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Questions tagged [reversibility]

The potential for a thermodynamic process to be reversed in time. Alternatively, a quantification of how far an irreversible process is from being reversible, which relies on a comparison to a corresponding theoretical reversible process.

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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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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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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 ...
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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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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 ...
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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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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, ...
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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 ...
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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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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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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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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 ...
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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 $b$, $$\...
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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 ...
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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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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 ...
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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 ...
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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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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 ...
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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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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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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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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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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 ...
Gopal Kaushik's user avatar
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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 ...
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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 ...
More Anonymous's user avatar
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Why don't the first two laws of thermodynamics contradict each other?

The second law of thermodynamics states that the entropy of the universe increases over time and this has lead to theories like the heat death of the universe and the big rip. What this means in ...
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Why are quasi-static processes reversible? [duplicate]

When a thermodynamic system, like an ideal gas within a piston immersed in a heat bath, is subject to changes, such as compression or extension of the piston, then the work that can be extracted from ...
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Heat being transferred from colder object to hotter object

My son was watching a YouTube video on entropy (The Most Misunderstood Concept in Physics). At about 11:30, it said that in theory it is possible to observe, say, "heat" moving from colder ...
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Why the insistence that the process be reversible for $dW_{RWS} = -dF$ to hold (Helmholtz free energy)?

In a discussion about the (change in the) Helmholtz potential being interpretable as the maximum available amount of work for a system in contact with a thermal reservoir (i.e. the free energy), ...
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Quasi-static processes that are not reversible

I have just begun reading Huang's Statistical Mechanics textbook and am confused by his definition of a quasi-static process. In his definition, he states that a quasi-static process is one in which &...
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How to know when a reversible process between end states exists?

I am continuing to try to understand maximum work reversible processes (and a subset thereof -- Carnot cycles) better. I am here curious about the following system. (1) Consider one mole of a gas (...
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Callen's Maximum Work Theorem: why doesn't heat lost equal heat absorbed (and likewise for work)?

This question was, effectively, asked here (please refer to that question for additional context); however, I don't think the given answer is correct (or at least complete) despite my having added a ...
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Why is any real process which proceeds through non-equilibrium states necessarily irreversible?

As per the title, why is any real process which proceeds through nonequilibrium states necessarily irreversible? The question came up when reading Callen's definition of "reversible process" ...
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Reversibility and its surroundings

I was thinking about the definition of reversibility but there is something that I cannot understand. In real life the surrounding of a system (anything else in the universe) is always changing making ...
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Is there an equivalent of "adiabatic" for work (i.e. a workless transformation)?

In Fermi's Thermodynamics (1937), Chapter I, §1, he defines an isochore transformation as a transformation during which the system performs no external work He then discusses the case where the ...
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Question about "the nature of the gas" (TD transfomations)

$n = 1$ mol of a perfect gas pass from an initial state $A$ to a state $B$ though an isothermal transformation where $T_A = 300 $K and $V_B = 2V_A$. Then from $B$ to $C$ though an isochoric ...
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Can irreversibility arise from systems that are microscopically reversible? [duplicate]

I was reading about Feynman's sprinkler problem, and came across a paper that discussed irreversibility in ideal fluids. It quoted the fact that When a real fluid is expelled quickly from a tube, it ...
Jonathan Huang's user avatar
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2 answers
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When is a thermodynamic system isobaric?

I came across a problem where a piston and gas arrangement was present and it was heated, so if the piston is free to move we call it isobaric. But is it only true if it is quasi static (reversible ...
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Please explain why the Carnot cycle is reversible while the Otto cycle is irreversible using the kelvin or clausius statement of the second law [closed]

why is the Carnot cycle reversible while the Otto cycle irreversible according to Kelvin-planck statement
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Difference between spontaneous and irreversible process?

I am confused about the difference between a spontaneous process and an irreversible process. Based on what I read so far, both processes increase universe's entropy. I never heard of any reversible ...
John Davies's user avatar
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3 answers
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Are there known conditions that ensure infinite slowness is reversible?

A system has a Hamiltonian that depends on a few external parameters $V,X_1,X_2...$. $$H=H(V,X_1,X_2....).$$ We can assume the dependence is continuous enough. A process is in the limit of infinite ...
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What does $Q$ refer to in this inequality $\Delta S\ge\frac{Q}{T}$?

Entropy change of a system due to heat $Q$ can be expressed by the following inequality (assuming that temperature is constant): $$\Delta S_\mathrm{sys}\ge\frac{Q}{T} \tag{1}$$ It can be expressed ...
Jimmy Yang's user avatar
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How it is possible for entropy of universe to increase during reversible process?

To calculate the entropy change of the universe when a closed system undergoes an irreversible process, one must choose a reversible process and calculate the following integral $$\Delta S=\int \frac{\...
Jimmy Yang's user avatar

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