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

learn more… | top users | synonyms (1)

0
votes
1answer
273 views

Time to heat/cool a room

So, I have a basic, very basic, understanding of thermodynamics. I don't take it until next semester. I'm attempting to write a program which plots a temperature over time graph of a room being ...
0
votes
0answers
38 views

Natural refrigeration

I have an electricity-free pot-in-pot refrigerator that uses evaporative cooling to keep the inside cool. However, I live in a very humid place, so the rate of evaporation will be low and hence this ...
1
vote
2answers
2k views

Heat transfer and temperature difference of 2 liquids

We know that heat transfer is calculated by equation $Q$=$m$×$C_p$×$\Delta$$T$. Let's perform 2 experiments- Imagine I have 2 cups with water with same masses(volume). 1 is at 100 degree C and other ...
0
votes
1answer
123 views

Which thermoelectric effect is better?

I am doing an experiment which requires the thermoelectric effect. I know about the Seebeck and the Peltier effects. Well, from what I have found till now on these topics is that they both can produce ...
0
votes
0answers
36 views

Question regarding temperature as a property of a system

This is probably silly question but I got stuck while reading “Lectures on Theoretical Physics-Thermodynamics and Statistical Mechanics” by Sommerfeld. In the first chapter it says : Temperature ...
2
votes
0answers
80 views

Could CP violation be exploited to violate the second law?

I don't understand well CP-violation, but since it introduces a microscopic irreversible process, couldn't it be somehow exploited to decrease entropy? For instance, if we could somehow use it to bias ...
8
votes
1answer
535 views

Camp Fire Crackle

I was sitting around the camp fire and there was a periodic sound of cracking and pieces of the burning wood flew off. My question is what is the mechanism for the cracking of the wood? I was thinking ...
1
vote
4answers
505 views

Can a thermometer really measure the temperature of a substance?

When we measure the temperature of a substance by using a thermometer and waiting until the two come into thermal equilibrium, the thermometer will not display the original temperature of the ...
4
votes
1answer
84 views

A real gas with gravitation-like interaction

Consider a system (a gas) of point-like particles with a gravitation-like interaction (potential) $V(r) \sim \frac{1}{r}$ between pairs of them. One can rule out statistically that two particles will ...
0
votes
2answers
116 views

requirements for hydrogen fusion

What are the requirements for hydrogen atoms to go through fusion? Is it a ratio of heat to pressure or are there specific heat and pressure values that must be met (per atom or per mole?) Are there ...
1
vote
0answers
77 views

Restrained expansion of a piston/cylinder

Suppose an ideal gas in a piston cylinder has some initial pressure $p_1$, volume $V_1$, and temperature $T_1$. A pin, which holds the piston in place, is suddenly removed, and the gas quickly ...
8
votes
5answers
154 views

How can point-like particles in an ideal gas reach thermodynamical equilibrium?

Having learned that the particles of an ideal gas must be point-like (for the gas to be ideal) I wonder how they can reach thermodynamical equilibrium (by "partially" exchanging momentum and energy). ...
1
vote
0answers
331 views

VdW Gas Entropy/Enthalpy/Gibbs Free Energy of Mixing in 2 Chamber Experiment

What are the equations for $\Delta S_{mix}$, $\Delta G_{mix}$, and $\Delta H_{mix}$ for a real gas? Explanation: In one of the most well known experiments in thermodynamics, two chambers are ...
2
votes
4answers
264 views

What exactly is temperature in the Gibbs free energy?

In equation of Gibbs free energy change $(\Delta G) = (\Delta H)-T(\Delta S)$, is $T$ the system's or surrounding's temperature? Edit:Oh sorry I am not clear earlier now I get clear question.I know ...
0
votes
0answers
27 views

What is Fermi energy and Fermi level? [duplicate]

What is meant by Fermi level and Fermi energy? And what is the difference between the two?
1
vote
1answer
40 views

Fuel and heated iron?

If I have a pile full of fuel (gasoline) - and I also have heated iron ( very very hot - color orange) and I put the Iron in the pile , Would the gasoline will burn ? I mean - does gasoline need ...
0
votes
1answer
195 views

Carnot Engine Work from Heat Exchanger between Two Gas Streams

To be clear, this is not a homework question, but it is something I am studying for an exam. The question is about a hilsch tube which separates a stream of high pressure air to a high temperature ...
1
vote
2answers
148 views

What will happen to water at $0^\circ$ Celsius kept in large evacuated chamber

Suppose some water is kept at $0^\circ$, in a glass (ideal container, if necessary). Now it is placed in a large evacuated chamber. What will happen? I think some water will vaporize, some will ...
9
votes
2answers
295 views

Nonequilibrium thermodynamics in a Boltzmann picture

The Boltzman approach to statistical mechanics explains the fact that systems equilibriate by the idea that the equillibrium macrostate is associated with an overwhelming number of microstates, so ...
8
votes
3answers
747 views

Why must the particles of an ideal gas be point-like?

Why is a gas of elastically colliding hard balls of finite size not ideal? Respectively: Why is it essential that the particles of an ideal gas are point-like? Especially: Which ...
2
votes
2answers
234 views

System in mechanical but not thermal equilibrium

Let's say there are two systems which can interact by a moving wall but cannot exchange heat. Then the system will be in mechanical, but not necessarily in thermal equilibrium. The maximality of ...
2
votes
1answer
162 views

Immediately after the Big Bang, was the universe in a state of extremely low or extremely high entropy?

Phase space theory suggests that the largest course-graining region, $p$, in a phase space, $P$, is the point in the phase space with the highest entropy. As such, it is in thermal equilibrium with ...
6
votes
3answers
796 views

Why is the Gibbs Free Energy $F-HM$?

With magnetism, the Gibbs Free Energy is $F-HM$, where $F$ is the Helmholtz Free Energy, $H$ is the auxiliary magnetic field, and $M$ is magnetization. Why is this? Normally, in thermodynamics, we ...
0
votes
0answers
100 views

Adiabatic Expansion with expanding control volume

I have a tube with a length $L$ and diameter $d$ that is open on 1 side. At a certain point (say $x$) from the closed end of the tube, I have a gas with a high pressure. At this point, $x$, there is ...
-2
votes
1answer
135 views

Aerodynamics and thermodynamic [closed]

Why can we refer an object as being aerodynamic but we can't refer an object as being thermodynamic, and if an object is thermodynamic what does it even means?
0
votes
1answer
82 views

Ideal gas system with diathermic piston externally manipulated

I wanted to ask about the following problem: An ideal monatomic gas is separated into two volumes $V_{1}$ and $V_{2}$ through a diathermic piston, such that each volume containing $N$ atoms and the ...
15
votes
1answer
900 views

Why doesn't breath condense around poop of flies on the window's glass?

One day it was raining outside and I was breathing on the glass of my window. I noticed that around the spots of fly poop there is a circle where vapor does not condense. With time the circle becomes ...
2
votes
1answer
109 views

Enthalpy in thermodynamics!

What does enthalpy tell us about? According to definition; it is the total heat content of a system, if it is the total heat content of a system then what is Internal Energy? Since we know, ...
1
vote
2answers
93 views

EM Radiation and Heat

If there is EM radiation, will there always be a heat exchange between the wave and its surroundings? If you have an extremely energy-efficient light bulb that converts ALL the energy it receives into ...
2
votes
1answer
609 views

Specific heat of aluminium as a function of temperature

I am trying to find the curve describing the specific heat of aluminum as a function of temperature between about 50K to 300K(or room temperature) for an experiment I am doing. Ultimately I need to ...
9
votes
4answers
448 views

Can we detect whether food has previously been heated in a microwave oven?

An acquaintance told me that she refuses to eat microwaved food because she read that the microwave changes the molecules of the food somehow. Her statement is vague and her sources are dubious but I ...
2
votes
0answers
103 views

Lennard-Jones induced pseudo-molecules

It can be shown that the Lennard-Jones potential - which describes the interaction between particles in non-ideal gases - gives rise to pseudo-molecules: after a triple "collision" of three ...
3
votes
2answers
540 views

Can you extinguish a fire by cooling down the fuel?

I know that temperature plays a crucial role in the process of ignition, as most combustible materials will spontaneously start burning in presence of enough oxygen when heated above the kindling ...
3
votes
1answer
255 views

How do you explain the fact that when air expands freely into an evacuated chamber from a constant pressure atmosphere, its temperature increases?

I came across this paper: Baker, B. (1999). An easy to perform but often counterintuitive demonstration of gas expansion. American Journal of Physics, 67(8), 712-713. ...
4
votes
2answers
520 views

Physical significance of negative temperature

I read some answers regarding negative temperatures but I think my question is new. I want to know that what is the physical significance of negative temperature. Suppose I say a body has ...
2
votes
2answers
229 views

Heating effects of microwaves

I understand the heating effect(dielectric heating) of microwaves. This heating is caused by using a frequency of 2.45 GHz and this is the same frequency at which Bluetooth works and the L and S ...
1
vote
1answer
105 views

Definition of entropy

In my textbook there is written $$\Delta S = \int_R \frac{\delta Q}{T}$$ where the $R$ means calculated along a reversible transformation. The variation of entropy only depends upon the ...
0
votes
2answers
707 views

Why is the direction of a flame is always upward? [duplicate]

why a candle's flame direction is always upward? What is the coposition of fire? Don't say it's energy. There is something else.
7
votes
3answers
352 views

Why does ice melts, waits for 100 degrees and THEN vaporises? Why is not the process of expansion of things continuous?

What I am asking is this: Why can't a body be solid, then solid-ish, then solid-like, then liquid-like, then liquid-ish, then liquid, then vapor-like and then vapor? Why is there a rigid temperature ...
1
vote
1answer
612 views

Meaning of heat sink in engine analysis [closed]

I am confused with the meaning of sink. What part of vehicle engine acts as reservoir and what does as sink?
0
votes
1answer
156 views

Comparing unknown temperature scales [closed]

Source: Principles of Physics by Resnick, Halliday, Walker. $9^{th}$ edition. Chapter 18. Problem 6. On a linear $X$ temperature scale, water freezes at $-125.0^0X$ and boils at $360.0^0X$. On a ...
46
votes
5answers
12k views

Why does a candle blow out when we blow on it? Our breath is 16% oxygen and only 4% CO2

Don't say that a layer of carbon dioxide covers the flame, because our breath has more oxygen than carbon dioxide. Also, our breath does not cool the flame as it is itself warm. So what is happening ...
6
votes
1answer
143 views

Doubts about the ideal gas law

EDITED AND SOLUTION: In fact my stupid mistake was to take the wrong value for my $P_1$ and I was getting an 1.2998 that finally is a 1,9178 within just a difference about 7%. So at the end they are ...
1
vote
1answer
392 views

Understanding collision terms in Boltzmann equation

I am reading a paper that deals with the Boltzmann equation. They add a collision which is supposed to account for collisions which happen when particles are within a radius of $d$ from each other. ...
0
votes
0answers
52 views

Explain Heat Transfer

I would like to know what are these formulas used for. There is no intro about it in my book at all, and I am reading Heat Transfer book. If needed Q. can be edited.
1
vote
1answer
164 views

Does thermal energy include the kinetic energy of the electrons?

Or is the kinetic energy of the electrons not counted towards the thermal energy? (In other words only the energy of the lattice structure is counted)
2
votes
0answers
58 views

What's the connection between being homogeneous in energy and having a proper time scale?

Towards the end of page 8 of this scientific paper, I have found the following sentence: ...given the fact that the system is homogeneous in energy, or equivalently, that it has no proper time ...
0
votes
0answers
263 views

Determine pipe outlet temperature without length?

Let's say I am flowing a fluid through a pipe that has a constant surface temperature. Is it possible to determine the heat flux on the inner surface without knowing the pipe's length when the only ...
2
votes
2answers
115 views

Container divided in two parts with ideal gas

I wanted to ask your help with the following problem: Consider a closed container, that is, with insulated walls impervious, and rigid. The container is divided into two parts by a wall having the ...
0
votes
0answers
63 views

Applied / environmental question: direction of exhaust fumes

I'm not sure the Physics StackExchange is the perfect place for this environmental/applied physics question, but as I found no forum more fitting I ask my question here. Otherwise please move my ...