Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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].

0
votes
0answers
17 views

Difference between diffusion and interface mobility?

I have had this question when reading about the growth of ferrite (in steel) that is controlled by carbon diffusion and by interface mobility of Carbon. I would like to know the difference between ...
0
votes
0answers
33 views

Does thermal equilibration affect compression work for an ideal gas?

Consider compression of an ideal gas that is uniform in pressure but nonuniform in temperature, from volume $V_1$ to $V_2$. For simplicity of the problem let's say the gas is divided into 2 regions $A$...
1
vote
0answers
28 views

Classical chaos at finite temperature

Is there any finite temperature generalization of classical chaos? In quantum chaos, at least with regards to out-of-time-order correlators, the generalization is clear - one simply takes a thermal ...
0
votes
1answer
100 views

Partition Function of an Ideal Gas

Which is the correct partition function for an ideal (bosonic) gas at high $T$: 1) Sum over the number of particles in each momentum state: $$ z_{\vec{p}} = 1 + e^{- \varepsilon_{\vec{p}}/T} + ... = ...
-1
votes
1answer
65 views

What is Kirchoff's thermal radiation law? [closed]

Is Kirchhoff's law true even if body is not thermal equilibrium with surrounding. And according to Kirchhoff's law absorptivity is equal to the emissivity of body.
1
vote
2answers
43 views

How do we measured specific heat capacity without knowing heat or other material heat capacity?

How can we find specific heat capacity without using heat, $$ c= \dfrac{\delta Q}{m \,\delta T}$$ Calorimeter $$ c_1\cdot m_1\cdot \delta T_1 =c_2\cdot m_2 \cdot \delta T_2 $$ In this formula we can ...
-2
votes
1answer
95 views

QM explanation (electrons and lattice structure) why aluminum does not get hot in an oven?

I have read this question: Why can I touch aluminum foil in the oven and not get burned? But the answers therein only explain on a classical level why aluminum foil being a very good conductor and ...
0
votes
1answer
25 views

Confusion of the Isobraic Process Heat equation

I was currently reading a wiki article on Isobaric Process (Link at bottom f post). And am confused as to why in there derivation of heat of a an isobaric system they use specific heat capacity for ...
1
vote
2answers
70 views

Violation of Stefan's law when shining a light on a black body

Suppose there is a black body in a dark room and the room temperature is constant. Now a ray a light is shone upon it. Since a black body absorbs all radiation that falls upon it, it must absorb more ...
0
votes
0answers
28 views

Partition function for a system of particles in a lattice

The problem A $d$ dimensional lattice system with $N$ sites is occupied by particles ($n_i$ particles at site $i$) and has the following hamiltonian $$ H = \sum_{i=1}^N \log{(1+n_i)} $$ I have to ...
0
votes
0answers
32 views

How long does it take a gas to equilibrate with a container's temperature?

Initial Conditions in a vessel: P~my unknown, but ~100torr, V=5000cc, T=35C, gas is 50/50 N2/He Laser drill a hole in the initial volume of diameter=10mils through a chamber wall thickness of 0.75mm. ...
3
votes
1answer
98 views

Two definitions of a macrostate

I fully understand the concept of a microstate, but I'm having some trouble reconciling two seemingly contradictory definitions of a macrostate. Here are the two definitions: A macrostate is defined ...
3
votes
1answer
69 views

Physical significance of free energy in canonical ensemble?

From macroscopic thermodynamics I understand that the free energy equals the total energy of the system minus the energy it would have cost a thermal reservoir to create it. So any energy in "excess" ...
1
vote
0answers
32 views

Will magnifying light make it more powerful? [duplicate]

I know there is a physics law that says a light magnification can't be more hot than the light source itself, but can it be brighter at the least?
3
votes
0answers
68 views

Meaning of zero temperature in terms of $1/T=\partial S/\partial E$

Suppose we have a $NVE$ system of a pure crystal. From the definition of the temperature in macroscopic thermodynamics, $$\frac{1}{T}=\left. \frac{\partial S}{\partial E}\right |_{V,N}$$ . Then ...
0
votes
1answer
43 views

Heat conduction through wall - alternatives?

This is basically a physics question, though the motivation is DIY. There is a wood burning stove on one side of a wall in a room. It is used for cooking. It has an external air supply. On the ...
0
votes
1answer
31 views

Simulate cluster in a heat bath

I want to simulate a cluster in a heat bath. I always thought I had to simulate it first in the microcanonical ensemble (N,V,E) until I reach the equilibrium. In the equilibrium the temperature will ...
0
votes
1answer
32 views

Molar heat capacity of constant volume for an ideal gas under constant pressure?

I'm a bit confused by this. For an ideal gas under pressure of n moles. If some amount of energy is added Q and the temperature increases dT how do you find Cv ? Molar heat capacity for pressure i ...
2
votes
3answers
88 views

How does $dS \ge 0$ imply a system cannot receive more energy than work supplied?

I am reading a book that asserts the following: The second law arises from an equation of the form $$dS = \mu\,dE + \mu\,dW \tag{1}$$ where $dS$ is the change in entropy, $dE$ the change ...
1
vote
1answer
59 views

Einstein solid: one or three dimensional quantum harmonic oscillator?

The Einstein model for solids assumes all atoms vibrate with the same frequency $\omega$, each atom being modeled as a quantum harmonic oscillator. The thing is: solids are three-dimensional objects, ...
0
votes
2answers
53 views

Where in microwave ovens things warm faster?

I want my mug to boil as soon as possible and I prefer not to throw energy away. Where in microwave ovens things warm faster?
0
votes
1answer
43 views

What is a formal rigorous definition of a thermodynamic process?

What is a formal rigorous definition of a thermodynamic process? I went across few references but have not found out a strict formal definition of thermodynamic process. So any discussion regarding ...
22
votes
4answers
7k views

Why is the Sun approximated as a black body at ~ 5800 K?

Apparently spectral solar radiation is approximated by a black body at 5800 K. The spectral black body distribution (Planck distribution) is shown below (from Incropera, Fundamentals of Heat and Mass ...
3
votes
1answer
58 views

Could someone explain what it means that temperature is a lagrange multiplier of energy? [duplicate]

I have looked online but I couldn't find anything that explains this definition
0
votes
1answer
28 views

Equation for simultaneous cooling and conduction

Imagine a long, uniform metal rod placed on the positive $x$-axis being heated with a power $P$ from its end at $x=0$. It is cylindrical in shape and the cross-section is a circle of radius $r$. ...
0
votes
2answers
41 views

Could light and heat reflecting off of surface ice on Earth have a noticeable impact on the sun?

If so, what could be the impact of these reflections on the sun during an ice age on Earth?
-7
votes
1answer
86 views

Could micro-states not have equal probability as assumed? [closed]

How could micro-states have uniform distribution in a 3D space unless there was 0 Gravity? Gravity violates the assumption of equal probability as it makes matter move in a predictable direction. ...
2
votes
3answers
111 views

How does flow work arises in enegy balance using Reynolds Transport theorem?

I will use the below mentioned form of Reynolds Transport theorem(usually derived in Fluid Mechanics context) to give a relation between a Control mass system(no mass in or out) and Control Volume(...
0
votes
0answers
33 views

How come we can treat space as a blackbody?

I thought that the condition to be a black body was that an object had to absorb all incident radiation without reflecting any. My understanding is, electrons in atoms absorb the incoming radiation. ...
0
votes
0answers
24 views

Rayleigh-Benard convection criterion

So, every text starts with a uniform heating of the bottom plate of a horizontal fluid for Rayleigh-Benard (RB) convection. Is "uniform heating" and "horizontal plate" an essential starting point? If ...
0
votes
0answers
31 views

In the Joule-Thomson experiment, how is $T_1-T_2$ determined?

I figured out that $H = U +pV$ is constant in this adiabatic condition. I am confused about the expression "$T_1-T_2$ is determined in this condition". I don't think it's an ideal gas, so $\delta(H) \...
1
vote
2answers
54 views

Can Mars have an oxygen atmosphere?

It is my understanding that, in its gaseous state, oxygen molecules move fast enough to achieve escape velocity. On Earth, we see this more clearly with helium. Regardless of what's happening on ...
0
votes
1answer
25 views

Thermal radiations

everything having temperature above 0 k emits radiation. But those radiations depend upon temperature of the body and not on nature of the body. Why thermal radiations are not material dependent?
3
votes
1answer
126 views

Is it possible to find dry ice crystals lying around the base in Antarctica?

Dry ice sublimates at -78.5°C, while the lowest temperature registered is about -89.2°C around the Vostok station in Antarctica. Imagine a person living on that station on that day (or night, since it ...
0
votes
0answers
27 views

How much conduction, radiation and convection influence in a thermos flask?

It has been thoroughly repeated that thermos flasks prevent heat loss by minimizing heat conduction, radiation and convection from the bottle to its ambient. This has been answered in this SE. However,...
0
votes
0answers
52 views

Assumptions and limitations for ideal gas

Assumption: In the assumption for ideal gas law, it is stated:"The time it takes to collide is negligible compared with the time between collisions." For, this assumption, can i just say there is only ...
0
votes
1answer
21 views

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 ...
2
votes
0answers
30 views

As the universe expands, ultimately, will it continue to reach closer and closer, to absolute zero but never get there?

First law of thermodynamics, the conservation of energy, doesn't this law all but guarantee that regardless of how far the universe expands it will forever contain its original amount of energy? All ...
1
vote
1answer
33 views

How to calculate the change of heat between metal heater and air?

I have a basic system, let's say a cube of air of size $1m \times 1m \times 1m$. I place a metal heater next to it, for simplicity its size will be $0.1m \times 0.1m \times 0.1m$ (so the contact area ...
-2
votes
2answers
75 views

Is anything wrong with the given statement? [closed]

If we take randomly any two bodies, the one with the higher temperature will contain more heat.
4
votes
1answer
92 views

Where do the air bubbles inside the pool come from?

Here's a pic of my legs in the pool water. There are tiny air bubbles on them. I thought this is the result of air coming out of my leg, but I learnt that this is not the case. Also, there seem to be ...
1
vote
0answers
39 views

Why does a cooking thermometer show different temperatures when touching the container of a liquid?

I have a cooking thermometer that looks like a 10-15 cm long metal rod, that can be inserted into the thing you want to measure the temperature of: When inserted into boiling water, I observed that ...
0
votes
2answers
40 views

Contradiction in pressure exerted by compressed gas

For the pressure exerted by compressed gas, its stated in my textbook: "The result is that at high pressures the molecules of a gas are so compressed that their volume becomes a significant fraction ...
1
vote
1answer
83 views

Is 1 liter always equal to 1 cubic decimeter, independently of temperature, pressure, etc?

I recently found this conversion table for the unit conversion $\rm mmol/m^3 \ \leftrightarrow\ \rm mmol/L$ (millimoles per cubic meter to millimoles per liter) My physics is very rusty, but just to ...
-1
votes
1answer
24 views

How many degrees Celsius/Fahrenheit can be reached in 1 square meter area using magnifying glasses?

The magnifying glasses are each 10 meters in diameter, their collected light is concentrated via mirrors into a 1 square meter spot. Is it possible to get a temperature higher than 2000 degrees ...
0
votes
1answer
27 views

Monte Carlo importance sampling in statistical physics finite approximation question

I am trying to understand a formula found in "Topics in Current Physics: Monte Carlo Methods in Statistical Physics Springer-Verlag" attributed to L. D. Fosdick methods comp physics 1963. I can't get ...
0
votes
1answer
39 views

What process is it when the polytropic index $n$ is equal to $- \infty$?

From $$Pv^n = \mathrm{constant}$$ When $n = - \infty$ What kind of process is it.... Eg... When $n= \infty$, It is constant volume.... Therefore when $n =- \infty$... What is constant?
1
vote
0answers
40 views

Heat transfer on Mars

SCENARIO: I have been tasked with finding the heat transfer across a composite wall on Mars. On the left of the wall there is air maintained at Earth atmospheric conditions and room temperature (101 ...
2
votes
4answers
99 views

Why does energy flow downhill/entropy increase?

I'm not sure if this is asked anywhere else before, but so far my search isn't fruitful. I'm in my second bachelor of physics and mathematics, and currently taking a thermodynamics course. We just ...
0
votes
1answer
42 views

When we burn a wood it burns with flame although it do not contain any gaseous substance [duplicate]

In books it is given that flame is only produced when gaseous substance burn but when dry wood is burnt it also burn with flame.why.