Pressure, volume and temperature in thermodynamics

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SUMMARY

The discussion focuses on the critical relationship between pressure, volume, and temperature in thermodynamics, emphasizing their role as state variables. It confirms that any two of these three variables can be selected for partial differentiation to derive quantities such as heat capacity. The specific heat capacities, Cp (at constant pressure) and Cv (at constant volume), are highlighted as essential concepts, with a clear connection established between them through the equations of state. The preference for using Cp in constant pressure scenarios is noted for its simplicity in equation formulation.

PREREQUISITES
  • Understanding of thermodynamic state functions
  • Familiarity with heat capacity concepts (Cp and Cv)
  • Knowledge of equations of state in thermodynamics
  • Basic principles of partial differentiation
NEXT STEPS
  • Study the derivation and applications of the first law of thermodynamics
  • Explore the relationship between Cp and Cv in various materials
  • Learn about the implications of constant pressure and constant volume processes
  • Investigate the role of state variables in thermodynamic cycles
USEFUL FOR

Students and professionals in physics and engineering, particularly those specializing in thermodynamics, heat transfer, and energy systems.

pivoxa15
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It seems there are 3 variables that are important for a particular state in thermodynamics, pressure, volume and temperture. For a state function like energy U, I can choose any two variables of the three above and do partial differentiations with it? So the two I choose is arbitary in order to work out quantities like heat capcity and the like.
 
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Yes - that's why two different specific heats (Cp and Cv) are defined and used. Of course Cp and Cv are related to each other, because, as you said, they are both consistent with the same equations of state of the material.

For example in a situation where the pressure is constant, it is obviously easier to write equations use Cp, rather than to use Cv and have extra terms in the equations because the volume is not constant.
 

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