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 (3)

0
votes
2answers
60 views

If for an isolated system, $\Delta$U is 0, then what is $\Delta$S?

My textbook answers this question as $\Delta$S > 0 but I really don't know why. If system is isolated, then dQ = 0 i.e. S = 0. (S = dQ/T). I don't really get why question has provided an additional ...
2
votes
2answers
84 views

Does invariant mass depends of temperature? [duplicate]

From special relativity theorie we know that $E = mc^2$. When a system acquires energy, mass becomes greater. That is clear for kinetic energy, because we have a formula that gives m as a function of ...
2
votes
1answer
55 views

Is heat radiation an instance of electromagnetic radiation?

From school physics I recall the following means by which heat spreads out: conductance (particles bump against each other), radiation and the original heated mass moving (for example: sea currents). ...
1
vote
2answers
62 views

Internal energy, Enthalpy, and Heat

Setting a general background for my question: We know that the equation of state for an ideal gas is given by: $$pv=RT$$ where: $p$ is the absolute pressure of the gas. $v$ is the volume per ...
0
votes
0answers
14 views

Increase in temperature of metal piece during filing explain by the Gibb's equation?

When we file the metal the surface of the metal gets worn out in the form of small pieces of metal. The file acts as medium to transpher the energy from the body to the metal piece in the form of ...
0
votes
1answer
16 views
1
vote
2answers
80 views

Change in entropy of two isolated systems merged into one system

From Statistical Physics, 2nd Edition by F. Mandl: Two vessels contain the same number $N$ molecules of the same perfect gas. Initially the two vessels are isolated from each other, the gases ...
0
votes
1answer
47 views

Difference between throtling and adiabatic expansion

Throttling process is an isoenthalpic process.$$U+PV=constant.$$ during throttling process does the gas do work at the cost of internal energy such that its temperature decreases? Then what is the ...
1
vote
0answers
38 views

How to understand better this point of view on entropy?

On the book "Applied Differential Geometry" by William Burke we see a discussion about thermodynamics in which the following is said: A thermodynamic system is a homogeneous assembly that includes ...
0
votes
2answers
45 views

is this explanation of 2nd law of thermodynamics correct?

Second law of thermodynamics states that we cannot take heat from a hot source and make it 100% useful work. Is this because the heat is high disordered energy (ie molecules moving in a disorder ...
1
vote
2answers
36 views

Work applied to a thermodynamic system

What are some examples of a thermodynamic system where no work is done on the system, but the first law is applied? Work in thermodynamics is based around volume. Would that mean if the system's ...
0
votes
0answers
29 views

What happens when a semipermeable membrane allows only one solute to pass through?

I'm essentially a medical student where we deal a lot with osmosis. But when we are taught, it is done generally with only a single solute in consideration. What if two different solutes are used on ...
0
votes
1answer
65 views

Thermal average, thermal fluctuations

I've a doubt concerning the physical meaning of "thermal average" and the "thermal fluctuation" in the canonical ensemble. Let's consider a very simple thermodynamic system: N particles, at fixed ...
1
vote
2answers
118 views

Is work done on a system always the negative of the work done by the system? [duplicate]

Consider the following situation. A block slides on a rough surface. We have already given it an initial velocity. I consider my system to include only the block. Due to friction, the table performs ...
0
votes
5answers
49 views

How Heat is constant in adiabatic process

Consider adiabatic cylinder with a piston attached. $Q=0$ in this case and Work done is equal to change in internal energy. If I do work on the piston then its internal energy increases and so its ...
1
vote
0answers
10 views

What would be a suitable textbook of first semester physical chemistry? [duplicate]

I am going to take PChem I in my biochem dept next sem, which is a watered down version of the PChem course in Chem dept. It basically covers thermodynamics and a little bit of quantum stuff. The ...
0
votes
0answers
23 views

easier ways to cool things using electricity compared to phase changer

I can't seem to find any other ways to cool things using electricity. I understand how a phase changer works, but the whole things takes up alot of energy to cool down quite a few degrees and is ...
1
vote
1answer
30 views

What is the relation of particle velocity, temperature, and reaction activation energy

So, this curiosity has arisen for a fun project I thought I'd tackle, where I'm attempting create a crude simulation of an internal combustion cylinder. I wanted to explore the particle level ...
0
votes
0answers
40 views

applications of second law of thermodynamics

Second law of thermodynamics applies ONLY to thermal engines? Only in cases where we have heat involved? It won't apply to a mechanical machine that works without friction, right? Also will it apply ...
0
votes
0answers
19 views

Can the flow of hydrogen in a fuel cell be modelled as adiabatic?

Okay, so right off the bat I'll admit I need this for a problem I'm working on. Not homework though, a project, as a matter of fact. I'm considering taking compressibility effects into account, but ...
3
votes
1answer
54 views

Constant Temperature Cooling

In my thermodynamics textbook there is part of a question that seems to be a contradiction. ...Superheated refrigerant R-134a at 20 C, 0.5 MPa is cooled in a piston/cylinder arrangement at constant ...
-1
votes
2answers
80 views

Is Moon too hot?

I find it puzzling that Moon's maximum "daily" equatorial temperature is almost 400K. Earth's theoretical black body temperature would be 279K at 1AU, and Moon is the same distance from Sun, yet its ...
0
votes
1answer
54 views

Chemical Potential in the canonical and grand canonical ensemble

I'm studying the ideal Fermi gas from "Statistical Mechanics", by R. K. Pathria. In particular, the following formula, which can be found on page 237: \begin{equation} \mu=\left(\frac{3N}{4 \pi g ...
1
vote
0answers
36 views

Definition of emissivity?

A have come across a definition of emissivity which is along the following lines: Emissivity is the power emitted per solid angle per frequency per surface area. This definition, however seems ...
2
votes
1answer
52 views

Which will dry faster? [closed]

Assume that you have a wet shirt that you have just washed. You squeeze of the surplus water that can be squeezed out. Method 1: 1)You iron the shirt for 5 minutes and then hang it out to dry out in ...
3
votes
1answer
50 views

What phenomena occur in a low voltage arc between copper and graphite electrodes, and why is the result dependent on electrode polarity?

I was playing around with a laboratory power supply, drawing arcs between electrodes of various materials. I noticed phenomena that I found interesting, and couldn't really explain myself: The ...
0
votes
0answers
29 views

Computing Maximum Heat Capacity

I've encountered a problem in my statistical mechanics class that I'm not sure I'm approaching correctly: Consider a system of N interacting spins. At low temperatures, the interactions ensure that ...
1
vote
0answers
31 views

How to integrate to find the view factor of two parallel disks of different radii? [closed]

You have two parallel coaxial disks of different radii. I have tables that give me the value as $$F_{ij} = \tfrac{1}{2} [S - \sqrt{S^2 - 4(r_j/r_i)^2}]$$ where $$S = 1 + \frac{1 + R_j^2}{R_i^2}$$ ...
1
vote
1answer
57 views

Why does work done ultimately culminate as wasted heat?

Come to think of it, the work done on a body is converted into some form of energy.But why is it that it ultimately tends to produce heat? In physics we all talk about energy dissipation in the form ...
0
votes
1answer
43 views

Why we have a leak in the pipe if the fluid pressure is lower than the atmosphere

I've read in many books that if our flow pressure is lower than the atmospheric pressure then we'll have a leak in our pipe, but I already know that the flow is always from the high pressure point to ...
-2
votes
1answer
55 views

what does second thermodynamic law really states?

I read that the second thermodynamic law says that entropy in an isolated system always increases with time. That is okay, but how does this apply to energy transforming devices and other systems that ...
0
votes
1answer
44 views

In situations where we have entropy decrease, are we violating second law?

When we heat a material and this heat solidifies it (eg. when we cook an egg), isn't that decrease in entropy? when we have an endothermic reaction that produces larger molecules (synthesis), don't we ...
1
vote
0answers
45 views

if copper is heated, does it become negatively charged?

i'm reading "Electronics for inventors" and there's this part where it says that free electrons never escape material due to electrostatic attraction with positive ions, but if heated, electrons are ...
0
votes
1answer
45 views

What are the major flaws of the “caloric” theory of heat? [closed]

I was reading about the history of thermodynamics and came across Lavoisier's idea of heat. He proposed that heat was a fluid. I am curious to know what are the major drawbacks of this theory. I know ...
0
votes
1answer
37 views

Isothermal/isochoric/adiabatic process

I have a metal tin full of xenon, with a volume of 600cm3 at 20 celcius. I need to work out what will happen if I cool the tin to -40 celcius. I need to work out the new volume of the tin at this ...
0
votes
0answers
15 views

what are the direct real life applications of analysis of ferromagnetic materials?

I carried out Statistical analysis of ferromagnetic materials using Monte Carlo simulation, what are the contribution to knowledge based on the research work
1
vote
0answers
28 views

What are the implications of phase transition on electromagnetic device? [closed]

for the analysis of ferromagnetic materials on which I confirmed existence of Phase transition using Monte Carlo simulation implemented on Mat lab. contribution to knowledge are required.
0
votes
1answer
48 views

Thermodynamics cooling curve question

I'm given that a solid is heated, beyond melting point and then the temperature of the liquid is 90 Celsius. When it cools, the temp falls to around 80 Celsius and stays constant for a period of ...
1
vote
1answer
40 views

Calculating heat loss [closed]

I am given that the specific heat capacity of tin is $0.394k~\mathrm{J\,kg^{-1} K^1}$ I am to work out how much heat is lost by a block of tin with mass $100~\mathrm{kg}$ when it cools from $100$ to ...
1
vote
1answer
40 views

Relation between Pressure and volume in adiabatic process?

Why in adiabatic compression and expansion small volumetric change occurs while in isothermic compression or expansion very small pressure is applied and volume changes very significantly i am ...
1
vote
0answers
35 views

What is an extremal horizon?

In the contest of holography and thermodynamics, what is an extremal horizon? I am going through a paper by Hartnoll, Santos - Disordered Horizons: Holography of randomly disordered fixed points. They ...
0
votes
1answer
34 views

Entropy of environment of pendulum?

I remember reading a statement along the lines of: Suppose our system is a simple pendulum. Then the entropy change in it is overall zero because the system is periodic. However, the entropy ...
1
vote
1answer
44 views

Adiabatic compression and expansion and isothermal expansion? [closed]

Please help me in understanding the concepts Why in adiabatic compression and expansion small volumetric change occurs while in isothermic compression or expansion very small pressure is applied ...
2
votes
3answers
127 views

Where does the energy go when engine braking?

If you're in gear in a car and not accelerating, the car slows down faster than it would from just air resistance and tire deformation. In normal braking, the energy is turned into heat from the brake ...
1
vote
3answers
63 views

What's happening to my metal pot that makes boiling water so noisy?

When starting a fire in a metal wood stove, you can often hear the metal "ping" slowly at first and then faster as the stove heats up. Once the stove has been running for awhile and has heated up, the ...
0
votes
1answer
29 views

A counterexample to the Law of Stable Equilibrium?

This is the "Law of Stable Equilibrium", according to Hatsopoulos and Keenan: A system having specified allowed states and an upper bound in volume can reach from any given state one and only ...
0
votes
0answers
17 views

Relation between Light Intensity and temperature of air

First, I switched on my bulb but not the air-conditioner. Next I switched on my air-conditioner and yet kept the bulb on. I noticed that when the air-conditioner was switched on , the same bulb's ...
0
votes
0answers
17 views

How much power is being actually delivered by an electric heater to a cooking pan?

I've been doing experiments on an electric heater heating a cooking pan filled with 2 litres of water, from 20°C to 70°C; now I'm trying to draw a theoretical heat transfer model thath should match ...
1
vote
2answers
142 views

Is this conceptualization of blackbody radiation logical/correct?

From what I understand, a blackbody is a body which does not emit radiation as a result of atomic excitation/relaxation but rather solely due to the kinetic energy of its particles due to interactions ...
0
votes
2answers
63 views

Why is the interaction energy of a dipole and a magnetic field *negative* when they are parallel?

The interaction energy between a magnetic moment, $\mu$, and an applied magnetic field, $B$, is given by $$\varepsilon=-\mu \cdot B$$ That negative sign is confusing my inuition. If we expand the ...