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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Efficiency of Stirling engine and Carnot's theorem
I want to calculate the efficiency of this Stirling cycle for an ideal gas $pV = nRT$
The mechanical work is
$$
\Delta W_{12} = - \int_{V_1}^{V_2} p(V) \mathrm{d}V = -nRT_2 \ln \frac{V_2}{V_1}\\
\...
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Is there a quasistatic process that is not reversible?
I have seen several questions and good answers on the link between reversible and quasistatic processes, such as here or here. However, these questions only adress one side of the problem : a ...
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Quantum and classical physics are reversible, yet quantum gates have to be reversible, whereas classical gates need not. Why?
I've read in many books and articles that because Schrödinger's equation is reversible, quantum gates have to be reversible. OK. But, classical physics is reversible, yet classical gates in classical ...
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How slow is a reversible adiabatic expansion of an ideal gas?
A truly reversible thermodynamic process needs to be infinitesimally displaced from equilibrium at all times and therefore takes infinite time to complete. However, if I execute the process slowly, I ...
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Hawking radiation and reversibility
It's often said that, as long as the information that fell into a black hole comes out eventually in the Hawking radiation (by whatever means), pure states remain pure rather than evolving into mixed ...
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If entropy is a state function, then why is all the talk about reversible vs. irreversible processes?
So I'm preparing for my Thermodynamics undergrad exam, and I just can't wrap my head around the significance of reversibility vs. irreversibility of a process in relation to entropy. I mean if entropy ...
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How is entropy a state function?
Is there only one reversible way to move from one state to another?
If we consider two states $A$ and $B$ on an isotherm and we move from $A$ to $B$ by first reversible isochoric process and then ...
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Again: why do quantum computations need to be reversible?
In quantum computing, there is famous "law" which is to say that all the computation must be reversible. I understand that, for simplicity, it may be easier to consider reversible operation, and that ...
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Principle of Caratheodory and The Second Law of Thermodynamics
Background
Constantin Carathéodory formulated thermodynamics on a purely mathematical axiomatic foundation. His statement of the second law is known as the Principle of Carathéodory, which may be ...
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Reversibility = non-causality. Can this be right?
I read yesterday the Norton Dome's paper, which shows that some Newtonian systems can be non-causal, based on specific solutions of Newton's laws. The author justifies the solutions in very nice, ...
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How is this process not quasi-static yet reversible?
Consider a (adiabatic) canister with a piston containing some gas kept in a vacuum. There are two weights on the canister which equalize the pressure of the gas on the piston. Assume the system is at ...
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Where does the irreversiblity came from if all the fundamental interaction are reversible?
There isn't too much to explain:
We know that all fundamental forces are reversible then where does the irreversibility come from?
Edit: The following is edit based on comments:
Consider a block of ...
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Why is heat transfer reversible when temperature difference is infinitesimal?
I don't understand why heat transfer from hot reservoir to the system is considered reversible in this case:
$T_{reservoir}$ = $T_{system}$ + dT
but it's considered irreversible in this case:
$T_{...
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Intuitively, why is a reversible process one in which the system is always at equilibrium?
A process is reversible if and only if it's always at equilibrium during the process. Why?
I have heard several specific example of this, such as adding weight gradually to a piston to compress the ...
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Hysteresis and dissipation
Hysteretic phenomena are often linked to dissipation. When there is a hysteresis loop, the dissipated energy can usually be computed as the area of the cycle.
For example, in ferromagnetic materials, ...
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If quantum computation is reversible, what is the point of Grover's search algorithm?
Wikipedia et al say the following about Grover's algorithm:
Although the purpose of Grover's algorithm is usually described as
“searching a database”, it may be more accurate to describe it as
“...
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Why do reversible processes not increase the entropy of the universe infinitesimally?
The book Commonly Asked Questions in Thermodynamics states:
When we refer to the passage of the system through a sequence of internal equilibrium states without the establishment of equilibrium with ...
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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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Difference between Reversible and Irreversible processes in Physics vs. Chemistry
In Physics a reversible process is defined as one in which the system can be returned to its initial conditions via the same path (along the PV Diagram), and every point along the path is an ...
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What are entropy and reversible processes really?
I'm confused about the concepts of entropy and reversible processes.
Before explaining the definition of entropy, they used the term "reversible process" without defining it formally. Then, when ...
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Why is the work done in reversible process greater than work done in irreversible process?
I have read in my textbook that maximum work is done by gas in a reversible expansion, but I do not know the reason behind it.
Also is work done by gas maximum in reversible compression also?
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Why are Reversible Processes quasi-static?
I have heard that all reversible processes are quasi-static but I have not yet found a strong reason for the fact that no non-quasistatic process is reversible.
I have seen on some other answers that ...
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Is thermodynamic reversibility a function of path?
Question: given a path taken by a system through state space, is it possible to make a statement such as 'that path corresponds to an irreversible process' or 'that path corresponds to a reversible ...
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Why is work done equal to $-pdV$ only applicable for a reversible process?
In thermodynamics, when we're interested at gases, I know that the work done can be written to be $-pdV$ for a reversible process ($p$ is the pressure of the system, and $V$ is the volume of the ...
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How heat flow through finite temperature drop is an irreversible process?
Is it necessary that the drop/rise in temperature by flow of heat is irreversible?
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What experiment supports the axiom that quantum operations are reversible?
Among the axioms of quantum mechanics there is one axiom that says transformations of a quantum state need to be continuous, linear, and reversible (and this together with the other axioms results in ...
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Does there always exist a reversible path between two states?
For a reversible process it holds that $dS=\delta Q/T$. We thus get the fundamental relation of thermodynamics: $dS=dU/T+P/T dV$. The reasoning goes that because entropy is a state function, this ...
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Why is adiabatic process isentropic?
I have read that adiabatic process is isentropic because there is no heat exchange in an adiabatic process and thus no change in entropy.
But my question is - Even in adiabatic process, work can be ...
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A thermodynamic transformation that can be represented by a continuous quasistatic path in its state space may still be irreversible. Why?
A thermodynamic transformation that has a path (in its state space) that lies on the surface of its equation of state (e.g., $PV=NkT$) is always reversible (right?). However, if the path is a ...
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Thermodynamically reversed black holes, firewalls, Casimir effect, null energy condition violations
Scott Aaronson asked a very deep question at Hawking radiation and reversibility about what happens if black hole evolution is reversed thermodynamically. Most of the commenters missed his point ...
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Are reversible adiabatic processes always isentropic?
If my understanding is correct, neither reversible nor adiabatic processes are necessarily isentropic.
But are reversible adiabatic processes always isentropic?
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Thermodynamic reversible process
My book says
A process is said to be reversible if it is carried out
infinitesimally slowly so that in each step thermodynamic equilibrium of the system remains unchanged & any infinitesimal
...
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Quasistatic vs Reversible processes
Would it be fair to state the difference between quasistatic and reversible processes as follows?:
A process is quasistatic if at every point in the process the system is in equilibrium with itself.
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Why is the maximum work achieved in reversible processes?
Let us consider an ideal gas. Let it be present initially in a state $(p_1,v_1,t_1)$. Now let it be driven to another state $(p_2,v_2,t_2)$. Why is it so that during this process the maximum work can ...
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Physics without time
The structure of physical law as we generally recognize it today is firmly held together by the existence of time. Although physical laws can both predict and retrodict (reversible time does not break ...
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Is heat death reversible by thermal or quantum fluctuations given an infinite time?
I'm new here, so apologies if the question doesn't sound meaningful considering what physics is supposed to answer. I don't have a physics or mathematics background, but I did learn a few things about ...
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How to conceptually identify reversible and irreversible processes?
When I studied thermodynamics for the first time I didn't really get much the conceptual understanding on reversibility, but nonetheless I've got a rough understanding and a mathematical criterion for ...
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Melting ice: reversible or irreversible?
I am looking into whether the melting of ice (or any substance for that matter) at constant pressure and temperature is reversible or irreversible. Different sources say different things, and it may ...
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How can dynamics be reversible if inflation-style baby universe spawning is allowed?
I just finished readying Sean Carroll's book, "From Eternity to Here", and have a question about reversibility and inflation:
Assume inflation allows random quantum fluctuations to produce high ...
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In the Langevin dynamics: neglecting inertia. A mathematician trying to understand physics terminology
If we write the Langevin equation: for a particle with mass $m$, position $x$ and velocity $v$, with some damping coefficient $\gamma$,
$$ m dV(t)=-\gamma V(t)dt+dW(t) ,~~~~~~~dX(t)=V(t)dt.$$
Then as $...
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Does bitcoin mining take work?
I'm neither a professional in cryptocurrency nor physics, but an interesting idea occurred to me. Bitcoin involves mining, which generates a lot of heat as waste.
Is the amount of heat produced by a ...
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Assumptions of thermodynamic & chemical equilibrium in fluid-dynamics
I am reading about the Euler equations of fluid dynamics from
Leveque's Numerical Methods for Conservation Laws. After introducing the mass, momentum and energy equations, some thermodynamic concepts ...
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Is $dS=\frac{\delta Q_{irev}}{T}$ true for non-reversible processes?
The German Wikipedia reads
Das Differential $\mathrm {d} S$ ist nach Clausius bei reversiblen Vorgängen zwischen Zuständen im Gleichgewicht das Verhältnis von übertragener Wärme $\delta Q_{\mathrm ...
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When doing entropy calculations, why do you use the reversible heat for the system but the actual heat for the surroundings?
Let there be a system and surroundings. Let the system undergo an irreversible process. I understand that to calculate the entropy change of the system, one can use a reversible path between the ...
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Why is quantum mechanics reversible?
"Quantum mechanics is reversible" this statement is everywhere, some even said it's just an observed fact about the universe. I can't find a layman explanation or example why is it reversible?
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Which temperature does $T$ in Clausius inequality ($\oint \frac{\delta Q}T\le 0$) refer to?
I got a little confused about the temperature in Clausius inequality. As you can see in this answer of Luboš Motl, it seems that temperature is the temperature of the system.
But in some answers of ...
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Why must allowable physical laws have reversibility?
I'm watching Susskind's video lectures and he says in the first lecture on classical mechanics that for a physical law to be allowable in classical mechanics it must be reversible, in the sense that ...
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Is an interaction-free measurement an irreversible process?
From what I've understood from reading different online sources including PSE*, measurements in quantum mechanics are generally argued to be irreversible (at least, when a macroscopic measuring device ...
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$dU=dQ$ and $dU=TdS$, but $dQ$ not always equal to $TdS$? Why?
$$ dU = dQ+dW $$ $$ dU=TdS-pdV $$ The equations above are always true for a thermodynamic state of a certain system. Now let's say that we have a situation where $dW=0$, this tells us that $$ dU=dQ $$ ...
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How should I interpret this thermodynamic inequality?
I'm a little bit confused over the following inequality:
$$ dS > \frac{\delta Q_{irrev}}{T} $$
An infinitesimal change in entropy is defined in this way: $$ dS = \frac{\delta Q_{rev}}{T} $$
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