A important property of all systems in thermodynamics and statistical mechanics. Entropy characterizes the degree to which the energy of the system is *not* available to do useful work
1
vote
1answer
30 views
Volume quotient in Carnot-cycle
Problem:
One kilomole of an ideal, monatomic gas undergoes a reversible Carnot-processes between temperatures 300 °C and 20 °C. The work done during one cycle is 1500 kJ.
a) Find the ...
2
votes
0answers
54 views
Has Quantum Mechanics found violations of the 2nd Law of Thermodynamics? [on hold]
Has Quantum Mechanics found violations of the 2nd Law of Thermodynamics? Is there a quantum mechanical (QM) experiment that shows that entropy decreases for certain QM systems?
thanks
13
votes
2answers
201 views
Intuitive understanding of the entropy equation
In thermodynamics, entropy is defined as $ d S = \dfrac{\delta q_{\rm }}{T}$. This definition guarantees that heat will transfer from hot to cold, which is the second law of thermodynamics. But, why ...
5
votes
1answer
124 views
``What is life?'' by a physicist definition [on hold]
The question is about defining ``What is life?'' in the field of Physics.
Whether there is any (insightful) way of defining ``What is life?'' from physicists.
There are pioneer works, including ...
9
votes
3answers
219 views
Intuitive understanding of the definition of entropy
In Wikipedia, the definition of entropy goes like this: $ d S = \dfrac{\delta q_{\rm }}{T}$. The literal interpretation of this equation is that some amount of heat transferred into a system, if the ...
3
votes
2answers
63 views
Are reversible adiabatic processes always isentropic?
If my understanding is correct, neither reversible nor adiabatic processes are necessarily isentropic.
But are reversible adiabatic processes always isentropic?
15
votes
5answers
1k views
Why isn't absolute $0 K$ temperature possible?
So $T$ is defined as
$$T = \left(\frac{\partial E}{\partial S}\right)$$
and $S$ is defined as
$$S = k_B \ln \Omega$$
where $\Omega$ is the number of accessible states of the system for a given ...
6
votes
5answers
195 views
How do you prove the second law of thermodynamics from statistical mechanics?
How do you prove the second law of thermodynamics from statistical mechanics? To prove entropy will only increase with time? How to prove? Please guide.
4
votes
0answers
38 views
Victorian cosmology after the second law of thermodynamics but before relativity?
In the 19th century, most astronomers adopted an island universe model, in which our galaxy was the only object in an infinite space. They didn't know that the "spiral nebulae" were other galaxies. ...
2
votes
1answer
47 views
Equation of state of a rubber band
I have the following question that I attached in png format.
I have done part (a), but I am having difficulties in part (b) when I proceed according to the book. I have non zero tension at ...
3
votes
1answer
89 views
Second Law of Thermodynamics…confusion over an example
By the second law of thermodynamics, you shouldn't be able to use any amount of mirrors/lenses to focus sunlight onto an object and heat it past the surface temperature of the sun (approximately ...
3
votes
3answers
98 views
How does the entropy of an isolated system increase?
The change of entropy is defined $$\Delta S = \int \frac{dQ_\mathrm{rev}}{T}.$$ If a system is isolated the heat transfer between the system and the surroundings is zero ($dQ = 0$), thus $\Delta S = ...
0
votes
1answer
27 views
Entropy of mixing
Consider a binary alloy system of two distinct chemical components $A$ and $B$ whose atoms occupy distinctly numbered sites. The entropy associated with assembling such an alloy is known as the ...
0
votes
0answers
36 views
Is it correct to assume that a stretched rubber-band has negative entropy change?
If so, how could we express it in equations connecting S,T,Q? I was wondering if the net change is heat transfer was positive; Since we could feel the heat when it is stretched.
0
votes
0answers
39 views
Super cooled steam and entropy change
I was thinking about a situation where I have some super cooled steam which suddenly freezes to water.What are the entropy changes(positive or negative) for the system and the universe?
My ...
3
votes
2answers
121 views
Is it possible for the entropy in an isolated system to decrease?
As far as I can tell, the concept of entropy is a purely statistical one. In my engineering thermodynamics course we were told that the second law of Thermodynamics states that "the entropy of an ...
1
vote
1answer
60 views
Does a universe experiencing “heat death” have a temperature?
As defined by Wikipedia:
The heat death of the universe is a suggested ultimate fate of the
universe in which the universe has diminished to a state of no
thermodynamic free energy and ...
2
votes
0answers
64 views
The surface area to volume ratio of a sphere and the Bekenstein bound
I am trying to relate the surface-area-to-volume-ratio of a sphere to the Bekenstein bound. Since the surface-area-to-volume-ratio decreases with increasing volume, one would surmise that, per unit of ...
1
vote
0answers
15 views
Entropy used to calculate energy?
I'm currently reading an online article, and below is a quote from that article:
The thermodynamic entropy to change $n$ memory cells within $m$ states is $ΔS=k_B\ln(m^n)$, where $k_B$ is the ...
1
vote
1answer
37 views
What is the importance of state functions in physics?
I'm currently reading about the Carnot cycle and its significance on the formulation of entropy (because I want to try to understand the concept better), but I can't seem to answer the following ...
0
votes
2answers
35 views
Any closed system?
Is there any physical example of a real closed system?
I am aware that the whole universe can be considered as a closed system, but I am looking for a smaller example.
4
votes
4answers
266 views
Entropy as an arrow of time
From what I understand, entropy is a concept defined by the experimentalist due to his ignorance of the exact microstate of a system. To say the number of accessible microstates $W$ of the universe is ...
3
votes
3answers
90 views
Intuition behind the formula for macroscopic entropy
Wikipedia says that the 'macroscopic' definition of entropy is:
$$ \Delta S = \displaystyle \int \dfrac{dQ_{\rm rev}}{T}$$
Where $T$ is the uniform absolute temperature of a closed system and ...
5
votes
2answers
107 views
Casimir effect as an entropic force
When I first learned about the depletion interaction, my initial reaction was that it looks very similar to the Casimir effect. On making this remark to the professor, he replied somewhat mystically: ...
7
votes
2answers
132 views
Entropy of the Sun
Is it possible to measure or calculate the total entropy of the Sun?
Assuming it changes over time, what are its current first and second derivatives w.r.t. time?
What is our prediction on its ...
1
vote
0answers
41 views
Is there a known generalization of the Schmidt decomposition based on a maximal set of “locally recorded branches”?
I came across an unusual multi-partite generalization of the Schmidt decomposition in my work, which I describe below. Usually, when people say "a multi-partite Schmidt decomposition", they mean a ...
0
votes
1answer
59 views
Calculating the ideal mixing entropy using Gibbs' entropy formula
Two distinguishable gases are in separate volumes $xV$ and $(1-x)V$ $(x\in [0,1])$ respectively, and the number of particles on each side is $xN$ and $(1-x)N$ respectively. The volumes are separated ...
3
votes
1answer
43 views
Why do organisms accumulate potential energy?
I can understand that animals need some battaries to run. But, we learn that plants serve like batteries for animals because they accumulate the sun energy in the first place! You can eat them or burn ...
3
votes
1answer
84 views
Should entropy have units and temperature in terms of energy? [duplicate]
I've been thinking about entropy for a while and why it is a confusing concept and many references are filled with varying descriptions of something that is a statistical probability (arrows of time, ...
4
votes
1answer
56 views
Local decoherence and entropy
Consider a quantum system consisting of two subsystems, $A$ and $B$. Let $\rho$ be the density matrix of the whole system $A\cup B$. Let $|\alpha\rangle$, $\alpha = 1,2\cdots d_B$, be the states of ...
3
votes
2answers
179 views
The statistical nature of the 2nd Law of Thermodynamics
Ok, so entropy increases... This is supposed to be an absolute statement about entropy. But then someone imagines a box with a 10 particle gas, and finds that every now and then all particles are in ...
0
votes
0answers
41 views
Which pressure to use in the $T~ds$ equation?
Let's say I have an adiabatic, rigid, open container that has an amount of air at some pressure, $P_\text{cv}$, and some temperature, $T_\text{cv}$. I have heated pressurized air coming into the ...
2
votes
3answers
90 views
Shouldn't the sign of generated entropy always be positive?
I have a process where 10 g of liquid lead at 400 C is dropped into a water bath that is at 25 C. The lead solidifies over time and comes to thermal equilibrium with the water bath. The bath is so ...
0
votes
0answers
40 views
What is Verlinde's statistical description of gravity as an entropic force? [duplicate]
What is Verlinde's statistical description of gravity as an entropic force leads to the correct inverse square distance law of attraction between classical bodies?
0
votes
0answers
27 views
Finding a paper about error analysis in DNA sequencing in solid state nanopores using entropy meta-heuristics
I attended a talk at the APS March Meeting in Baltimore with the following abstract:
http://meetings.aps.org/Meeting/MAR13/Event/186412
I have been trying to find a paper that covers the topic of ...
1
vote
1answer
134 views
Why do humans like to break the second law of thermodynamics? [closed]
Roughly speaking, Entropy is a measure of the disorder of a system. However as humans, we tend to do the complete opposite. For instance, in a home if a painting that is hanging on the wall is ...
2
votes
0answers
43 views
Mathematical form of chemical potential difference and entropy production
I'm trying to understand the form of the 'force' which drives chemical reactions, ie. the difference in chemical potential, also sometimes called the 'affinity'.
$$\Delta \mu = - kT ln ...
0
votes
1answer
59 views
What is physics behind States of matter?
States of matter in physics are the distinct forms that different phases of matter take on. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma.
What is physics ...
8
votes
5answers
344 views
Perpetual motion machine of the second kind possible in nano technology?
First of all sorry for my English - it is not my native language.
During my engineering studies at the university the thermodynamics professor told us that the "second law of thermodynamics is not ...
0
votes
0answers
111 views
What is Mathematical formulation of entropic Gravitational force?
There are people proposing the possibility of using entropic force to explain the gravity force between objects.
The emphasis is that entropy is more fundamental than energy.
It is the closest study ...
4
votes
2answers
78 views
Time travel and entropy
I saw a post on reddit regarding immortality and how it would never be possible due to entropy. That said, assuming time travel was possible, would it not be possible to never reach this state of ...
3
votes
3answers
93 views
Entropy and Information
Several posts and my classes in thermodynamics equate increase in entropy with loss of information. Shannon clearly showed that the information content of a message is zero when its entropy is zero ...
0
votes
0answers
45 views
Bekenstein bound and the early universe [duplicate]
From what I understand, in the very early stages, the universe was extremely small. Also black holes are maximum entropy objects and thus saturate the bound.
Now what I don't get is that unless
...
0
votes
4answers
219 views
Has anyone ever tried to formulate physics base on computer science or Information processing?
Some physicists and university researchers say it's possible to test the theory that our entire universe exists inside a computer simulation, like in the 1999 film "The Matrix." In 2003, University ...
1
vote
1answer
46 views
Explanation Needed: Thermodynamics of a hot/cold water jet machine
I didn't know where to begin with this problem. I eventually found a solution online, which is why I'm reposting this question with an answer. I was wondering if anyone can explain the one question I ...
7
votes
2answers
179 views
Information Preservation and Burning Books
I recently read an article in the NY Times called A Black Hole Mystery Wrapped in a Firewall Paradox. I really liked the article, but reading one quote immediately made me think of asking Physics.SE a ...
3
votes
0answers
75 views
What is the entropy of a string?
In his The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics (p. 373) Susskind states that
the entropy of a string is [...] proportional to its length. ...
1
vote
1answer
46 views
How does one extract the universal part of entanglement entropy?
I want to know how equation 2.11 (page 9) follows from 2.10 (page 8) in this paper.
The two references mentioned just before 2.11 also seem to skip this crucial step. Unless I am missing something ...
4
votes
1answer
93 views
When is entanglement entropy the same as free energy?
I am given the feeling that there exists scenarios when this equality holds.
Can anyone state/refer to the situations?
One case that I hear of is that for $2+1$ CFTs the entanglement entropy ...
2
votes
1answer
79 views
Deriving entanglement entropy from Renyi entropy
My questions are based on this paper - http://arxiv.org/abs/0905.4013
Firstly I want to know as to whether some assumptions are needed about the relationship between the systems $A$ and $B$ for the ...
