2
votes
0answers
21 views

Is there a true parallel between Gibbs' phase rule and Euler's polyhedral formula?

Gibbs' phase rule states: $$F=C-P+2$$ where $F$ is number of degrees of freedom, $C$ is number of components, $P$ is number of phases. Euler's polyhedral formula states: $$V+F-E=2$$ where $V$ is ...
1
vote
1answer
22 views

Free Energy, Avialable Work in a reversible process

I was reading the Wikipedia page on Helmoltz Free Energy, http://en.wikipedia.org/wiki/Helmholtz_free_energy, and run across a point I cannot unravel. The discussion goes as follows, I reproduce it ...
1
vote
1answer
37 views

What is the difference between mechanical and thermodynamic pressure?

To start with I know thermodynamics deals with processes at equilibrium. Hence the thermodynamic pressure should most likely be the pressure of a fluid at equilibrium. I'm not sure if a fluid flow ...
0
votes
0answers
12 views

Calculating temperature raise from specyfic heat and energy [on hold]

Im trying to calculate/estimate temperature change of 200g copper device (large shunt resistor) and I'm afraid that I've done something wrong. Here is my data: I = 600 [A] // nominal maximum current ...
-1
votes
0answers
18 views

Thermodynamics Assignment: Combustion [on hold]

Acetylene, Methane and Octane are burnt in air (75% Nitrogen, 25% Oxygen) and forms Carbon Dioxide, Carbon Monoxide, Nitrogen and Water This is the unbalanced equation: C2H2 + CH4 + C8H18 + O2 + N2 ...
6
votes
1answer
100 views

Why doesn't gravity ruin satellites?

Recently I watched a documentary about Io, a moon around Jupiter. Io has volcanic activity even though it is small and can't retain heat well because gravity from Jupiter and a nearby moon cause it to ...
-2
votes
0answers
31 views

Thermodynamic Processes [on hold]

can someone help me in these problems? -An isentropic process occurs at a constant entropy,what is a "entropy"?(what mean)? -An isenthalpic process introduces no change in enthalpy in the ...
4
votes
2answers
40 views

Why is adiabatic process isentropic?

I have read that adiabatic process is isentropic because there is no heat exchange in an adiabatic process and thus no change in entropy. But my question is - Even in adiabatic process, work can be ...
-1
votes
1answer
36 views

Boundary conditions for the heat equation when solving a mass density gradient

I'm working with a mass density gradient with length $L$ and I'm trying to solve the heat equation in 1-D (mass diffusion equation, $\partial_t\rho(t,x)=D\Delta\rho(t,x)$), but I'm not sure which ...
1
vote
1answer
23 views

fusing two air containers with fixed pressures $p_1,p_2$ and temperatures $T_1, T_2$, what end-result $T$ and $p$ will be?

Let's say that I have two boxes with both volumes equal $V$, filled with an air. Air in first box have pressure $p_1$ and temperature $T_1$, likewise air in second box have pressure $p_2$ and ...
1
vote
2answers
26 views

Temperature in an isobaric process

I have a certain conceptual issue - I'm solving heat engine problems and I found something difficult to understand. Let's take an isobaric part of a cycle of an engine, let's say that the ideal gas is ...
2
votes
0answers
16 views

Director field fluctuations in a liquid crystal in a magnetic field

If we consider the Frank elastic free energy in the equal constants limit (for more details, see here Chapter 4.1.) with an external magnetic field, we have $$ F = \frac{1}{2}\int \text{d}^3 r\left ( ...
0
votes
2answers
62 views

What is the principle of equivalence in thermodynamics?

I've been searching for this for a while. There is a principle of equivalence in general relativity: http://en.wikipedia.org/wiki/Equivalence_principle But I need the principle of equivalence in ...
0
votes
1answer
28 views

How to use specific heats and temperature change in a system to calculate mass?

In a system where multiple liquids and solids are mixed together with different specific heats at different initial temperatures, reaching an equilibrium temperature, how do all of these things relate ...
0
votes
1answer
29 views

Latent heat of vaporization

The molecular weight of water is 18.015 gram. The number of moles of water in one liter (1000 gram) will be: $3.34\times 10^{25}$ molecules (in 1kg). We know that latent heat of vaporization of water ...
4
votes
2answers
65 views

Why does an electric motor burn up when you physically stop it?

As an electric motor spins, the energy from the electricity is 'conducted' to the rotor by the magnetic fields. However, when the motor is stopped, the energy becomes heat and burns up to motor. ...
1
vote
0answers
31 views

Radiation heat transfer

I'm looking at the radiosity equations for heat transfer http://en.wikipedia.org/wiki/Radiosity_(heat_transfer)#Radiosity_method Specifically, I'm hesitant to accept the equation: $$ \dot Q_i = ...
0
votes
1answer
35 views

If fans increase the heat of the air and this DIY AC decreases it, why don't they neutralize eachother?

Please try to answer in layman terms, i am only starting to study thermodynamics (And physics) In my book one of the curiosity parts gives that fans don't actually cool the room but by hitting the ...
2
votes
2answers
141 views

Does wrapping a wet paper towel around a glass bottle really speed up the cooling process?

There are claims like this one that you can improve the cooling speed of beverages when you put them wrapped in a wet paper towel inside the refrigerator/freezer. I've just tried it by myself and ...
0
votes
2answers
34 views

Heating a black body

By definition, Black body has absotivity=emmisstivity=1. This means the black body radiates all energy it accepts. Does this mean the black body cant be heated?
3
votes
0answers
48 views

How to solve the heat equation for compound materials with different heat conductivities numerically?

I'm solving the heat equation with time dependent boundary conditions numerically in a 2D system using the ADI scheme. For the purpose of this question, let's assume a constant heat conductivity and ...
4
votes
0answers
17 views

Time for which a drop stays in the leidenfrost point

Is there any way to find out the time required for a drop of given dimensions to vaporize after attaining Leidenfrost point?
2
votes
1answer
71 views

Thermodynamics, chaperones : How to model polymer fragmentation

Living polymers are well described by equilibrium statistical physics. Now I would like to consider a case were living polymers undergo fragmentation due to chaperones. I can think of a kinetic ...
0
votes
1answer
18 views

In what forms do fire energy transfer in common situations

Yesterday I was standing by the campfire. I used to think that campfire heat carried to me only by air. It was heating my face too much, so I blocked it with my hand just like blocking the sun. Then ...
3
votes
1answer
73 views

Thermodynamic relations

I'm asked to establish the following relations: $\left( \frac{\partial C_V}{\partial V} \right)_{T,N} = \frac{T}{N} \left( \frac{\partial^2 P}{\partial T^2} \right)_{V,N} $ $\left( \frac{\partial ...
0
votes
1answer
36 views

Coefficient of expansion [closed]

At a temperature of 21.80°C the hole in a steel plate has a diameter of 1.040 cm. If a steel rod with a diameter of 1.049 cm has to just slip through this hole, to what temperature should the plate be ...
2
votes
0answers
56 views

Quantum Fourier Transform and Entropy

QFT is a nonlocal unitary transformation and so can generate entanglement in a system. It means a separable pure state can be converted into an entangled pure state. Now since the presence of ...
1
vote
0answers
46 views

Could water physically makeup the core of a planet or otherwise large celestial mass?

Knowing very little about the nature of water, wondering how it might behave at the centre of a planet or centre of an another massive gravitational body. Could water take such pressures or might it ...
0
votes
2answers
58 views

Energy Analysis of Niagara Falls in Linus Pauling's “General Chemistry”

I just started reading Linus Pauling's "General Chemistry" and the first example confuses me. He writes: Example 1-1. Niagara Falls (Horseshoe) is 160 feet high. How much warmer is the water at ...
0
votes
2answers
35 views

Is there an analogue to the role of vapor in liquids and gases, but for solids and liquids?

It seems common for an ordered phase to have some amount of disorder present. For example, the average moment of a ferromagnet is less than maximum except at T=0 due to the presence of fluctuations. ...
0
votes
1answer
30 views

How to increase temperature of small mass using large mass of lesser temperature?

I know that heat flow from higher temperature to lower temperature, but theoretically, is it possible to build heat pump that can move energy from ocean which are at ~295 kelvin to a small boiler ...
2
votes
0answers
63 views

Why is the Bekenstein Bound an equality for Black Holes?

The Bekenstein bound is a limit to the amount of entropy a thermodynamical system can have. The bound is given by the following expression: \begin{equation} S \leq \frac{2 \pi k R E}{\hbar c} ...
0
votes
2answers
35 views

How much electricity can be produced by my thermoelectric generator?

I am using a thermoelectric cooler from a pc's heatsink to produce electricity. Its size is 30mm by 30mm. I will cool it on one side at -10 degree Celsius and the other at 24 degree Celsius. Can ...
0
votes
1answer
44 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
23 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
51 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
23 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
28 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
51 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 ...
7
votes
1answer
466 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
100 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
71 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
1answer
20 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
21 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 ...
0
votes
0answers
33 views

Thermodynamics First Law Question - Expansions

Two thermally iso- lated cylinders, A and B, of equal volume, both equipped with pistons, are connected by a valve. Initially A has its piston fully withdrawn and contains a monatomic gas at ...
8
votes
5answers
98 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
37 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
5answers
115 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
19 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
32 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 ...