What Is the Heat Capacity in an Isothermal Process?

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SUMMARY

The heat capacity in an isothermal process is defined as C = ΔQ/ΔT. In this scenario, since the temperature change (ΔT) is zero, the expression leads to an undefined situation for heat capacity when ΔQ is greater than zero. The discussion emphasizes that while work is done in an isothermal process, there is no change in internal energy, which complicates the calculation of heat capacity. The key takeaway is that for isothermal processes, heat capacity cannot be expressed in traditional terms due to the constant temperature condition.

PREREQUISITES
  • Understanding of thermodynamic processes, specifically isothermal and constant volume processes.
  • Familiarity with the first law of thermodynamics and the relationship between heat, work, and internal energy.
  • Knowledge of the ideal gas law and its application in thermodynamic equations.
  • Basic calculus to comprehend the derivation of thermodynamic equations.
NEXT STEPS
  • Explore the implications of the first law of thermodynamics in isothermal processes.
  • Study the derivation and application of the ideal gas law in various thermodynamic scenarios.
  • Learn about the concept of heat capacity in different thermodynamic processes, including adiabatic and isochoric processes.
  • Investigate the relationship between work done and heat transfer in isothermal processes using graphical methods.
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Students studying thermodynamics, educators teaching heat transfer concepts, and professionals in engineering fields focusing on energy systems and thermodynamic cycles.

maurice2705
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Homework Statement


The question is presented as picture.


Homework Equations


What is the expression of this 'heat capacity C'?
The x-process is isothermal then C=nCΔT=0?
Please give me some ideas.

The Attempt at a Solution


set V1=V2, V3=V4, T1=T4, T2=T3, p1+p0=p2, p3-p0=p4
constant volume process:ΔU=n*Cv*(T2-T1)=Cv*V1*p0/R where p0=p2-p1
isothermal process:W=nRT1*ln(V3/V2)=nRT1*ln(p2/p3)
Then I can't go any further.
 

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maurice2705 said:

Homework Statement


The question is presented as picture.

Homework Equations


What is the expression of this 'heat capacity C'?
The x-process is isothermal then C=nCΔT=0?
Please give me some ideas.

The Attempt at a Solution


set V1=V2, V3=V4, T1=T4, T2=T3, p1+p0=p2, p3-p0=p4
constant volume process:ΔU=n*Cv*(T2-T1)=Cv*V1*p0/R where p0=p2-p1
isothermal process:W=nRT1*ln(V3/V2)=nRT1*ln(p2/p3)
Then I can't go any further.
Heat capacity is defined as: C = ΔQ/ΔT. Since work is being done but there is no change in internal energy, ΔQ > 0. However, since it is isothermal, ΔT = 0. So what is the heat capacity, ΔQ/ΔT at all pressures (points) on the isothermal curve?

AM
 

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