
NEXT STEPS
  • Study the laws of thermodynamics in detail
  • Explore the concept of reversible processes in thermodynamics
  • Research the implications of entropy in real-world systems
  • Examine case studies on entropy changes in isolated systems
USEFUL FOR

This discussion is beneficial for graduate students in physics or engineering, educators teaching thermodynamics, and anyone interested in deepening their understanding of entropy and its role as a state variable in thermodynamic processes.

bradcliu
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Hi,

My name is Brad and I am a graduate electrical engineering student. Recently I wanted to go back and review and patch some holes in my head about fundamentals of physics. Therefore, I went back to my textbook Physics for Scientists and Engineers with Modern Physics by Serwey and Jewett, 7th ed. I wanted to understand a few questions I had about thermodynamics from years ago, and more specifically, about entropy.

In the text, it states that entropy is a state variable; therefore, we can find some path of reversible process that leads from one state to the next to calculate it. It never stated why it is a state variable or why the reversible path will work for irreversible or real processes. I can certainly calculate it. However, my understanding about this particular section is frustratingly vague. Please enlighten me Q_Q... Thank you.

Brad
 
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i guess entropy of the total universe if not reversible, but entropy of a particular system is reversible.

so if you made your desk messy, you can make it tidy again in a completely reversible fashion, but in the process introducing more entropy into the universe.
 

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