Questions tagged [thermodynamics]

Covers the study of (primarily homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using the tag: [statistical-mechanics].

When to Use This Tag

should be used if your question discusses the time-evolution of a mostly homogeneous, macroscopic system – for example, a cold bottle of water in a warm bathtub. You can combine this tag with for a microscopic derivation of thermodynamical laws and maybe with the other ‘macroscopic’ tags, such as or , depending on your problem. Tagging a question as both and usually makes no sense unless in the context of .

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Why am I not burned by a strong wind?

So I was thinking... If heat I feel is just lots of particles going wild and transferring their energy to other bodies, why am I not burned by the wind? When I thought about it more I figured out that wind usually carries some humidity, and since…
Jinx
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Why are the laws of thermodynamics "supreme among the laws of Nature"?

Eddington wrote The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the…
doetoe
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How close can you get to lava before burning?

As the title asks: How close can you get to lava before burning? I know that it depends on an number of factors; speed of lava flow, wind direction/strength, type(?) of lava flow (related to speed, in part, I think?). I'm guessing it also depends on…
Alexander
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How does a heatsink on top of a CPU, which is hot, cool down your CPU?

A heatsink can be stuck on your CPU to cool it down. That heatsink feels cold when the system is not turned on. However when the CPU is turned on the heatsink is extremely hot. Isn't that contradictory to a certain extent? I expect a heatsink to…
38
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Does too little ice make my martinis watery?

When I make martinis, the recipe I use is 2.5 fluid ounces1 of gin2 and 1/2 fluid ounce dry vermouth3, shaken or stirred4 with 7 ice cubes5, then strained into a cocktail glass (I mix until it's cold enough, and not for some specific length of…
bmb
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Are internal combustion engines more efficient on cold days?

According to Carnot efficiency formula $\eta=1-T_C/T_H$, can we say that the engines of cars are more efficient on cold days where $T_C$ (the temperature of the surroundings) is less than on hot days?
richard
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Thermodynamic equilibrium - will the piston move?

Friend asked me this question and I didn't manage to solve it with basic thermodynamic reasoning. I believe this problem is easly solvable via numeric methods by choosing specific systems, though I prefer an analytic, more general and more intuitive…
Alexander
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According to the inverse square law, is the intensity at the source always infinity?

I'm trying to design a script for a Unity game that can accurately (give or take) simulate heat based on distance from a source. Using the inverse square law seems to be a way I can do this, but setting distance to zero always seems to set intensity…
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Why does the tongue stick to a metal pole in the winter?

since the Christmas season is here, I would like to ask a question about the movie, "A Christmas Story." In one of the subplots of the movie, Ralphie's friends were betting each other that their tongue would stick to to a frozen pole. Finally, the…
TanMath
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If your hair was on fire and you entered a vacuum, could you outlast the fire?

Let's say a person's hair was on fire and suddenly we (instantaneously) pumped all the air out of the (sealed) room, then after time period X we put all the air back. Is there an X such that we will put out the fire (and it won't start again), but…
Shalom
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Why is it more energy efficient to keep a certain temperature in my house (instead of stop heating)?

Today I got this recommendation German for: Savings-tipp of the month: Turn down your heating on leaving the apartment. But never turn it off completely. Room temperature reduction is much more economic than the reheating of a cold room* It…
pico_prob
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A heat engine based on rubber bands

In Feynman's treatment of thermodynamics, The Laws of Thermodynamics, $44–14$ Heat engines; the first law, Feynman said we can use rubber bands to make a heat engine like the one below. It consists of a bicycle wheel in which all the spokes are…
Hilbert
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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 number of vertices, $F$ is number of faces, $E$ is…
aeiklmkv
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What's the difference between different speeds of sound?

In astrophysics, I often come across the speed of sound. I understand that, broadly, it represents the speed at which perturbations travel through a medium. But there's more than one speed of sound. The most common seem to be isothermal and…
Warrick
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Chemical potential of particles with zero mass

Why massless particles have zero chemical potential?
Andy Bale
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