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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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How to perform an isothermal reversible expansion?

Take the case of an isothermal reversible expansion of a piston to lift a weight. As the piston expands, the temperature remains constant, but the volume increases. This volume increase implies a ...
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Reversible vs. Irreversible Expansion

Suppose I have a gas in a piston expanding adiabatically against atmospheric pressure. If I do this reversibly, the final state is uniquely specified by the final volume $V_F$ of the gas. What ...
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Why the entropy change is not zero in the irreversible adiabatic process?

Why the entropy change is not zero in the irreversible adiabatic process? while it is defined as the integral of the heat added to the system over its temperature
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Joule free expansion and differentials in irreversible processes

I am studying thermodynamics (undergraduate level) and I am not sure I understand what happens in irreversible processes. I thought I understood but then I got confused in the Joule free expansion (...
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Change of entropy in irreversible process

When calculating entropy change for a irreversible process,do I assume a reversible path and then integrated it?
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Better understanding the Clausius Inequality

My conceptually understanding draws on the section on the Clausius Inequality from Finn's Thermal Physics. Attached is the graphic used for the derivation in the textbook. If I'm to understand ...
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Why is bringing two object to their initial temperature an irreversible process?

In the lectures, given in here, it is stated that We can imagine thermodynamic processes which conserve energy but which never occur in nature. For example, if we bring a hot object into ...
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Is there experimental evidence for the irreversibility of the collapse of the state of a system due to a measurement?

It has been pointed out by one of my professors that, in quantum mechanics, the collapse of the state of the system by measurement is not time-reversible, i.e once the system collapses due to a ...
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Deriving the second law of thermodynamics from an irreversible carnot process

I have studied the ideal carnot cycle extensively where we assume that $$\Delta S_{\mathrm{total}}=\sum_i \frac{Q_i}{T_i} =0$$ Now I was wondering whether it is possible to derive basic properties ...
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Doubt in thermodynamics pressure volume work done

Why work done in irreversible process is not calculated as -$\int p_{internal} dV$ ?
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Why do energy transfers always result some heat loss?

explain that energy transfers and transformations in mechanical systems always result in some heat loss to the environment. Like why is it necessary for a heat loss?
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Relations derived from ist law of thermodynamics

In the 5th point given in the image, it is mentioned that this relation is applicable for both reversible and irreversible processes, since the parameters involved are state functions i.e independent ...
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Explanation of a spring using “Artistotle's law of motion”, $\vec{F}=m\vec{v}$

So I was watching Susskind's Classical Mechanics lectures and I didn't understand something in the second lecture. He was telling about Aristotle's Law of motion which is $$\vec F = m\vec v.$$ He ...
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What is quasi-static process?

What is the formal definition of quasi static process? I am accustomed with it a bit intuitively, i want to know the formal definition of this. At some source I found the definition of somewhat ...
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The maximum work theorem for different reversible processes

Citing the Callen thermodynamics book (page 105): "for all processes leading from the specified initial state to the specified final state of the primary system, the delivery of work is maximum for a ...
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Why quasistatic doesn't imply reversible process? [duplicate]

Quasistatic process are almost always in equilibrium. We know that equilibrium implies zero entropy change. And zero entropy change implies that the process is reversible. So why quasistatic doesn't ...
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Irreversible and reversible compression work

Why is work done on the gas when it is compressed from (p2,V2) (pressure,volume) to (p1,V1) against constant pressure external pressure p1 maximum when it is done irreversibly? In reversible process, ...
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If irreversible process is quasistatic then can we find it's work using $pdv$ formula?

Now it's given on Wikipedia that quasistatic process can be irreversible,so can I find the work done by the closed system undergoing a process using $pdv$ work?...Next, is that work less than the ...
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How to calculate work for irreversible adiabatic processes?

By the first law, we know $\text{d}U=\delta Q+\delta W$ and, on adiabats, we know $\text{d} U=\delta W$. But what is $\delta W$ for irreversible adiabatic processes? Take a thermally isolated ...
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Why work done in irreversible process is not a state function?

Work done in irreversible process can be written as =P (external)(V2-V1). Here P(external) is the final pressure attained by the gas and V2=Final Volume V1=Initial Volume. Then all it depends on is ...
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Reversibility of compressed air sinking in water

Consider an apparatus in which air is trapped in a small insulated container with an open bottom, and weighted with weights so that the air is slightly above neutral buoyancy. This apparatus is ...
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Entropy generation in an endoreversible engine

An endoreversible engine is one that is internally reversible (i.e., a perfect Carnot engine) but the heat transfers occur across imperfect conductors (resistances), thus rendering the engine ...
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Why is the total change of entropy of a reversible process equal to zero

Why is it that, in order to attain reversibility, the temperature difference between the system and the surroundings must be infinitesimally small, I understand that it has to be quasi-static, but why ...
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Entropy and reversibility

I'm very confused right now, I need to make sure of the following if they're correct or not: A reversible path is a path in which if if you return back to your initial state, there would be no change ...
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Are the thermoelectric effects reversible?

On the one hand, it is commonly said that thermoelectric effects are reversible. For Wikipedia they are thermodynamically reversible because as the factor of merit ZT approaches infinity, the ...
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Does Isobaric process imply quasi-static?

For a system that undergoes a process that takes place at atmospheric pressure, the work done by the gas can be expressed as $-P_{\rm atm}\mathrm{d}V$. Does this mean that the process is always ...
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Rigorous definition of Hysteresis

I have been studying thermodynamics and have come across this concept of hysteresis but am struggling to find a rigorous way to define it. Here are the types of definitions I have come across Say a ...
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Is information lost in the Heisenberg's uncertainty?

If I set a particle at a known momentum and a known position, then I would expect that I know the precise position and momentum upon measurement (assuming I can measure that well). The uncertainty ...
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Source and sink in an ideal reversible otto cyle?

what the temperature of source and sink is in an otto cycle? Since the temperature of the surroundings continuously change during the isochoric parts, we cannot have a single source and sink ...
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Efficiency of reversible carnot engine must be 0?

In order for heat to transfer in a reversible process, the temperature difference must be approximately zero. Therefore at the isotherms in a carnot engine, there is negligible temperature difference. ...
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Trying to get one step closer to the understanding of free energies $F$ and $G$

I find it quite hard to get a good grasp of the notions of Helmoltz and Gibbs free energy, because they can be introduced in so many different ways, and embody so many different ideas at once... Here,...
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Irreversibility and increase of number of microstates

We know,in an irreversible process,always entropy of an isolated system increases,from Clausius inequality.Again,entropy is the logarithm of the number of accessible microstates of a system.How can we ...
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How can a reversible path be substituted by a reversible zigzag path?

Say I have a thermodynamic process with parameters P,T,V [Pressure, temperature and volume], path starting from an initial state to a final state, to go back to the initial state we have to stay in ...
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$dQ=Tds$ and quasistatic process

See Ján Lalinský's commment on Entropy $dQ=TdS$ and Work $dW = -pdV$ conditions? My question are: Is there a way to prove that $dQ=Tds$ is a quasistatic process? What's the funcitonal description ...
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How is a superconductor maintaining a persistent current a reversible process?

Once an electric current is established, and then the external electric field/voltage is withdrawn, a superconductor maintains the current forever. Such a process neither violates the first law nor ...
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Reversible compression of a gas - faulty reasoning?

I am trying to figure out where my reasoning falls apart in this thought experiment: To determine if a process "A" is reversible (or at the very least internally reversible), I try to picture a ...
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Can I uncut a piece of paper?

I've inadvertently cut a piece of paper that I wasn't meant to. I've repaired it pretty well using single sided sticky tape and I think, so long as no-one looks at it too closely, I'll get away with ...
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What happens to the heat generated in an irreversible process?

I know that a reversible process does more work than an irreversible process and that extra work is turned into heat. But what does that heat do? Does it increase the temperature?
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Why can't we plot irreversible processes on a $T$-$S$ diagram?

In the book "Heat and Thermodynamics" by Zemanky, It is stated that "only reversible processes can be plotted on a $T$-$S$ diagram. Since the definition of entropy involves a reversible change in ...
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Confusion on work done in reversible and irreversible process and others

I am greatly confused with the following things Work done in reversible and irreversible process Here: Since first law is only the energy conservation, if you have a gas, closed with a movable ...
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Total Reversibility of Carnot Cycle

I was reading about Carnot cycle in "Thermodynamics by Cengel & Boles", now it is stated that Carnot cycle is a totally reversible cycle, i.e it is an internally as well as externally reversible ...
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Quasi Static Reversibility Theorem

As far as I know, the definition of a reversible process is simply "a process that can be reversed". Meaning, that for an isolated global system containing the subsystem in question, its thermodynamic ...
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Why is it necessary to irreversibly erase a memory?

I know that the most accepted resolution of the Maxwell's demon paradox was proposed by Landauer and revolves around the fact that the demon's memory is finite and will have to be erased at some point....
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Does Irreversibly/no detailed balance implies there is no thermal equilibrium?

Consider the following transition matrix $$ T= \left[ {\begin{array}{cccc} \frac{1}{3} & \frac{1}{4} & \frac{1}{5} & \frac{1}{6}\\ \frac{1}{3} & \frac{1}{4} & \frac{1}{...
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Could a Carnot engine linked to a Carnot “refrigerator” create a perpetual heat flow between two reservoirs?

Here is a diagram of the system in question (adapted from the diagram on this page): All of the work produced by the Carnot engine is used to drive the Carnot refrigerator, which is simply a Carnot ...
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Inferring past heat distributions from present heat distributions

Solving the sourceless heat equation with dimensionless variables $u_{xx} = u_t$ on a disk with $u(x,0)=f(x)$, one gets under suitable assumptions: $u(x,t) = \sum C_n e^{-n^2t}e^{inx}$, $C_n$ being ...
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129 views

Why acting on a closed system infinitely slowly does not increase its entropy?

I don't understand why a finite-time process necessarily increases entropy while an infinite-time process might not.
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678 views

Internal energy of a reversible adiabatic process

what happens to the heat transfer and the internal energy in a system that undergoes reversible adiabatic process back to its original state. Bearing in mind that heat $Q$ was transferred at the ...
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172 views

Can you plot an irreversible cycle on a PV diagram?

You can only plot reversible processes in PV diagrams. And I suppose a cycle made of reversible processes should be reversible (am I right?). So every cycle plotted in a PV diagram should be ...
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Are zero heat exchange and zero work done synonymous to reversibility?

Instead of using the definition involving entropy or quasi-static processes, if I am simply able to prove that both work done (on the gas or by the gas, doesn't really matter) and heat exchange ...