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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Clarification on 2nd law of thermodynamics

I was reading Feynman lectures on the 2nd law of thermodynamics Now, what about the second law of thermodynamics? We know that if we do work against friction, say, the work lost to us is equal to the ...
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Can two different points can be connected by multiple adiabatic curves?

I was watching this Thermodynamics lecture and I have a question on the 1st law. More exactly on how different adiabatic curves can connect the same initial and final states. See the diagram drawn at ...
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What is the difference between two methods of calculating irreversible work in finite-time thermodynamics?

In finite-time thermodynamics, there are two methods for calculating irreversible work, derived from two different papers: Method 1 (from doi: 10.1103/PhysRevE.104.034117): Excess work: Work under ...
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Confusion regarding the equation $dS=\frac{\delta Q_{rev}}{T}$

In Reif's Fundamentals of Statistical and Thermal Physics he outlines a "proof" (sections 3.8 and 3.9) of the equation $dS=\frac{\delta Q}{T}$ for any quasi-static, infinitesimal process (i....
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Can ideal gas equation $PV = nRT$ be used in the intermediate stages of a irreversible and reversible process?

Suppose we have two processes, one is reversible and the other is irreversible. The ideal gas undergoes from state A to state B in both processes. I want to know that can I apply the formula $PV = nRT$...
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Feasibility of entropy at zero temperature

I remember a college lecturer of mine once gave me this equation of entropy during one of his lectures on thermodynamics: \begin{align*} \Delta{S} = \frac{ d {Q} }{T} \\ \end{align*} I found out ...
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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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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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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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