Questions tagged [thermodynamics]

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using tag: [statistical-mechanics].

Filter by
Sorted by
Tagged with
-1 votes
0 answers
26 views

Can we calculate the average time a photon is "held" by a black hole?

I have a thought experiment. Imagine the Universe is made only of photons. We know we can add one "bit" of information to a black hole if it absorbs a photon whose wavelength is the same as ...
  • 6,336
0 votes
1 answer
32 views

Since water can evaporate at any temperature above absolute 0, would the water cycle still be possible even without the Sun?

Since water can evaporate at any temperature (or even sublimate at less than 0°C, although at a very low rate: Why does water not evaporate in below 0 degrees?), could there be a water cycle if there ...
  • 928
3 votes
1 answer
56 views

Relation between entropy and information

Lack of information is entropy. But entropy has dimension and information has no dimension. Then how do we relate these two terms..
  • 365
1 vote
0 answers
25 views

Poincaré Recurrence Theorem and the 2º Law of Thermodynamics [duplicate]

I am currently working on a 15 pages project about ergodicity and I wanted to include some discussion about the Poincaré Recurrence Theorem (PRT) and, as far as I know, it contradicts the 2° Law of ...
1 vote
0 answers
26 views

How to find temperature of primary plasma in million years after big bang?

For early times before light transparency and for ultrarelativistic domination I can write clearly, considering all degrees of freedom and coefficients: $$\rho\sim kT^4;\quad H=1/2t;\quad \rho=cH^2\...
1 vote
0 answers
16 views

Enthalpy of fusion - water [closed]

Trying to solve: $$l = \frac{Q(\text{melt})}{m(\text{ice})}$$ $$Q(\text{melting of water}) = Q(\text{heating of ice}) - Q(\text{cooling of water})$$ $$l \times m(\text{ice}) = c \times m(\text{...
2 votes
1 answer
75 views

Maximum information transmission rate using an electrical wire

Suppose that we're trying to transmit information at a distance $ L $ using an electrical wire made out of a material with known properties. The circuit setup is as follows: there's a wire that's ...
  • 491
3 votes
0 answers
29 views

What is the temperature at the center of a square plate subjected to 4 different temperature at each edge? [closed]

Dear all, assuming temperatures have all reached steady-state, is the center temperature will be exactly (T1+T2+T3+T4)/4 assuming this is a square plate with 4 different temperature at each edge?
1 vote
1 answer
29 views

Clarifying volume symbol notation with a slash through it

I am reading Munson's book on Fluid Dynamics. One thing I found confusing was this notation in the image below, where the Volume has a slash or strikethrough through it. I am not clear about the ...
  • 169
0 votes
0 answers
23 views

Optical Isolator Violation of Second Law of Thermodynamics

Okay, so I feel like I'm probably missing something obvious, but I will ask my question anyway (pardon my ignorance). I've been reading recently about optical isolators, and have read articles ...
  • 1
0 votes
1 answer
32 views

Gravity train in other planets?

A Gravity train (https://en.wikipedia.org/wiki/Gravity_train) goes through a tunnel inside a planet that connects point A with point B. On Earth, the train would not gain enough impulse to reach the ...
  • 928
0 votes
0 answers
6 views

Thermal Expansion of Two substrates/layers/materials [closed]

The Part Displacement Equation for Thermal Expansion Study is Now, if we apply this equation to a random example, we get: ΔL = (1.8 * 10 -5 K -1)(100°C - 25°C)(50.8mm) = 0.068 m However, what do you ...
1 vote
1 answer
22 views

What does volume parameter for a real gas equation mean for a fluid flowing in a pipe?

I want to understand what the volume means in a $(p,v,T)=0 \ $, for a system of real gases flowing in a pipe. Will it be that since the fluid is flowing, $V$, will be the local volume in a given ...
  • 33
3 votes
1 answer
135 views

Book recommendation for blackhole thermodynamics?

So I was reading this wonderful article about blackhole thermodynamics. https://hapax.github.io/physics/teaching/bh-thermo/ Can someone recommend a book which covers all 4 laws of blackhole ...
0 votes
0 answers
22 views

How can the internal energy of a system at fixed entropy and volume change? [duplicate]

I'm reading Blundell's Thermal concepts in physics and on page 169 he explains that the different thermodynamic potentials are actually the same quantity, the change in which will take on different ...
  • 523
2 votes
2 answers
32 views

What is the coefficient of thermal expansion of real gases in terms of temperature and pressure

Is there an equation for the coefficient of thermal expansion of real gases. If there is, what is it then? because I tried to use Peng Robinson equation of state, by substituting it's equation in ...
  • 33
2 votes
2 answers
125 views

Why does a photon with wavelength equal to the radius of the blackhole it's falling into have 1 bit of information?

In this lecture: https://www.youtube.com/watch?v=yMRYZMv0jRE&t=1260s Susskind derives the entropy of a black hole by assuming a bit of information could be added by a photon with wavelength equal ...
  • 197
1 vote
1 answer
32 views

Relation between time it take to diffuse and temperature

I was reading Reif's Statistical physics. In problem 7 in chapter 2, It says "Consider a thin copper wire stretched out along the $x$-axis. A few of the copper atoms, located near $x=0$, are ...
0 votes
0 answers
34 views

What are Applications of Thermodynamics in Real Life? [closed]

I am looking for some interesting applications of thermodynamics, in real life, that involves not only some text and formulae, but some interesting calculations.
  • 37
0 votes
1 answer
34 views

Would superconductors made from heavy radio-isotopes transition at higher temperatures?

I read somewhere that heavier variants of water (using deuterium or hydrogen) melt at higher temperatures compared to normal water. A simple argument for why this is could be the following: heavier ...
0 votes
1 answer
45 views

How does the density of the air affect our perception of temperature?

The classic experiment where you have someone put one hand in a bowl of hot water and the other in a bowl of cold for a while then move their hands to a warm bowl is a classic demonstration that our ...
  • 21.3k
1 vote
1 answer
30 views

Can trains use permanent magnets to be propelled?

Can a train (e.g. like a maglev train) use a set of permanent magnets (not electromagnets) that somehow can be propelled and maintain at least a constant speed with them? Is this an example of such ...
  • 928
5 votes
5 answers
931 views

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 ...
  • 642
0 votes
0 answers
18 views

How do I calculate the albedo of planets at different energy wavelengths? [closed]

So, I was given this question for a task: Find the surface albedo of each planet (Venus, Earth, Mars) where the reflected energy and emitted energy from the planet's surface are equal at λ = 5μ𝑚 and ...
  • 1
0 votes
1 answer
37 views

Why does sound travel faster while light travels slower in hotter mediums?

Sound travels at its slowest speed in a vacuum. Once it enters hotter mediums, it travels faster. On the other hand, light travels the fastest in a vacuum. Once it enters other mediums, it travels ...
  • 59
0 votes
0 answers
42 views

How do units work? [closed]

If an ice sheet at 0 degrees Celsius is being exposed to a heat source from the Earth, which is x watts/m^2 for 1 year, then the thickness, d, of the ice sheet melted would be $$ x = pdL $$ where $p$ ...
2 votes
1 answer
62 views

Name for a certain 1D lattice model

I have encountered a physical system where the microstates are described by a vector $$k = \left[k_1, k_2, \ldots, k_n\right]$$ where all the $k_i$ are strictly positive integers smaller than some $k_{...
0 votes
1 answer
40 views

Quality of ideal Gas approximation?

I know that modeling gases as ideal gases includes two approximations: approximating Particles as points regarding the collisions with macroscopic objects neglecting inter-particle interactions The ...
  • 103
0 votes
0 answers
35 views

I found an error in thermodynamics book. Am I? What should I do? [closed]

problem number 14 $w=vi \Delta t $= 11012860*10 = 792 000 J = 792 kJ so B must be a correct answer. I found an error in thermodynamics book. Am I? What should I do? Is it normal?
  • 45
0 votes
1 answer
51 views

Energy increasing with spacetime expansion?

Usually it is said that the density of dark energy/vacuum energy remains constant as spacetime expands, so the total amount of them is increasing. However, are there any examples of more "...
  • 928
0 votes
2 answers
67 views

Regular vs differential form of Fourier's law?

I was watching some of Michel Van Bizen's lectures on youtube, (Heat Transfer, video 16-18) and the guy mentioned that if a pipe or rather a bar was connecting a heat source and a cold source, we ...
1 vote
0 answers
20 views

Heat release from a uncoated vs coated titanium [closed]

Is heat released quicker in a titanium (uncoated) metal or titanium with silicone coating?
  • 111
0 votes
0 answers
18 views

Number of phases at the boundarys of phases diagram - supercritical boundary [closed]

how many phases are there at the orange and blue point on the boundary of the supercritical phase. i am inclined to say 0 but i am unsure, 1.1 because at the purple we have 2 phase, ex. in a ...
1 vote
1 answer
36 views

Use of Lagrange multipliers in derivation of the Bose-Einstein distribution

My main question in regards to this is an explanation on why/how you can use Lagrange multipliers when you have a function of infinite variables, what is the justification behind this? So to derive ...
0 votes
1 answer
49 views

Is it safe to say that temperature is a measure of molecular activity?

In Wikipedia Temperature is a physical quantity that expresses the hotness of matter or radiation. There are three types of temperature scale: those, such as the SI scale, that are defined in terms of ...
  • 45
-1 votes
1 answer
80 views

Is enthalpy relevant to aerodynamics?

Is the consideration of enthalpy relevant in the study of aerodynamics of aircraft wings and yacht sails, i.e. in (dry) air at wind speeds of 0 to 300 kts, in temps of 0 to 25°C in the normal ...
0 votes
0 answers
44 views

Does entropy change with the frequency of a system

Entropy is an important term and its definition varying from disorder to waste of energy to limiting factor of conversion of energy and work done can be given in term of entropy and tempetature. But ...
0 votes
2 answers
28 views

How does the adiabatic coefficient $γ$ vary with temperature (200K-20000K)? [closed]

At high temperatures, such as those encountered in hypersonic flight, γ varies a lot. My problem is that I can‘t find a graph accompanied by an explanation as to how & why it changes under ...
2 votes
1 answer
35 views

What's the most efficient way of keeping water hot? [closed]

Given a house with a large hot water tank of several cubic meters that is warmed by two wood burning boilers, I'm trying to figure out what is the best strategy to keep the water hot using the least ...
0 votes
0 answers
24 views

Power To Compress Ideal Gas In A Piston

I am familiar with isothermal and adiabatic ideal gas compression problems where a force is exerted on a piston of area A to move it some displacement in order to calculate work done. However I am ...
0 votes
3 answers
74 views

Question regarding Heat transfer in Carnot Engine

A Carnot Engine is a theoretical engine unlike a Sterling Engine which can be made practically. Some of the drawbacks of Carnot Engine are, 1)The Heat Transfer occurs only during isothermal process(...
0 votes
2 answers
14 views

How do you find the rate of heat flow through a multilayered wall? [duplicate]

Let's say that there is a wall, one side 20 C, the other 0 C. In between, there are 3 layers. One of copper, iron, and steel (hypothetical). The wall would look like this: 20 - Copper - Iron - Steel - ...
10 votes
1 answer
1k views

Do all solids sublimate at low enough temperature and pressure?

When we look at the phase diagram of a material, at low enough temperature and pressure, it tends to sublimate: So can it be true that no matter how strong a solid is, if at a low enough temperature, ...
  • 552
0 votes
3 answers
41 views

Why is the rate of heat transfer constant throughout different materials?

A video I watched recently mentioned how if there was a system, let's say, a bar connecting a hot reservoir to a cold reservoir, 100 - copper - iron - 0, the rate of heat transfer between the hot ...
2 votes
4 answers
97 views

Work in thermodynamics and work in mechanics

work in mechanics $w=\vec{f} \cdot \vec{s}$ work in thermodynamics $w=-p \Delta v$ I don't understand why $ \vec{f} \cdot \vec{s}= -p \Delta v$ ?
  • 45
0 votes
2 answers
44 views

How can flow devices be analyzed by choosing a closed system, i.e. a fixed quantity of matter?

I was reading Fundamentals of Engineering Thermodynamics by Moran and others and in the discussion of open and closed systems I found this - In subsequent sections of this book, we perform ...
1 vote
1 answer
33 views

Ohm and Fourier's law with Seebeck effect - derivation?

In my work, I am dealing with a mathematical model which involves thermoelectric magnetohydrodynamics (TEMHD). Ohm's law becomes modified to become $$ \mathbf{J}=\sigma\left(\mathbf{E}+\mathbf{u}\...
  • 11
2 votes
1 answer
45 views

Does pressure decay exponentially for a mixture of gases?

According to this answer, the partial pressure of a gas decreases exponentially in height, when placed in gravity. For a mixture of gases, the partial pressures of each component follows this law ...
0 votes
0 answers
24 views

Explanation of heat produced on friction [duplicate]

Assume you are holding a infiniteley long iron plate(taken metal because its good conductor of heat)in your hand You start moving your hand with start to move with a initial velocity on the iron plate ...
0 votes
1 answer
61 views

Explanation of Heat formed by friction

Assume you are holding a infiniteley long iron plate(taken metal because its good conductor of heat)in your hand You start moving your hand with constant velocity on the iron plate then in plate frame ...

1
2 3 4 5
262