What Variables are Zero in Different Thermodynamic Conditions?

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SUMMARY

This discussion focuses on identifying which thermodynamic variables—specifically work (w), heat (q), change in internal energy (ΔU), and change in enthalpy (ΔH)—equal zero under various thermodynamic conditions such as isothermal, adiabatic, and isobaric processes. The user seeks a comprehensive list that clarifies these relationships, particularly in scenarios like expansion into a vacuum and heating at constant pressure. The conversation highlights the need for a clear understanding of how initial conditions affect these variables in thermodynamic equations.

PREREQUISITES
  • Understanding of basic thermodynamic concepts such as work, heat, and internal energy.
  • Familiarity with the laws of thermodynamics, particularly the first and second laws.
  • Knowledge of different thermodynamic processes: isothermal, adiabatic, isobaric, and isochoric.
  • Ability to interpret and manipulate thermodynamic equations and variables.
NEXT STEPS
  • Research the implications of isothermal expansion on thermodynamic variables.
  • Study the characteristics of adiabatic processes and their effects on internal energy and enthalpy.
  • Examine the concept of expansion into a vacuum and its impact on work done (w=0).
  • Explore the relationship between pressure, volume, and temperature in isobaric processes.
USEFUL FOR

Students and professionals in physics and engineering, particularly those specializing in thermodynamics, as well as anyone looking to deepen their understanding of how different thermodynamic conditions affect key variables.

tyrasia
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Hello Everyone,

Is there a list online somewhere of which variable values are 0 and why (conceptually), based on initial conditions? Like I know that for a system at constant volume, w=0. I am looking for a list for the other effects like isothermal, adiabatic, what does pressure= if there is expansion in a vacuum (0?), isobaric, and such things like that. Thanks in advance!

Tyrasia
 
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I don't understand the question, more detail is better. What are the initial conditions? Presumably you are trying to solve some differential equation?

The example doesn't help me understand because "w" could be anything.
 
I am trying to find a list of what happens to the equations under conditions like, constant volume means work, or technically dw is 0. I know the equations (sorta) but don't know which terms will go to 0 under conditions likeisothermal expansion, expansion into a vacume, heating at constant pressure, adiabatic compression etc. when trying to find the values of q(heat),w(work),deltaU and deltaH given Volume and Temperature expanding in a vacume, for example, I got all 0s which I know is wrong. So I am looking for a list that can show me how the equations are affected by these conditions, or processes. Then I can figure out those 4 variables for a process which involves severel different processes sequential to each other.

Tyr
 

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