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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Is it possible to know/compute measurment impact to infer state before collapse? [duplicate]
Let say we have the state $ |\varphi⟩ = \alpha|0⟩ + \beta|1⟩ $
Measuring this state provoke a change, $\epsilon$ to the system, $S$, making the state of $|\varphi⟩$ collapse to either $|0⟩$ or $|1⟩$.
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Can reversible computers really perform truly reversible computations in practice? [closed]
Someone once told me that with reversible computers there is no energy cost for the computation itself, there is only a cost for running the hardware. But is this true in practice, or is it only an ...
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Free energy change in reversible/irreversible processes
Yet another follow up to this question,
I am struggling to understand the example provided in Chet Miller's answer:
An example of this is expansion of an ideal gas in contact with an ideal constant ...
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Difference between Reversible and Irreversible processes in Physics vs. Chemistry
In Physics a reversible process is defined as one in which the system can be returned to its initial conditions via the same path (along the PV Diagram), and every point along the path is an ...
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Can someone explain this to me? About reversible computing with finite energy and thermal equilibrium
In Life, The Universe, and Nothing: Life and Death in an Ever-Expanding Universe, they examine the implications of dark energy on the ultimate fate of life.
Then they say this,
It was long thought ...
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$dq_{rev}$ and $dq$, which one is larger? [closed]
Im learning about entropy and some concepts makes me confusing.
For a reversible and irreversible process with a same initial state and final state, it is said that entropy change of a system is ...
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Why the third law of thermodynamics requires reversibility?
A possible expression of the third law of thermodynamics is that, it is impossible to reach absolute zero in a finite number of reversible transformations.
I'don't understand why the transformations ...
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Reversible thermodynamics processes
A problem asks me to find the entropy increment in the machine operating some thermodynamic cycle. Can I assume that any closed cycle can (theoretically) be obtained by using two reservoirs at some ...
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Why fast gas compression produces less heat?
From Schroeder Thermal Physics pg. 113:
As an example, suppose you have gas in a cylinder with a piston, and you hit the piston very hard, so that it moves inward much faster than the gas molecules ...
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A reversible transformation, but there is finite temperature heat transfer?
Suppose to have 3 heat reservoirs, the first at temperature $T_1$, the second at temperature $T_1+dT$ and the third at temperature $T_2>T_1$
Then, consider a system, which volume is constant, in ...
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What are the properties of reversible and irreversible thermodynamic processes?
why do we say that reversible processes are slow whereas irreversible processes are fast?
Rusting is irreversible yet slow
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Why can't a heat engine have 100% efficiency?
Using the idea of isotherms and adiabats, I came up with the following argument to convince myself. First imagine the working gas within the system being heated along an isochore (hence all heat ...
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Equivalence of various definitions of reversibility in classical mechanics
I was reading Classical Mechanics: The Theoretical Minimum by Leonard Susskind, and the definition of reversibility in that was:
Given a state of a system, then we know exactly what state it came ...
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Work done in an isolated system
Question: An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If $T$ is the initial temperature and $T^\prime$ is the final temperature then compare the final ...
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How can the Entropy (change in entropy) of reversible and irreversible process be the same? If Entropy of reversible process is 0
E.g., the change in entropy of a reversible process 0, then irreversible process should have 0 change in entropy. This question arose because I couldn't understand why generally work done by ...
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Reversible/Irreversible Fundamental Equation [duplicate]
I do have some problems in understanding how the fundamental equation may be written correctly.
For a closed system without chemical reactions (and compression work being the only form of work done), ...
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What is Entropy Balance Relative to (un)Compensated Heat of Clausius?
Consider the ideal Carnot cycle consisting of two ideal reversible isothermal stages at $T_0$ and $T_1$ and two ideal adiabatic reversible (isentropic) stages connecting them; assume that $T_0 > ...
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Why is the final temperature of irreversible adiabatic processes higher than that of reversible adiabatic processes?
Suppose an irreversible adiabatic expansion process and a reversible adiabatic expansion process are starting from the same initial state, say, P1V1. Now, let both of these processes have equal ...
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Are there any time irreversible processes on earth which aren't due to the sun?
The sun is very hot. The earth is cold. Energy always flows from hot to cold systems. Due to the temperature difference, useful energy can be imparted onto earth (i.e., blackbody radiation from the ...
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How do I prove reversible transformations are necessarily quasistatic without using entropy?
I have the following definitions:
A transformation is said to be quasistatic if it passes only through equilibrium states (that is, the thermodynamical coordinates of the system are defined at every ...
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How can we say that work done by carnot engine in a cycle equals net heat released into it even when it is operated b/w 2 bodies and not 2 reservoir?
When a carnot engine is operated between 2 reservoir then after each cycle it return to its initial state so change in internal energy is zero and so work done by it equals net heat released into it. ...
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How does a reversible Carnot cycle transform heat to work?
To make clearer what I am asking let me introduce a new terminology to avoid any misunderstandings. Let the heat flow, which is rate, between a reservoir and an engine be denoted by $\mathfrak J$ and ...
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Is it possible for the universe to return to the exact current state if information cannot be lost?
My understanding is that, if information in the universe cannot be lost, it will always be possible (in principle) to tell which prior state of the universe has led to the current state. Is this true ...
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Is determinism broken in special relativity?
Under classical mechanics, in an isolated system everything is deterministic given some initial conditions. Otherwise, we would have to consider some probabilities of interactions with the outside on ...
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Understanding page 141 of Blundell’s Concepts in thermal physics
On this page (in the second edition), there is a figure containing two states A and B of a system:
There are two paths between A and B: one is an irreversible change, and the other is a reversible ...
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Why isn't the free expansion of a gas in an adiabatic container isentropic?
If you expand a gas adiabatically using a piston, the process is isentropic. However, if you simply remove the piston and let the gas expand freely, the process is now not isentropic. What makes these ...
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Proof of Caratheodory's theorem
Caratheodory's formulation of second law of thermodynamics, also referred to as Caratheodory's principle states
In any neighbourhood of any thermodynamic state $P$ there exist states which are ...
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Understanding the use of $d$ and $\partial$ in thermodynamics
It seems a hundred variations of this question have been asked, and it's difficult to find which of those questions relates to exactly what I'm asking. My apologies if exactly this question has ...
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Defining reversibility without resorting to entropy
Is it possible to define the concept of reversible process without using any mention to entropy?
The Wikipedia definition of reversible process seems to accomplish this by stating that:
In ...
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Fundaments of thermodynamics and separating entropy
I tried to write down my "own" fundamental rules of thermodynamics, which I can then use as solid ground to understand the rest of the topic. The main thing I thought of is separating ...
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Questions about Maxwell's demon
I've been reading about Maxwell's demon and the current accepted solution for it (deleting information results in an increase in entropy), but there are two things I don't understand about the ...
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What are the requirements to apply the Laplace Law in Thermodynamics ? Reversible and adiabatic, or just adiabatic?
The Laplace's Law in thermodynamics states that an adabatic reversible transformation of a perfect gas verifies the following identity :
$$
PV^{\gamma} = cte \qquad \left( \gamma = \frac{C_p}{C_v} \...
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Can heat(?) flow from a cold object to hot object?
When we dip a spoon (stainless steel) into ice cream, does it becomes cold or stay the same temperature? If it does, can we say that heat(?) can flow from cold to hot objects?
Is this the reason ...
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Do irreversible thermodynamic processes CONSTITUTE time or do they MOVE IN time? [closed]
Time can be associated with irreversibility. A broken egg can't reassemble. Most, if not all, processes are irreversible and this is associated with time going in one direction. Ŕemarkably, living ...
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Entropy of a deterministic reversible system
Suppose a deterministic reversible system evolving from state A of gas located in a small bottle in an otherwise empty room, to state B where the gas is dispersed throughout the room.
Why is the ...
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Why is rapid expansion/compression reversible?
I am looking over the Otto Cycle on this MIT website and it says at one point "the processes from 1 to 2 and from 3 to 4 are isentropic" in reference to the expansion and compression of the ...
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Why is rapid expansion/compression considered a reversible/isentropic process?
I am looking over the Otto Cycle on this MIT website and it says at one point "the processes from 1 to 2 and from 3 to 4 are isentropic" in reference to the expansion and compression of the ...
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Why must all reactions be reversible according to thermodynamics?
I am reading the book "Models of Calcium Signalling" by Dupont et al., and on pages 31-32 the statement is made with regard to some previously written chemical reaction equations
We have ...
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Comparing the final pressures/volumes/temperatures of a reversible and irreversible adiabatic process
Consider $2$ ideal and identical gases $A$ and $B$ which are at the same initial state of ($P_1$,$V_1$,$T_1$).
$A$ is taken through a reversible adiabatic process and $B$ through an irreversible ...
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Are Hamilton's equations reversible?
Say I define a time dependent vector field $\Psi(t):\mathbb{R}^d\to \mathbb{R}^d$ as reversible (also here) if, for $f(x,y)=(x,-y)$, we have:
$$ f\circ \Psi \circ f =\Psi(-t)=\Psi^{-1}(t).$$
Just to ...
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Doubt in entropy change of environment in an irreversible isochoric process
I have read the following:-
The entropy change of the environment is calculated by $\Delta S_{env}=-\int \frac{dq_{sys}}{T} $ for that process. Unlike for a system, we do not assume a reversible ...
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Does $PV=nRT$ hold for the endpoints of an irreversible process? [closed]
I have read the following:-
$PV=nRT$ holds throughout a reversible process
$PV=nRT$ does not hold throughout an irreversible process because the ideal gas law is only applicable for gases in ...
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How can the temperature of the surroundings be constant during a reversible thermodynamic process?
I am having trouble reconciling the following statements I have recently learned about thermodynamics:
The temperature of the surroundings is taken to be constant (with only infinitesimal changes)
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Why aren't all irreversible processes isobaric?
I am slightly confused about graphs of irreversible processes. Firstly, they are difficult to find and whenever I find them the form is something similar to:-
I have read about the explanation given ...
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Using quasistatic processes to calculate quantities
This question is inspired by Reif Problem 5.5. Note that it is not a homework problem and, even if it were, my question only loosely relates to it.
A vertical cylinder contains $N$ molecules of a ...
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Why does a null entropy variation along a closed timelike curve imply a reversible process?
Carlo Rovelli in one of his articles from 2019 (reference: https://arxiv.org/abs/1912.04702) argues that time travel into the past are thermodynamically impossible:
For instance, if we want to travel ...
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What is the type of system, if I have an opened container with hot water inside, but no heat input to the system?
I have a school project, where I am trying to generate electricity using TEG modules that are attached to an aluminium container that contains hot water. The container is opened and there is no heat ...
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How to find a complete understanding the 2nd law of Thermodynamics in terms of forms?
I have two straightforward question, and below I introduce more context to interpret them:
What is, or is there, an order relation for forms that one can use to make sense of the 2nd law of ...
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Confusion with Gibb's energy [duplicate]
For a reversible process , I can show that $$\mathrm dG=0$$
For the same reversible process I can also prove that $$\mathrm dG=\mathrm dW_{\text{max, non } P-V\text{ work}}$$
Does that imply maximum ...
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What's the variation of entropy of an irreversible process?
I'm studying entropy, in particular the increase of entropy principle, and I have a doubt about the entropy variation of an irreversible transformation.
If I have two thermodynamic states, A and B, ...
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