The discussion revolves around the work done in an adiabatic process, specifically focusing on the formula W=(C/1-y)(Vf^(1-y)-Vi^(1-y)), where y is the ratio of specific heats Cp/Cv. Participants express confusion regarding the variable C and its relation to other constants in thermodynamics.
The discussion is active, with participants exploring different interpretations of the formula and the conditions of adiabatic processes. Some guidance has been provided regarding the use of constants and the relationships between pressure, volume, and temperature in adiabatic conditions.
Participants note that the typical ideal gas law may not apply in the same way during an adiabatic process, leading to further exploration of the implications of this distinction.
The C is usually expressed as K as in: [itex]PV^\gamma = K[/itex]. So it can be written:JustinLiang said:Homework Statement
On my formula sheet I have this:
W=(C/1-y)(Vf^(1-y)-Vi^(1-y))
y=Cp/Cv
Homework Equations
The Attempt at a Solution
I am confused about what the C in C/1-y stands for. My textbook does not even have this formula and I realized that C is not Cp or Cv...
Andrew Mason said:The C is usually expressed as K as in: [itex]PV^\gamma = K[/itex]. So it can be written:
[tex]W = \frac{P_iV_i^\gamma}{1-\gamma}(V_f^{1-\gamma} - V_i^{1-\gamma})[/tex]
AM
You can make it Vf and Pf or any V, P during the adiabatic process if you like:JustinLiang said:Ahh ok thanks! But why is it Vi and Pi, why not Vf and Pf? Is there a reason?
Andrew Mason said:You can make it Vf and Pf or any V, P during the adiabatic process if you like:
[tex]P_iV_i^\gamma = P_fV_f^\gamma = PV^\gamma = K = \text{ constant}[/tex]
AM
If PV=nRT and PV = constant then T would be constant (assuming n is constant). But in an adiabatic process that does work this cannot be the case: dQ = 0 -> dU = -dW where dW is the work done by the gas. So P1V1 ≠ P2V2.JustinLiang said:Okay, so for an adiabatic process, we cannot use the typical ideal gas law P1V1=P2V2 right?
What about PV/T=PV/T?