All Questions
Tagged with irreversible or reversibility
646 questions
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Irreversible Processes in Thermodynamics
Here’s the updated text using dollar signs for MathJax formatting instead of parentheses:
Question: Understanding Work in Irreversible Processes in Thermodynamics
I am currently studying irreversible ...
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Whats the lowest energy substance reaches during adiabatic expansion of carnot engine? [closed]
In carnot engine we know the steps like first isothermal, than adiabatic, then reverse isothermal and adiabatic.
And we know that efficiency increase if the temperature of hot box(heat supllier) is ...
4
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2
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827
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Confusion about reversibility of a carnot engine
I recently posted a question about entropy and the conversation changed topic to bring up an interesting question. @Chemomechanics explained that for a transformation to be reversible it is needed ...
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71
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Entropy in a thermally isolated system
In page 141 of the book "Concepts in thermal physics" it is said that for a thermally isolated, the change in entropy is bigger or equal to 0 since $dQ=0$.
But since the system is thermally ...
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81
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Equilibrium in a reversible process
My lecture notes state the following (albeit in a very hand-wavy way):
If we
are gentle and careful however, we can change the state of the system slowly, making sure that while
the state is changing ...
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Generalization of Heat input in a $pV$ curve for a reversible process
I was wondering, is there a way to generalize by just looking at a PV curve for a certain process that heat flows into it or out of?
For example, for a cyclic process if the process is "clockwise&...
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Is interpreting information conservation as time reversibility non-mainstream physics?
I understand the following as standard results in modern physics.
Black holes evaporate over time via Hawking radiation.
Small black holes evaporate over very short times.
There is an "...
- 931
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Quasistatic and Reversible thermodynamic processes
A quasistatic process is a process where all intermediate states are in equilibrium. A reversible process is a process where no entropy (of the universe) is generated (and thus can be reversed to its ...
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50
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When considering the air friction, does the missile trajectory reversable?
When seeing a video of a missile hitting a target, someone would argue that it is fake, since the video is played backwards. I know that Newtonian mechanics is time reversal if we do not considering ...
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Why thermodynamic equilibrium and pressure balance is considered for having a reversible process? [duplicate]
When we compare the rapid expansion of an ideal gas to a very slow expansion from an initial state to a final state, we categorize one as irreversible and the other as reversible. This distinction ...
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3
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The development of Clausius Inequality
The reversible cyclic device absorbs $\delta Q_R$ from the thermal reservoir at $T_R$ and rejects heat $\delta Q$ to the piston-cylinder device, whose temperature at that part of the boundary is $T$ (...
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Why is the entropy change for a system in irreversible transformations the same as in reversible transformations in some cases, not in other cases?
Generally, the entropy change for a closed system for an irreversible transformation is not the same in a closed system for a reversible transformation.
A clear counterexample is that of an adiabatic ...
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Clarification on 2nd law of thermodynamics
I was reading Feynman lectures on the 2nd law of thermodynamics
Now, what about the second law of thermodynamics? We know that if we do work against friction, say, the work lost to us is equal to the ...
2
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2
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416
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Can two different points can be connected by multiple adiabatic curves?
I was watching this Thermodynamics lecture and I have a question on the 1st law. More exactly on how different adiabatic curves can connect the same initial and final states. See the diagram drawn at ...
- 1,131
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What is the difference between two methods of calculating irreversible work in finite-time thermodynamics?
In finite-time thermodynamics, there are two methods for calculating irreversible work, derived from two different papers:
Method 1 (from doi: 10.1103/PhysRevE.104.034117):
Excess work: Work under ...
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62
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Confusion regarding the equation $dS=\frac{\delta Q_{rev}}{T}$
In Reif's Fundamentals of Statistical and Thermal Physics he outlines a "proof" (sections 3.8 and 3.9) of the equation $dS=\frac{\delta Q}{T}$ for any quasi-static, infinitesimal process (i....
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Can ideal gas equation $PV = nRT$ be used in the intermediate stages of a irreversible and reversible process?
Suppose we have two processes, one is reversible and the other is irreversible. The ideal gas undergoes from state A to state B in both processes.
I want to know that can I apply the formula $PV = nRT$...
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49
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Feasibility of entropy at zero temperature
I remember a college lecturer of mine once gave me this equation of entropy during one of his lectures on thermodynamics:
$$
\begin{align*}
\Delta{S} = \frac{ d {Q} }{T} \\
\end{align*}
$$
I found out ...
- 41
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81
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Is the 2nd law a reason for the irreversibility of natural processes or a consequence of it?
I have been introduced to chemical engineering thermodynamics due to my academic background. I had learnt about internal energy, entropy etc and applied the equations to various scenarios of practical ...
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Entropy in irreversible adiabtic process
We know that,
$$dS=\dfrac{\delta Q_{rev}}{T}$$
If you have an irreversible adiabatic process between two thermodynamic equilibrium end states of a system, there exists no possible reversible adiabatic ...
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5
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674
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Use of Clausius theorem to prove entropy inequality in Fermi's Thermodynamics
At the beginning of Section 13 (at the bottom half of page 54 through the top half of page 55) of Enrico Fermi's classic Thermodynamics, he sets out to prove the relation (using his notation)
$$S(B) - ...
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108
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What is the relationship between Clausius Inequality and 2nd Law?
I am confused about the application of the 2nd Law for reversible and irreversible processes and cycles.
I want to know how the Clausius principle, the Kelvin-Planck statement, and the Clausius ...
- 31
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106
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What is the difference between a reversible process and an equilibrium? [closed]
I am confused about the differences between a reversible process and an equilibrium when considering their energy aspect.
Here is what I know so far.
(1) Equilibrium and Reversibility
Equilibrium ...
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Given a viably physical (isolated), quantum many body Hamiltonian, does an initial state of a superposition of energy eigenstates ever thermalize?
Given a viably physical, quantum many body Hamiltonian of a isolated system, if initially a state is prepared which is a superposition of energy eigenstates in an interval centered at E and E', not at ...
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71
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Can equilibrium thermodynamics be used to analyze irreversible processes?
As usually taught in undergraduate courses, classical thermodynamics is actually thermo-statics, the thermal physics of equilibrium states. Even in this very restricted form it can and does make ...
- 113
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41
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Is this a counterexample for the idea that reversible and quasi-static processes must infinitely slow?
Many people say that a reversible process must be quasi-static and infinitely slow. I (think I) understand the examples involving gases inside pistons to demonstrate the point, but I don't understand ...
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177
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Is stochasticity totally incompatible with current theories of conservation of information in quantum physics?
Most physicists accept the unitarity principle of the universe, according to which the state of a system at any given time must determine its state at any other time (information is never lost, ...
- 81
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27
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Distinguish a reversible process via measurements
Is it possible to distinguish between reversible and irreversible processes - say, the process of the working substance in a heat engine - via a measurement?
Its a bad question, in the sense that ...
- 273
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210
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Change in entropy in reversible and irreversible process
Let's take a process with constant pressure in ideal gas for example. in reversible process
$dS=\int_{1}^{2}\frac{\delta Q_{rev}}{T}=\int_{1}^{2}\frac{C_pdT}{T}$
Assuming constant specific heat ...
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113
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Clarification on the Use of $\frac{dS}{dE} = \frac{1}{T}$ vs. $\frac{dS}{dQ} = \frac{1}{T}$ in Thermodynamics
I'm currently studying thermodynamics and have encountered two expressions relating changes in entropy to temperature, but applied in seemingly different contexts:
$\frac{dS}{dE} = \frac{1}{T}$, ...
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48
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Why Onsager's formulation of thermoelectricity is better than Bridgman's?
General comment: despite the longish historical introduction this question is not about the history of physics but rather about a specific conceptual problem in physics.
Following Bridgman in the ...
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Why do we need an adiabatic expansion in the Carnot cycle? [duplicate]
As we know that 1st process is an reversible isothermal expansion during this the system is in quasi static equilibrium which helps in increasing the volume of the system but why does the second step ...
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151
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Irreversibility and organisation of trajectories in the phase space
I am currently thinking about the irreversibility paradox. I am not working in this area and my question is certainly not original but I couldn't see it stated in that form yet.
I can't grasp how are ...
- 163
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227
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Change of entropy of irreversible and reversible processes and cycles
Clausius' theorem states that
$$\oint\dfrac{\delta Q}{T}\leq 0,$$
$=$ for reversible cycles and $<$ for irreversible ones.
For a cycle with two reversible paths connecting points $a$ and $b$,
$$\...
- 420
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35
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Reversible processes in thermodynamics [closed]
These are a few basic questions of mine in thermodynamics whose answer I can't find anywhere.
$1$. How does a quasi static process serve the purpose of thermodynamic equilibrium?A quasi static process ...
- 379
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30
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Asymmetry when $t\rightarrow -t$ [duplicate]
If we consider the equation of critical damping $$x=(a+bt)e^{-ct}$$
then the graph is
However, it is asymmetric for positive and negative time values. I have an intuition that this should be the case ...
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1
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62
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Container divided by adiabatic wall with mass and friction: why is it a quasi-static process?
Thanks to the help of @ChetMiller, the following fact is essentially concluded in this thread. Consider a rigid, thermally isolated container divided by a massless barrier parallel to its base into ...
- 1,723
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243
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Container divided by frictionless adiabatic wall: reversible or irreversible process?
I have encountered an issue in the following physical situation. Consider a rigid, thermally insulated container divided by a barrier parallel to its base into two parts, left and right, each ...
- 1,723
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213
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Validity of the equation $dQ=CdT$ in different cases
I know this question may be too simple so I apologise for that but nonetheless very necessary. In my class we have defined the heat as $$\delta Q=CdT$$ with $C$ the heat capacity, but I'm unsure if it ...
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57
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Reversibility of the ideal Carnot cycle
How do adiabatic processes in the reversible Carnot cycle take place? Is the gas adiabatically isolated? If so, how would that happen in real life? (I know that Carnot cycle is not practically ...
- 1,131
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133
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Can any irreversible work source be simulated by a reversible work source?
In a textbook for thermodynamics, it considers a situation where work is done to a system by an irreversible work source through a thermally insulating piston, and it states "any irreversible ...
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158
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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 ...
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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 ...
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Change in entropy for a reversible process
The infinitesimal change in entropy of a reversible process is given by $\text{d}S=\frac{\delta Q}{T}$. How is this proven?
For a measurable change, $\Delta S = \int_{1}^{2} \frac{\delta Q}{T}$.
I'...
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217
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Increase of entropy when two reservoirs are in thermal contact
While reading my textbook , I came across a proof which intended to verify that entropy always increases when a hot reservoir is kept in thermal contact with a colder reservoir.
The proof goes as ...
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442
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Intuitive explanation for reversible and irreversible process
I have read that a reversible process is one in which $\Delta S_{\text{universe}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}=0$ and an irreversible process being one in which $\Delta S_{\...
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28
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Energy spread and reversibility of a thermodynamic process
Recently, while studying thermodynamics I came across something called a reversible process, textbook stated that an infinitesimally slow process can be termed as a reversible process.
This doesn't ...
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41
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The work and reversibility of an adiabadically stretched band
I currently working on this. More specifically I have a question about Problem 2.8 (solution on page 34 and exercise on page 25 of the pdf). I have 4 questions
1.
In the solution for b) the author ...
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Reversed time in Norton's dome
"Norton's Dome is a thought experiment that exhibits a non-deterministic system within the bounds of Newtonian mechanics. "
A ball rolled to the top can reach it in finite time with zero ...
- 3,001
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Gravitational waves from a time irreversible source? [duplicate]
So during the formation of a blackhole/particular phase transitions we have a time irreversible process occuring. How does one model the gravitational waves for such discontinuities in general ...
- 1,349