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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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52 views

Reversible and Irreversible Processes in a Cyclic Model with a Piston

I have a question that pertains to how we can recover the initial or previous state in a reversible process and how that becomes impossible with an irreversible process. In the quasit-static model ...
129 views

Released-absorbed heat relation in irreversible process

suppose we have an irreversible process, caused by a pressure difference $p_1 \neq p_2$ between two separated gases. The whole system is insulated. The two gases are separated during all the process, ...
59 views

Can you suggest a reversible process whereby heat can be added to a system? Would adding heat by means of a gas stove be a reversible process?

Can you suggest a reversible process whereby heat can be added to a system? Would adding heat by means of a gas stove be a reversible process? I am trying to understand thermodynamics and the whole ...
30 views

If a thermodynamic cycle on a Pressure-Volume diagram has internal irreversibilities, what does the area enclosed by the cycle represent?

When a cycle is internally reversible, the area enclosed by its P-v or T-s diagram is the net work, but what about when the cycle is internally irreversible? Is it net useful work on the surroundings ...
76 views

Free adiabatic expansion is REVERSIBLE. Spot the mistake in this argument

So I know for a fact that free adiabatic expansion is irreversible. I thought of the following argument which shows that free adiabatic expansion is reversible and I wanted to know where's the mistake ...
63 views

Can I tell whether a cycle is reversible or not by the $p$-$V$ diagram?

A thermodynamic process is reversible if the system remains in the equilibrium state throughout. That's what we are told in the book. My doubt is, though, can we judge whether a process is reversible ...
106 views

For irreversible processes , why is $\frac{Q_1}{T_1} < \frac{Q_2}{T_2}$?

In the book of Kondepudi & Prigogine, Modern Theormodynamics, at page 97, it is stated that All real heat engines that go through a cycle in finite time must involve irreversible processes ...
42 views

Comparison of work in reversible and irreversible processes

My teacher said that there is always wastage of work in irreversible process and that work in an irreversible process is always less than that in a reversible process even if one is adiabatic and the ...
60 views

Is Einstein's Photoelectric effect a reversible phenomenon?

If one emits a light beam in a given frequency (obviously there is a threshold frequency) over a metal plate, even on low energies, some electrons could be ejected and one could been measuring an ...
142 views

Why free expansion of a gas is irreversible?

A generic process is defined reversible if with its reverse is possible to come back to the orginal thermodynamic states both for the system and for its enviroment. You consider a room divided into ...
44 views

A query on the equation $TdS = dU + PdV$ (relating to phase changes)

$TdS=dU+PdV$ is one of my favourite equations in all of physics. I have used it many times, in particular to obtain the Helmholtz free energy; my favourite state function. One thing I am not 100% ...
22 views

Process both isothermal and adiabatic

Why a reversible process can't be both isothermal and adiabatic, while an irreversible one can be?
103 views

Thermodynamic definition of entropy describing reversible processes

I've recently started learning about entropy. One possible definition is that it is the logarithm of number of microstates of particles. Another possible definition is that for a reversible (...
123 views

What does the time reversibility of the laws of physics mean for causality?

Does the fact that the fundamental laws are symmetric with respect to direction of time show that causation does not exist? Since causality always requires the cause to precede the effect, but laws of ...
63 views

Are slow isobaric processes necessarily reversible?

All isothermal and adiabatic processes are reversible when carried out very slowly. Is it true for the isobaric process too? As isobaric process can also be carried out very slowly.
122 views

Entropy change in reversible and irreversible processes

$dS = dq/T$ for a reversible process and $dS \gt dq/T$ for an irreversible process, but why is the entropy change greater in an irreversible process? What difference between the two processes in ...
107 views

Increase in entropy and integer factorization (How much work does one have to do to revert “irreversible” processes?)

This is not necessarily a direct physics question, but I am hoping, that by posting it here, someone can give a hint from the physics perspective. It is known, albeit not proven, that integer ...
26 views

Do irreversible processes indicate that time reversible symmetry is a limited phenomenon instead of a universal law? [duplicate]

Physics and chemistry indicate various irreversible processes, while physics also proposes the theory of time reversible symmetry (T-symmetry). I suppose that evidence of irreversible processes ...
50 views

Work done by ideal gas under a reversible process which is not isobaric, isochoric, isothermal, adiabatic

First post, sorry for the poor formatting. Question Consider a non adiabatic system closed to mass exchange where an ideal gas traverses along a reversible path from state: to . What is the work ...
32 views

Absence of dissipative forces in a reversible process

I can't understand why dissipative forces must be absent during a reversible transformation. Aren't they a way of exchanging heat with ambient? Since the system is allowed to exchange heat with the ...
152 views

Work done by reversible and irreversible process

Reversible work is greater than irreversible work and the examples given in the book are isothermal reversible work and isochoric irreversible work. The explanation is as following. "More work is ...
70 views

In thermodynamics, how do you determine whether a process in reversible or not?

The question is simple: In thermodynamics, how do you determine whether a process in reversible or not ? For example, consider an a balloon containing some $He$, which is expanding in a constant ...
54 views

2nd law of thermodynamics for non-quasistatic processes

The 2n law of thermodynamics can be stated in terms of entropy as follows $dS \geq \frac{dQ}{T},$ which holds for all quasistatic processes (reversible and irreversible ones). Is there a ...
37 views

Question reg. reasoning of deterministic reversible cyclical laws - The Theoretical Minimum

I recently started reading "The Theoretical Minimum: What you need to know to start doing Physics". In the first chapter, the authors define the "Minus-First law", and state that reversible ".. laws ...
361 views

Heat transfer reservoir and system at same temperature

I just read that "a heat transfer between a reservoir and a system at same temperature is a reversible process". If there's no temperature difference, why would there be a heat flow?
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Proving that $dS$ is an exact differential mathematically

OK...so I hope this is not too dumb a question: We know that we can express $dS$ as $$dS=\frac{dQ}{T}=\frac{C_v}{T}dT+\frac{R}{V}dV,$$ where $C_v$ is the thermal capacity at constant volume and $R$ ...
72 views

Calculating final pressure in irreversible adiabatic compression

I am trying to solve the following question. A gas is enclosed in a cylindrical can fitted with a piston. The walls of the can and the piston are adiabatic. The initial pressure, volume and ...
71 views

Reversible reaction for Entropy Change of Surroundings

When learning about Entropy in my introductory lecture, I learnt that in basic terms, entropy can be spoken about as $$dS = \frac{dq_{rev}}{T}$$ and the lecturer mentioned that as Entropy $S$ and $T$...
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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 ...
265 views

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 ...
640 views

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 (...
267 views

Change of entropy in irreversible process

When calculating entropy change for a irreversible process,do I assume a reversible path and then integrated it?
125 views

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 ...
126 views

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 ...
40 views

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 ...
60 views

Doubt in thermodynamics pressure volume work done

Why work done in irreversible process is not calculated as -$\int p_{internal} dV$ ?
140 views

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?
40 views

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 ...
78 views

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 ...
2k views

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 ...
258 views

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 ...
79 views

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 ...
381 views

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, ...
138 views

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 ...
125 views

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 ...
265 views

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 ...