Question about thermodynamics first law

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SUMMARY

The discussion clarifies that the equation dU = TdS - PdV is not limited to reversible processes but is a fundamental physical property relationship applicable to any material. This relationship describes the interdependence of changes in internal energy (U), entropy (S), and volume (V) between two neighboring thermodynamic equilibrium states. The equation is derived from the principles of thermodynamics, specifically the second law, and emphasizes that all variables involved are state functions, making them independent of the process type.

PREREQUISITES
  • Understanding of thermodynamic state functions
  • Familiarity with the first and second laws of thermodynamics
  • Knowledge of reversible and irreversible processes in thermodynamics
  • Basic grasp of differential calculus as applied to thermodynamic equations
NEXT STEPS
  • Study the implications of the second law of thermodynamics on state functions
  • Explore the derivation of thermodynamic equations from reversible processes
  • Investigate the role of entropy in irreversible processes
  • Learn about the applications of dU = TdS - PdV in real-world thermodynamic systems
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Students of thermodynamics, physicists, and engineers seeking a deeper understanding of energy relationships in thermodynamic systems.

Clara Chung
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I know that dS=dQ/T for reversible process,
is dU=TdS-PdV for reversible process only?
 
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Clara Chung said:
I know that dS=dQ/T for reversible process,
is dU=TdS-PdV for reversible process only?
This equation has nothing to do with any process. It is a physical property relationship that must be satisfied for any material, describing the relationship between the mutual changes in U, S, and V between and two closely neighboring thermodynamic equilibrium states of the material. This constraint is imposed as a consequence of the 2nd law of thermodynamics.
 
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Agree with Chestermiller, dU = TdS-pdV is nothing to do with the process, (reversible or irreversible), even though it is developed from the reversible process, since all of the qualities here are state functions. Therefore, they are just related to the state.
 

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