Thermal Physics: Energy change due to compression

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SUMMARY

The discussion centers on the concept of reversible processes in thermal physics, specifically regarding energy changes during compression in quantum systems. The textbook passage describes a system in a quantum state with energy dependent on volume, where mechanical work done during slow compression leads to energy change while maintaining the same quantum state. Participants clarify that pressure and temperature relate to macroscopic particle behavior, while quantum mechanics pertains to microscopic analysis, emphasizing the necessity of understanding both thermodynamics and statistical mechanics as foundational concepts.

PREREQUISITES
  • Quantum mechanics fundamentals
  • Thermodynamics principles
  • Statistical mechanics concepts
  • Understanding of reversible processes
NEXT STEPS
  • Study the principles of reversible processes in thermodynamics
  • Explore the relationship between quantum mechanics and thermodynamics
  • Learn about the implications of energy changes in quantum systems
  • Investigate statistical mechanics and its application to macroscopic systems
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Students and professionals in physics, particularly those studying thermal physics, quantum mechanics, and thermodynamics, will benefit from this discussion.

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This is not a homework problem but rather a passage from my textbook that I don't understand. I don't think I quite understand the concept of reversible processes. Here is the passage from my book:

"Consider a system in the quantum state s of energy Es. We assume Es to be a function of the volume of the system. The volume is decreased slowly by application of an external force. Let the volume change take place sufficiently slowly that the system remains in the same quantum state s throughout the compression...The mechanical work done on the system by the pressure in a contraction appears as the change of energy of the system."

My question is:
How is it possible that the system can remain in the same quantum state throughout the compression if the energy is changing? (I believe the system under consideration is in contact with a thermal reservoir). Is this a reversible process?

Thank you!
 
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What a strange book? What book is it?

Pressure and temperature are concepts that apply to the average behavior of large numbers of particles. Quantum mechanical analysis applies to only a few particles at a time.

I find it hard to imagine why it would be useful to try to blend quantum and thermodynamic views in the same description.
 
It's thermodynamics and statistical mechanics. Quantum is actually a pre-req.
 

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