# Tag Info

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Landauer's principle (original paper pdf | doi) expresses a non-zero lower bound on the amount of heat that must be generated by computers. However, this entropy-necessitated heat is dwarfed by the heat generated through ordinary electrical resistance of the circuitry (the same reason light bulbs give off heat).

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Computers manipulate internal stored values "0" and "1" represented as different voltages. Every change 0-to-1 and 1-to-0 involves an electric current I passing through a circuit resistance R, which gives rise to ohmic or "Joule" heating.

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You would be wise to somehow determine the exact fluid used by the original manufacturer. Consider that each of the floats has a fixed density, and has a temperature marked on its hanging tag. So you need a liquid which will have the correct, different density at each temperature marked on a tag. In short, the liquid you choose must match both the ...

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There are a lot of misconceptions here so let's take it one step at a time. The entropy in classical mechanics is called the Gibbs entropy, $$S = - k_B \sum_i p_i \ln p_i,$$ where $p_i$ is the probability of some microstate $i$. This is essentially the same thing as Shannon entropy for physical systems. With this concept one can view knowing ...

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Rising bubbles of air in a liquid oftentimes are anything but spherical. These bubbles have haphazard shapes because they are rising and because they are interacting with other nearby bubbles. The combination of drag, turbulence, and mutual interactions prevents those bubbles from taking on a nice, simple spherical shape. Here's a rather non-spherical ...

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As the comments to the question have stated, in real gasses ( contrasted to ideal gasses which just bounce around elastically) there exist both elastic and inelastic scatterings controlled by quantum mechanical interactions. Photons are generated leading to what we call Black Body radiation and an isolated gas volume will lose energy according to the ...

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It is not thermodynamics that controls crystal formation at the atomic level, but quantum mechanics. Large crystals, from diamonds to clear ice crystals are a macroscopic manifestation of the underlying quantum dynamical level. The molecules that build up the crystal have such field properties, dipoles and quadrupole and even higher moments that have ...

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If the heat is transferred reversibly, the temperatures of the two bodies have to be the same. Transfer of heat from hotter to colder body is irreversible.

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You should be able to start with methylated spirits - ethanol with a bit of methanol mixed in to make it toxic and cheap (or ethanol if you can get your hands on it - but it will be expensive because of excise taxes unless you can prove "scientific exemption".) It is much lighter than water and highly miscible with it. Once calibrated you do need to seal it ...

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My guess is it's best to put each pizza into its own insulator, but then stack them for transport so that the stack has the same size and surface area a larger insulating container would have. Stacking the boxes in transport minimizes heat loss since it's proportional to exposed outside area. Opening a container would let significant heat out, so that ...

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What other variables I should know before it can be calculated? : I only know the values before the collision, for example the initial velocities VA,VB, initial temperatures, surface areas, etc. You need to know the $C_R$ coefficient of restitution, CR is the coefficient of restitution if it is 1 we have an elastic collision, if it is 0 we have a ...

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It's pretty much as you say. But it sounds as though you're trying to guess. I'd suggest a couple of little sketches and some first principles reasoning; see my drawing below Both the circles are my reversible heat engine. On the left, it is running "forwards" and yielding work $W$ from the nett flow $Q_C$ into the cold reservoir at temperature $T_C$ ...

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It's because normal ice, ice Ih, is less dense than liquid water. Ice Ih forms hexagonal crystals. The bonds in that crystalline structure make the water molecules slightly further apart than they are in the liquid form at the same pressure. That water expands on freezing makes water resist freezing as pressure increases. This in turn makes the fusion point ...

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For the sake of the explanation I will assume you mean a gas bubble in a liquid*. David Hammen names a few conditions for a bubble to be spherical, in fact you could summarize these all as: for a bubble to be spherical the surface tension has to dominate over other forces (per unit length). If surface tension is indeed dominant than the pressure in the ...

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When reaching the homogeneous nucliation temperature, thermal vibrations are sufficient to induce the phase change. Above, stronger perturbations are needed.

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There's a nitinol wire that stiffens when warm and softens when cool. It's been used in various patented heat engine applications. see this reference http://www.imagesco.com/articles/nitinol/09.html

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The statistical ensembles differ in the constraints imposed to them. In the canonical ensemble, the number of particles $N$, the volume $V$ and the temperature $T$ are fixed. In the grand-canonical ensemble, the number of particles is not fixed, it is determined by the chemical potential $\mu$, which plays the same role on $N$ as temperature on energy or ...

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There is a very nice property that works, in practice, for most systems that is that of equivalence between the Gibbs' ensembles in the thermodynamic limit. The prototypical example is that of the equivalence between the canonical ensemble and the microcanonical ensemble. One way to state it is to say that the free energy $F(T,N,V) \equiv -k_BT \ln Q(T,N,V) ... 1 tl;dr: Yes. Specific heat and temperature are different measurements. The specific heat of a material is a function of temperature that describes how much heat it takes to change the temperature of a material by a specific amount$\frac{dU}{dT}$. Statistical mechanics concerns itself with questions like this. If we integrate the specific heat function from ... 1 I think André Neves' answer to your other question says the opposite of what you think it says. But let me try to make it a little bit clearer for you, if I can. In André Neves' answer, he talks about a gas in a piston that's weighed down by 1000 pieces of lead shot, each weighing a small amount$m$. After each lead shot is removed, there is indeed a period ... 1 I will come up with an explanation that has to do with information. One possible interpretation of the second principle of thermodynamics is that, during an irreversible process, there is a loss of information about the state of the system that can never be recovered (this interpretation is mostly due to Jaynes). Now, when you perform (for instance) a ... 1 Do you mean efficiency or coefficient of performance (COP). The latter is the ratio of power needed vs amount of heat transported - and that is the more interesting value for heat pumps. The smaller the gradient against which you pump heat, the less energy you have to add. Think of it as "carrying particles of heat up a hill". If the hill is tall, you have ... 1 The heat generated in a computer has nothing to do with the reversibility condition in Landauer's principle. Computations can be carried out reversibly, if required. What can not be made reversible is the RESET of the computer. The first time we turn the machine on, the memory is in a random state, and it takes energy and entropy to turn that random state ... 1 Not only does your speed affect the amount of radiation that you receive, but this actually happens to the Earth and has been measured experimentally. You say: So basically in space, there is bound to be stray radiation, whether from the stars, or cosmic background, floating around right. and the most obvious example of this is the cosmic microwave ... 1 My previous comments are almost ok, your actual problem seems to be that you do not average over the magnetization. You are measuring <cos(theta)>, which is the average of m_x. So just change m = magnetization_cossin(); to magnetization_cossin(&mx, &my); where you define void magnetization_cossin(double* mx, double* my) { int x, y, z; ... 1 Your equation for$Q_{max}$gives the heat transferred for any ideal exchanger. The equation for$q_{max}$in the Wiki page gives the heat transferred for the ideal exchanger that maximizes the temperature change of one of the fluids. The maximum possible temperature change is$T_{h,i} - T_{c,i}$. The max temperature change occurs when either$m_h C_h \ll ...

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The thing you'll notice about a sphere is that it's symmetrical. very symmetrical. No matter how you rotate it, it looks the same. the surface tension pulls the surface of the bubble into a shape that has even surface tension over the entire bubble. The shape with even surface tension is a sphere. a sphere has the smallest possible surface area for an ...

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