Evaluation of work in thermodynamics

In summary, the conversation discussed the evaluation of work in a transformation from state A to B, where VB = 4VA and PA and VA are known. The question was raised about which value of pressure to insert considering it is not constant during the transformation. It was determined that VP2 must remain constant and can be expressed as a function of PA and VA. The final equation to solve for P and integrate between VA and VB was also provided.
  • #1
DottZakapa
239
17
Inside a cylinder with a sliding piston, n mole of monoatomic ideal gas at temperature TA occupy a volume VA at pressure PA, in equilibrium. The piston is expanded very slowly, turning the pressure in such a way that the product V⋅P2 remains constant till the volume VB .

I have to evaluate the work in the transformation from A to B:
VB = 4 VA
PA and VA are known

wAB = ∫ P⋅dV =

My question is:
- Which value of Pressure shall I insert instead of P considering the fact that it isn't constant during the transformation?
 
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  • #2
If VP2 remains constant, it must be equal to VP2 in state A. Can you write an equation to express this in terms of PA and VA?

Chet
 
  • #3
DottZakapa said:
My question is:
- Which value of Pressure shall I insert instead of P considering the fact that it isn't constant during the transformation?
Express P as a function of V.
 
  • #4
VA⋅PA2=VB⋅PB2
Then
PA=(VB½⋅PB)/VA½
and then I substitute in the integral:
∫ (VB½⋅PB)/VA½ dV

is it ?
 
  • #5
DottZakapa said:
VA⋅PA2=VB⋅PB2
Then
PA=(VB½⋅PB)/VA½
and then I substitute in the integral:
∫ (VB½⋅PB)/VA½ dV

is it ?
Not exactly. VP2=VAPA2

Solve for P and then integrate PdV between VA and VB.
 
  • #6
Aw ok! now i get it.
Thank you very much for your time. Very helpful.
Have a nice day : )
 

What is thermodynamics?

Thermodynamics is the branch of physics that deals with the relationships between heat, work, temperature, and energy.

Why is it important to evaluate work in thermodynamics?

Evaluating work in thermodynamics allows us to understand and predict how energy is converted and transferred in various systems and processes. This is crucial in many industries, including engineering, environmental science, and chemistry.

What are some common methods for evaluating work in thermodynamics?

The most common methods for evaluating work in thermodynamics include using mathematical equations, performing experiments, and using computer simulations.

What are the main factors that affect work in thermodynamics?

The main factors that affect work in thermodynamics are temperature, pressure, volume, and the type of thermodynamic process being studied.

How is work related to other thermodynamic properties?

Work is closely related to other thermodynamic properties, such as heat, entropy, and internal energy. These properties are interconnected and affect each other in various thermodynamic processes.

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