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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Prove the statement below [closed]

If there exists an irreversible adiabatic process between two end-states, then there exists no reversible adiabatic process between them.
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Why the reversibility requirement in Clausius equality doesn't prevent defining the entropy from it?

In his original work Clausius defines the entropy from his equality $\oint \frac{\delta Q}{T}=0$, which holds for a reversible cyclic process. As it means the integral $\int \frac{\delta Q}{T}$ over a ...
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Obtaining the direction of flow from principle of increase of entropy?

Can we mathematically show that water flows from high-pressure region to low-temperature region and why particles flow from a region of higher chemical potential to lower on the basis of the principle ...
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Isothermal Irreversible process

I'm in high school and wanted to get a few things cleared up. Isothermal process is defined as a thermodynamic process where temperature remains constant. Does this mean that temperature remains ...
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Does first law contradicts 2nd law of themodynamics?

We can write first law of thermodynamics in two forms. $$dU=TdS-pdV$$ and $$dU=dq+dw$$ It is also true that $dw=-pdV$ therefore $TdS=dq$ for every process irrespective of reversibility. What I am ...
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Kullback-Leibler divergence as a measure of irreversibilty?

I watched this recent KITP webinar on Nonequilibrium thermodynamics for active matter yesterday. I saw that KLD(Kullback-Leibler divergence) is used as a measure to quantify irreversibility in the ...
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Why is the speed of a process related to how irreversible it is?

Almost any physics major is taught that By an infinitely slow process, one can change the state of a system from A to B in an irreversible manner. Normally, the above explanation is accompanied by ...
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How to prove the existence of a certain thermodynamic path between two points?

Suppose I have two points on a PV graph labeled as A and B both having same pressures (that is the process is isobaric) and the volume of A is less than that at B. How can we rigorously prove that ...
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Difference between reversible and irreversible heat transfer

Reference books define reversible heat transfer as heat transfer occurs across a infinitesimal thermal gradient i.e. dT and irreversible heat transfer as heat transfer across finite thermal gradient i....
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Can you plot irreversible but quasi static processes on a $pV$ diagram?

I've often heard that you can't plot irreversible processes on a $pV$ diagram, but what about in the case where you have a quasi static process with friction? There still exists a curve of ...
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Irreversible isothermal compression of a gas increases internal energy? (Thermodynamics)

This is what I know: A reversible process is a process which occurs infinitesimally slowly. If you're isothermally compressing a gas infinitesimally slowly, the walls of the container decrease (...
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What is the physical interpretation of the Helmholtz free energy for an isothermic, irreversible process?

$$dF=-SdT-pdV$$ For an isotherm, $dF=-pdV$, so $\Delta F=-\int^{V_1}_{V_2}pdV$. Thus, a change in the free energy tells us how much work has been done by or on the system. However, at this point the ...
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Help with 2nd Law and irreversibilty [closed]

This question is about the seemingly idealized notion of isolated systems and truly irreversible processes in the context of the 2nd Law. Here are the definitions and citations I'll use then my ...
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Entropy as a state function for irreversible paths

Searching Physics Stackexchange for entropy I have found several posts regarding entropy, lately most of the questions why entropy is a state variable. This got me thinking. I have understood so far ...
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When differential of $p$-$V$ $dW$ work equals $-pdV$?

The differential form of the first law takes the form $$dU=\delta Q + \delta W$$ or $$dU=TdS-pdV.$$ First, we know that $TdS=\delta Q$ for reversible process. So we can't say that $dU=\delta Q -pdV$. ...
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Entropy generation at the molecular level in a irreversible process

When we expand an gas irreversibly in an adiabatic process then there is intermolecular friction, but what exactly gets transferred to heat. I have read that the directed motion gets randomized. But ...
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$\oint{A}=0\implies$ A is a State function?

If $A$ is a thermodynamic variable (ex:Pressure, volume, entropy). then If $\oint{A}=0$, then does it imply that $A$ has to be a state function? I'm trying to prove that Entropy is a state function. ...
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Proof for $\oint \frac{dQ}{T}=0 $ in a reversible process

I'm actually trying to prove that Entropy is a state function. I get struck at the point where I need to prove that $\oint \frac{dQ}{T}=0 $ for a reversible process. Clausius in his book The ...
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Entropy change in a reversible and Irreversible path

Let's consider 2 cases. First where a system is taken from state 1 to 2 in a reversible path. Second where the same system is taken from state 1 to 2 in an irreversible path. Can we say that Entropy ...
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How to formalize taking line integral by a reversible or irreversible path?

In thermodynamics work can be done by moving alone a reversible or irreversible path. Physical definitions of reversible and irreversible processes is uncommon in thermodynamics textbooks. The main ...
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Free expansion of interacting electron gas is an irreversible process

Consider a number of electron in vacuum, confined in a bounded region. These electrons have interaction described by QED. At $t=0$, we allowed the system to evolve. Without doing any measurement on ...
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How does the author identifies the irreversible process coming from the pressure difference?

In the book of Prigogine, Modern Thermodynamics, at page 113, it is given the example of an irreversible expansion of a gas. In a reversible expansion of a gas, the pressure of the gas and that ...
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Would entropy maximized at equilibrium if there were no irreversible processes? [closed]

I have read this question, but it does not answer my question: In a truly ideal isolated system (say an ideal gas), it is quite possible that there is no irreversible process such that the net ...
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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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What does Max Planck mean by this quote?

It is quoted in Prigogine Modern thermodynamics at the page 105 from Max Planck that Whether reversible processes exist in nature or not, is not a priori evident or demonstrable.’ However, ...
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Hysteresis of a ferromagnetic material and reversibility

Suppose a virgin unmagnetized ferromagnetic sample is magnetized to complete saturation. Usually, when we reverse the magnetic field, the system does not retrace its path in the M-H plane and there is ...
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Heating of Water, Reversible/irrevserible process

I'm hoping that someone can help me understand this problem. I am determining which of these processes are reversible and irreversible. If we had some beaker of water at room temperature which came in ...
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Is it possible to deduce the second law of thermodynamics from the first?

Considering the First law of thermodynamics as an axiom dU=dQ-pdV for any infinitesimal process, we should be able to prove that for any reversible(quasistatic) and cyclic transformation, there is at ...
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Reversibility of equation $F=mv$ [duplicate]

Please read the following text. This text is part of Leonardo Sauskind's book. It says that the relation F = m v is reversible. Why?
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Reversibility of the rules of classical mechanics [closed]

In the book of classical mechanics, Leonard Susskind says that Aristotle's equation of motion (F = mv) is reversible. But in the second lecture Theoretical Minimum 'videos say that F = mv is not ...
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Does entropy depend on reversibility?

When going through a cycle of a process $A \rightarrow B \rightarrow A$, is the change in the entropy of the system always equal to $0$? Does the reversibility of the process change anything (done ...
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Is it possible for matter to occupy a singularity, which is the point of rupture of space time caused by a black hole?

Also, are singularities caused by blackholes reversible? May one do work to reverse the singularity or black hole? Do blackholes create permanent holes in space time, thereby shrinking space time, or ...
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Contradiction in definition of entropy?

I'm studying for my thermodynamics exam and I came across something which really confuses me. An infinitesimal change in entropy $ dS_{sys}$ of a system at temperature $T_{sys}$ during a reversible ...
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For what type of process, we can use $dq=Tds$?

For what type of process, we can use $dq =Tds$? Reversible or irreversible? If only reversible, how do we replace $dq$ in $dq=dU+ PdV$ by $Tds$?
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Feynman's Reversible Machine Argument

In Feynman's Lectures on Physics, in the lecture on the conservation of energy, he makes the following argument: Consider weight-lifting machines—machines which have the property that they lift ...
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Ideal Reversible Heat Engine Entropy

For an ideal reversible heat engine, what is the entropy change of the system (heat engine) after 100 cycles? What contribution does the heat engine make to the entropy change of the universe?
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Work done by a gas in an isothermal process

So the equation for reversible work is $xRT \sim \ln\left(v_2/v_1\right)$ where $x = \textrm{no. of moles of gas}$. This is calculated on the basis of internal pressure. This equation is also given ...
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What are the conditions on irreversibility of thermodynamical processes?

I know that for processes to exist, in the following entropy equation $dS/dt = {\dot Q}/T + {\dot\sigma}$ ${\dot\sigma}$ has to be equal or bigger than zero. The thing is that I also saw a version ...
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Why does the reversible adiabatic expansion do more work on the surroundings compared to the irreversible adiabatic expansion?

I am wondering why a reversible adiabatic expansion results in a higher work output on the surroundings though the irreversible adiabatic expansion has to overcome the frictional force and therefore, ...
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Reversibility of Hamiltonian dynamics

I'm trying to understand a very basic property of Hamiltonian dynamics. I don't have a physics background but I do know some mathematics. I want to understand why negating the momentum is equivalent ...
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Irreversible, Compression and expansion work for a piston with ideal gas

How can we calculate the work done by the piston or on the piston by including the internal pressure of the piston and not the external one. Because if the external pressure is doing work, the ...
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The reversible Carnot cycle is the most efficient between $T_2$ and $T_1$. Is it a form the second law itself?

The second law of thermodynamics proposed by Clausius, Kelvin, Carnot ..etc in its original form as T dS> dQ for irreversible process and Tds =dQ only for reversible thermodynamics process. This ...
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Why must all natural processes be irreversible?

My thermodynamics lecturer was talking about reversibility and the idea of spontaneous change and he mentioned that all natural processes are irreversible. Can someone offer some sort of proof or ...
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On the way adiabatic processes were defined in Blundell's Concepts in Thermal Physics

In Blundell's Concepts in Thermal Physics, page $117$, the author defines an adiabatic expansion as follows, The word adiathermal means ‘without flow of heat’. A system bounded by adiathermal walls ...
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$PV$ work for irreversible expansion vs. irreversible compression?

Assuming we have an ideal gas expanding against a pistom in a cylinder isothermally, then the pressure drops due to viscous strain within the gas and we can extract less work than for an reversible ...
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Proof all reversible engines operating between 2 reservoirs have Carnot efficiency, applied to irreversible engines?

https://www.ques10.com/p/7650/show-that-the-efficiency-of-all-reversible-heat-en/ I was trying to find proof about how all reversible engines have the same efficiency as Carnot engines and found a ...
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Less loss of energy in reversible process

Why is there less loss of energy in reversible process? I found this: The reversible expansion does the maximum amount of work because the gas is pushing against the maximum possible external ...
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How can this heat engine be considered a reversible process?

A heat engine operates between a body with finite heat capacity 𝑐 at initial temperature $𝑇_1$ and a reservoir at fixed temperature $T_2$. Show that the maximum amount of work that can be done is ...
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In an irreversible or reversible isobaric process, is $Q$ equal to $dH$? is $dH$ equal to $W$?

First of all, Is an irreversible isobaric process even considered a truly isobaric process? Or can it be neglected when considering generalized rules for isobaric processes? Heat added or removed to ...
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Can anyone prove this overstated-but-almost-never-justified fact from thermodynamics?

Clausius inequality states that $\oint {\delta Q\over T}$ equals zero for a system undergoing a reversible cycle, whereas it can’t be greater than zero for an irreversible cycle. But everywhere, I ...

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