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

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Does stirring water in a bucket in whirlpool keeps it warm?

I did an experiment when I was a teenager. I want to prove/see what really went on in that experiment. When taking a bath, take a warm water in bucket and start taking a bath. You will notice that ...
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3answers
344 views

Has anyone theorized a connection between entropy and quantum uncertainty?

I apologize if this kind of idle theorizing is frowned upon here, but I was wondering if it is possible that the Second Law of Thermodynamics is a consequence of quantum uncertainty. I've heard ...
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2answers
3k views

Testing the temperature of an open flame

How, and what device do you need, to obtain the exact temperature of an open flame? For the purpose of this question, you wanted to maintain 375 degrees. You can control the flame, but have no idea ...
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1answer
191 views

What is the molecular model of heat of mixing?

Heat can be evolved or absorbed when two dissimilar liquids are mixed together at constant temperature and pressure. This is called the heat of mixing of the mixture. I'm trying to understand the ...
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0answers
63 views

How many times brighter could the stars shine without raising the temperature of space?

If my understanding is correct, the temperature of space (as defined by the temperature that a black-body will reach) has been decreasing since the big bang. It has never increased. Additionally, ...
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2answers
596 views

Does the global financial system violate laws of thermodynamics and energy conservation? [closed]

For the past years I am thinking about relating concepts from physics to concepts from economics. Especially since the financial crisis made obvious the instability of the financial system I ask ...
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137 views

2 streams going into an engine and 2 come out. Find the enthalpy?

Problem: Steam supply to an engine is made of two streams that mix before entering the engine. Stream 1 flows at a $.01\frac{kg}{s}$ with an enthalpy of $2952\frac{kJ}{kg}$ and a velocity of ...
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1answer
2k views

Meaning of what C. P. Snow said about the laws of thermodynamics [closed]

My native language is not English and I am having hard time understanding the meaning of the following statements which are to explain the laws of thermodynamics. The 1st law: you cannot win ...
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3answers
5k views

What type of substances allows the use of the Ideal Gas Law?

I know that I can use the ideal gas law with pure gases or pure liquids. But can I also use the ideal gas law at saturated gases and saturated liquids as long as they aren't two phase substances?
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1answer
1k views

What happens to temperature when pressure is constant in a cylindrical piston of saturated liquid ammonia?

Let's say I have a cylindrical piston containing saturated liquid ammonia that is fitted with an electrical heater and a paddle wheel for stirring at an initial pressure and an initial temperature. ...
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566 views

How do I determine the Internal Energy of ammonia at a pressure in temperature when the steam table doesn't say it

I just bought a steam table for my thermodynamics class since they don't allow use to use the one from the book for the tests. This one is different from the one in my textbook as it doesn't give the ...
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581 views

Do the properties of two streams flowing into an engine add together when they mix?

Let's say I have two stream supplys that have separate mass flow rates, enthalpies, and velocities that flow into an engine. Upstream of the engine's inlet, the two streams mix to form one stream that ...
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1answer
183 views

Does a water cooker element have to be 100C to get water to cook?

I understand that a water heater element is basically just adding energy to the mass of water in the container. So does that mean that the heater element only has to keep adding energy while the water ...
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2answers
814 views

Does power from a resistor perform work or heat transfer?

Let's say I have a cylindrical piston filled with air and fitted with an electrical resistor. The resistor has a current going across it and a voltage for a certain amount of time. My system would be ...
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1answer
368 views

Thermodynamic System: Windmill

There is a closed system that is just a windmill attached to a rotating shaft that can mechanically power something. I know the system produces work on the surroundings from the rotating shaft and ...
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0answers
236 views

Does a thermally expanding torus experience internal stress?

I'm trying to learn continuum mechanics and thermo-mechanics. As we know, heating an object increases the mean atomic distance $a_0$ of the atoms in a rigid body. Let's assume it is a linear elastic ...
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1answer
786 views

Calculating the heat capacity of a system

I have started reading Statistical Physics by F. Mandl and I would appreciate some help with the following exercise A system consists of $N$ weakly interacting subsystems. Each subsystem possesses ...
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1answer
744 views

Why does blowing on someone who is wet feel colder than on someone who is dry?

The title says it all. If I'm standing in the wind and I'm wet, I feel much colder than when I'm dry. This is true no matter how warm or cold the water. Why is this?
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1answer
113 views

Finding two dimensional critical point

I'm reading an article about bi layered membranes which state that for the free energy function $f(\theta) = \theta \ln \theta + (1-\theta)\ln(1-\theta) + \chi \theta (1-\theta)$ Where $\phi_i$ is ...
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1answer
295 views

Melting point, is it determined only experimentally?

I am interested in the underlying physics of the concept of a melting point, a temperature at which an object tends to gain enough energy to break the bonds that hold it together and be in a liquid ...
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2answers
344 views

why egg cooks slowly in mountains?

A quick Google tells me "Because water boils at a lower temperature at high altitudes". But I am not being able to understand this answer and fill-in the gap. Like, how does an egg cook in the first ...
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5answers
3k views

How do we perceive hotness or coldness of an object?

Some objects, especially metallic ones, feel cold on touching and others like wood, etc. feel warm on touching. Both are exposed to same environment and are in their stable state, so some kind of ...
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1answer
1k views

How does liquid convert to gas on getting thermal heat energy?

Say for example, when we heat, water converts to steam gas. How does it happen? What happens underneath giving rise to breaking of bond between molecules in liquid state and spreading them in gas ...
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1answer
189 views

Does thermodynamic processess affect phase transition in solid state metals

I read an article about phase transitions and I read about thermodynamic processes such as Adiabatic process, Isochoric process, Isobaric process, Isothermal process Do these processes affect phase ...
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4answers
9k views

Are specific heat and thermal conductivity related?

Are there any logical relationship between specific heat capacity and thermal conductivity ? I was wondering about this when I was reading an article on whether to choose cast iron or aluminium ...
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2answers
166 views

Optical element is heated by laser: is it possible to get oscillating heat distribution?

Imagine that we have thin optical element, which is irradiated by laser. Laser heats element, so there is some heat distribution in element. There is a heat sink through upper and lower element faces ...
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3answers
485 views

Will the water added to an ice piece freeze?

Water, at room temperature is poured into a hole made of a block of melting ice(kept at room temperature).I was wondering if the water will ever freeze? Thank you.
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1answer
199 views

Depalma Free Energy fields

Few years ago I read some papers about Free Energy, written by Bruce de Palma, a physicist who is said to be the inventor of the N-Machine, which is an device that works with free energy latent in the ...
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5answers
310 views

Is the cooling rate of a (very) cold object, sitting next to an AC higher or lower?

In more detail: If i have two soda cans, both are cooled to exactly 4 degrees celsius, And i put one in a 25 degrees room, and the other next to an AC vent set to 16 degrees. After three minutes, ...
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1answer
202 views

Can i use coils with compressed air to make a superconductor?

What im saying is inside pipes i am going to use compressing so that that in the places with low pressure they cool the superconducotor. is this possible? Can i use this concept to make ...
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3answers
417 views

Problem with an electricity / thermodynamics assignment

I've been trying to figure this one out for a while on my own, so I'd like to ask for your help if you could offer some. The task states: A heater made out of a wire with a diameter $R = ...
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3answers
369 views

Is the continuous transformation of energy from one form to another one free? Or it consumes some quantity of who knows what?

Sorry for the unclarity. I probably created some bias in your mind having tagged my question with energy-conservation and conservation-laws. I simply consider that, relatively independently of ...
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0answers
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What are typical values of the critical thickness of insulation?

As most people who've had any elementary heat transfer course are aware, when insulating a pipe, wire, etc, there is a critical thickness for the insulation below which it causes greater heat transfer ...
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2answers
339 views

simulations at constant pressure-volume and constant volume-temperature

I have read some papers where the authors perform simulations at constant pressure and constant volumen or sometimes constant volume constant temperature. My question is when is it better to use one ...
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1answer
109 views

What are the patterns appear after kernel averaging?

Having a 2D map filled uniformly by random values (Figure:top-left) to demonstrate a disordered phenomena, the next maps are ...
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2answers
11k views

How does a change in temperature affect relative humidity

Assume that the air pressure and the amount of water in the air stay constant. How can I figure out how much a change in temperature affects the relative humidity?
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5answers
2k views

Entropy of radiation emitted into space

In several papers I see something equivalent to the following expression for the entropy of radiation given by an astronomical object such as the Sun (assuming the object can be approximated as a ...
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1answer
275 views

Trying to understand a step in deriving Maxwell-Boltzman statistics

In the Wikipedia article on Maxwell–Boltzmann statistics, there is a point in the derivation that stumps me. When I get to where $\displaystyle W=N!\prod\frac{g^{N_i}}{N_i!}$ is quoted as a count ...
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0answers
427 views

Heat equation and Bessel's function [closed]

Could someone please explain why if the time-independent heat equation can, via changing of variables, take the form of Bessel's equation that the $\sqrt\lambda$ should take the values of the zeros of ...
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1answer
6k views

Best way to solve P-V-T Question

Typically in an exam or problem set we have a problem that's like this: Determine the specified property at the indicated state of water. Locate the state on a sketch of the T-v and P-v diagram. p= 3 ...
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1answer
733 views

Ceramic vase filled with boiling water makes a sound. Why?

I had some old flowers in a vase and noticed the water had become really stagnant, causing the whole room to smell like a fart. So I tipped out the flowers and the old water, and poured some boiling ...
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2answers
359 views

Why does a firebrand glow brightest before it burns out?

I've noticed this in match-sticks, and mango wood. After the flames die out, the brand glows red for a while. The glow is brightest right before it dies out. My guess is that immediately before the ...
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3answers
1k views

How would you store heat?

Um .. naive question perhaps but if somebody wanted to store heat, how would they go about it? Can heat be stored? I'm told that decomposing kitchen waste in a closed vessel results in a rise in ...
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1answer
10k views

Why is my tupperware sealed after heating it up in the microwave?

I had a vegetable soup in a crystal tupperware and I put it in the microwave to heat it up. The funny thing is that when I took it out, it was impossible to open it up. The lid is bent towards the ...
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4answers
37k views

Heat transfer calculated from the specific heat formula

Say I have 10g of silver, whose specific heat is known to be 0.235. I've heated it up from 50.0C to 60.0C. How much heat has been transferred? The equation is: $$ Q = C_pm\Delta t $$ where Cp is ...
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2answers
1k views

Which phenomena is involved in the clothes drying process?

There's this question that has been bugging me most of my life: how is it that wet clothes left hanging to dry, get actually dry? If I get it right, the clothes are a mesh of fibers (we could assume ...
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1answer
3k views

Reversible adiabatic expansion

I am confused with adiabatic expansions. I have a homework problem wherein 2.75 moles of an ideal gas at 375 K expands adiabatically with an initial pressure of 4.75 bar and a final pressure of 1.00 ...
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3answers
257 views

Does entropy measure extractable work?

Entropy has two definitions, which come from two different branches of science: thermodynamics and information theory. Yet, they both are thought to agree. Is it true? Entropy, as seen from ...
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1answer
372 views

$(\mu,P,T)$ pseudo-ensemble: why is it not a proper thermodynamic ensemble?

While teaching statistical mechanics, and describing the common thermodynamic ensembles (microcanonical, canonical, grand canonical), I usually give a line on why there can be no $(\mu, P, T)$ ...
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Function of air conditioner

What i always thought that air conditioners blow the cool air without knowing that they actually take the warm air from indoor and from outdoor. But whats the point of taking air from indoor and ...