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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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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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120 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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403 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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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 ...
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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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Irreversible process involving temperature change

I do get a sense of how intermediate states cannot be defined if pressure and/or volume are changed suddenly, but what if it is the temperature that is being changed suddenly? For instance, what I if ...
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Maximum velocity of piston pushed by a gas on adiabatic irreversible expansion [closed]

I am currently studying for my country's IPhO selection process and thermodynamics has to be one of my favorites right now. However I came across a very odd problem that is making me revise a lot of ...
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Can the ideal gas expand adiabatically and irreversely?

Suppose that the ideal gas is expanding adiabatically from the state $(P_1, V_1, T_1)$ to the state $(P_2, V_2, T_2)$ I think this process can be allowed to happen reversibly or irreversibly, but ...
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279 views

Entropy change in a reversible adiabatic expansion of ideal gas

Below is P-V curves of 1 mole of ideal gase for temperature 700K, 500K and 300K each. Now I would like to calculate entropy change of the system along the path from (1) to (3), which is adiabatic ...
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379 views

Adiabatic reversible and irreversible process

If I have 2 gases $A$ and $B$ which are at an initial state ($P_1$,$V_1$,$T_1$) and one gas say $A$ is taken through a reversible adiabatic process and the other gas $B$ through an irreversible ...
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Reversibility of ideal gas processes (isobaric and adiabatic processes)

In an isobaric process, how is it possible to be reversible. In the case that volume is decreased, lets say $2m^3$ to $1m^3$ (at infinitesimally small increments) at a constant $1$ MPa of pressure. ...
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170 views

Reversible and irreversible cycles: Changes in entropy of the system and the surrounding

Entropy is a state function. Is it true that at the end of a cyclic process, the change in entropy of the of the system and that of its surrounding are both separately zero irrespective of whether ...
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Energy transfers and entropy

What I understand so far: in processes where the form of energy is replaced with another form and/or energy is transferred (and so work is done), there is always some degree of loss of energy as heat ...
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Entropy: subjective lack of knowledge that leads to objective conclusions

There is something I really don't get about entropy. Let's consider a classical system (not quantum mechanics here). We can compute the entropy of a system via the formula $$S=-\sum_l P_l Log(P_l)$$ ...
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Is there an implemented example of an almost reversible heat engine?

I'm reading Feynman's discussion of Reversible engines (Vol I 44.3) in The Feynman Lectures on Physics. His discussion is very abstract, and leaves a lot of practical questions unanswered. Rather ...
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Allowed 2-qubit gates [closed]

I was working on some Quantum Information problems regarding allowed 2-qubit gates and got stuck. These are the proposed transformations: $|A\rangle |B\rangle \rightarrow |B\rangle|\overline A\rangle ...