All Questions
21 questions
0
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2
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159
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How do I find the entropy change of the universe for a not-completely-irreversible isothermic expansion?
My chemistry professor recently showed this in a presentation explaining thermodynamics. In particular, he used it as a demonstration that global entropy rises when starting from the assumption that ...
- 3
0
votes
0
answers
49
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Can a fixed amount of ideal gas undergo a reversible process when 2 of either pressure, volume, or temperature are held constant?
I've seen some problems where this was the case: a fixed amount of ideal gas underwent a reversible process where temperature varied while pressure and volume were both held constant. How could that ...
- 39
-4
votes
4
answers
182
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Derive $ΔS = Nk\ln(V/V_0)$ using fundamental equations of thermodynamics [closed]
I am considering a system with an ideal gas undergoing an adiabatic expansion. The initial volume is $V_0$ and final is $V$.
From this, How do I derive $\Delta S = Nk\ln(V/V_0)$ using fundamental ...
- 33
0
votes
2
answers
96
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Is this set up a reversible process and is the adiabatic equation of state applicable here?
I had this question in a recent test:
My teacher while discussing this question used the adiabatic equation of state PV^gamma=constant to solve for length L (options C and D). And used work energy ...
- 115
0
votes
1
answer
227
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Why does the answer here use $ \Delta S=Q/T$ even though this isn’t reversible? [closed]
This question for my thermodynamics course ends up using $\Delta S = Q_{\text{waste}} / T,$ but I was taught that $ \Delta S=Q/T$ is only valid if the process is reversible. The question makes it ...
1
vote
2
answers
308
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Entropy and Heat Conduction
For an Intro. Thermal Physics course i am taking this year, I had a simple problem which threw me off-guard, I would appreciate some input to see where i am lacking. The problem is as follows:
Does ...
- 143
0
votes
3
answers
215
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Two Polytropic and Two Adiabtic processes in Thermodynamic cycle [closed]
$1$ mole of an Ideal gas performs a reversible cycle with 2 adiabatic and 2 polytropic processes.
$A(P_0,V_0,T_0)$ to $B$ with $V_B=V_A/\lambda$ with an adiabatic process.
$B$ to $C$ with a polytropic ...
0
votes
1
answer
43
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What is reversible heat?
If found the following question while studying thermodynamics.
What is meant by "reversible heat" and when would it be a thermodynamic property (and when it wouldn't). I am not asking for the ...
- 1,171
0
votes
1
answer
1k
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Calculating final pressure in irreversible adiabatic compression
I am trying to solve the following question.
A gas is enclosed in a cylindrical can fitted with a piston. The walls of the can and the piston are adiabatic. The initial pressure, volume and ...
- 3
0
votes
1
answer
332
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$\dot{W}_{lost}$ due to irreversible processes in the condenser of a refrigeration system
The condenser of a refrigeration system steadily admits $\dot{m} = 50 g/s$ of saturated R134a with a pressure $P_1 = 650kPa$ and a quality $x_1 = 0.9$. The condenser rejects $\dot{Q} = 7kW$ of heat to ...
- 1
-1
votes
1
answer
578
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Maximum velocity of piston pushed by a gas on adiabatic irreversible expansion [closed]
I am currently studying for my country's IPhO selection process and thermodynamics has to be one of my favorites right now. However I came across a very odd problem that is making me revise a lot of ...
- 1,263
2
votes
1
answer
5k
views
Derive the Carnot Efficiency without using the Carnot Cycle? [closed]
How can you derive the Carnot efficiency using only properties of reversible cycles?
- 659
0
votes
2
answers
115
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Is my understanding of reversible and irreversible processes correct?
My question arises from the following exercise:
To answer the first question, since $PV = K$ as the process is isothermal, I can deduce that $P_2 = 2P_1$.
However, the next question made me ...
- 3,240
2
votes
3
answers
2k
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Is isothermal expansion of a gas a reversible process?
I have a homework question that asks me to calculate the change in the entropy during the isothermal expansion using the Sackur-Tetrode. Then, show that it is a reversible process.
I have finished ...
- 435
3
votes
1
answer
2k
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Prove all reversible heat engines that work between just two temperatures have the same efficiency
Can someone explain this explanation to me:
A completely different argument focuses on the requirement that the
device only move heat at one or other of the two temperatures. Then,
provided we ...
- 273
6
votes
5
answers
19k
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Change in entropy when mixing water at different temperature
Suppose two amounts of water of the same mass, but with different temperature, are mixed. Then the entropy of the hot water decreases, but the entropy of the cold water increases due to heat transfer.
...
- 285
0
votes
2
answers
929
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How is a irreversible process (conventionally) represented on a $T-S$ plane and why cannot it be (really) represented?
A reversible process can be represented on a $T-S$ plane, and the area under the curve is the heat exchanged by the system.
On $P-V$ plane a irreversible process is conventionally represented with a ...
- 2,637
1
vote
2
answers
949
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Question about reversible heat engine efficiency
I have a question regarding heat engines that cropped up whilst I was doing a practice question. I will summarise the results I obtained for the previous parts of the question so as to save your time. ...
- 41
0
votes
1
answer
1k
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A question about thermodynamic reversible process [closed]
I am a new learner of thermodynamics, and I have a question in my assignment:
Show that $W$ and $Q$ for an arbitraty mechanically reversible nonflow process are given by:
$$W=\int VdP - \Delta(...
0
votes
1
answer
146
views
What are the state variables like temperature after the system has done an adiabatic irreversible process? [closed]
Consider a system containing ideal gas which is initially at a volume $V_{1}$ and then suddenly its volume is increased to a volume $V_{2}$. What is the final temperature of the system if the initial ...
2
votes
1
answer
279
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Irreversible work
I'm having some trouble trying to find the irreversible work done by a perfect gas when expanding. I know that the reversible work is greater than the irreversible one, but how can I find the ...
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