How do I find the work done in an adiabatic process?

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Discussion Overview

The discussion revolves around finding the work done in an adiabatic process, exploring the relationship between internal energy, work, and temperature changes in the context of thermodynamics. The participants engage with theoretical aspects and mathematical formulations related to the second law of thermodynamics.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant states that adiabatic work can be expressed as ##C_v(T_2 - T_1)##.
  • Another participant explains that for an adiabatic transformation, ##\Delta U = -W## due to ##Q = 0##, leading to the equation ##W = -\Delta U = n \cdot C_{v}(T_{1} - T_{2})##, questioning the absence of ##n## in the initial formula.
  • A participant suggests that the initial formula might refer to work "per mole" or "per unit mass," emphasizing that ##Q## is zero in an adiabatic process.
  • One participant requests a step-by-step derivation of the equation ## - \Delta U = n C_v (T_2-T_1) ##.
  • Another participant questions the straightforwardness of the derivation and asks for clarification on the definition of ##C_v## and the term ##nC_v\Delta T##.
  • A participant expresses uncertainty about the derivation process.
  • Another participant reminds others to conduct their own research before seeking help, in accordance with forum rules.

Areas of Agreement / Disagreement

The discussion reflects a lack of consensus on the derivation of the work done in an adiabatic process, with multiple viewpoints on the formulation and the inclusion of variables. Participants express differing levels of understanding and clarity regarding the equations involved.

Contextual Notes

There are unresolved assumptions regarding the definitions of variables and the conditions under which the equations apply. The discussion does not provide a complete derivation of the equations mentioned.

Ruby_338
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How come ##adiabatic \,work = C_v(T_2 -T_1)##
 
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If the transformation is adiabatic you have that ##\Delta U=-W## for the second law of thermodynamics because ##Q=0##. So ##W=-\Delta U = n\cdot C_{v}(T_{1} -T_{2})## where ## C_{v}## is the specific heat for constant volume and ##n## represents the mole. It is strange that in your formula there isn't ##n##...

Ssnow
 
Ssnow said:
If the transformation is adiabatic you have that ##\Delta U=-W## for the second law of thermodynamics because ##Q=0##. So ##W=-\Delta U = n\cdot C_{v}(T_{1} -T_{2})## where ## C_{v}## is the specific heat for constant volume and ##n## represents the mole. It is strange that in your formula there isn't ##n##...

Ssnow
Maybe he means "per mole" or "per unit mass.". Also, irrespective of the 2nd law, Q is equal to zero for an adiabatic process.
 
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I forgot to add the n. How did we get ## - \Delta U = n C_v (T_2-T_1) ## ?

Can you show me step by step?
 
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Isn't it straightforward? How is [itex]C_v[/itex] defined? What is [itex]nC_v\Delta T[/itex]?
 
I don't know XD
 
Then start by checking. Per forum rules you should do your legwork, not ask others to do that for you.
 
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Okay. Ill remember that
 

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