# All Questions

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### Charge on capacitor plates in series combination?

Suppose 2 capacitors are connected in series, the plates connected to the battery terminals receive charges $+q$ and $-q$, and the isolated plates in the combination receive equal and opposite charges ...
799 views

### Why does the milk frother on my coffee machine make so much noise?

I have a Sunbeam home espresso machine with a steam wand. The steam roars out straight from the end of the wand. When it's first placed in the cold milk it really screams! Once the milk has a bit of a ...
416 views

### Does a Peltier Thermoelectric layer make a good regulator for LN2 heat-sink interfacing

I understand that when cooling water with LN2 directly (through pipes for example), that it can be too effective, freezing the water (and blocking the pipe). From what I read, regulation of the heat ...
528 views

### Why is information in a volume proportional to it's surface area?

I read the wiki article on the holographic principle, but it never answered this question. Can anyone explain the math that leads to this conclusion?
9k views

### Is it possible for the planets to align?

We've all heard the statement that on the 21st of December, the planets in the solar system will "align" from the point of view of the Earth. I assume this means that they would all be in the same ...
1k views

### How to relate speed of sound with relative humidity?

I am exploring the idea of measuring the humidity of a space using sound waves, however I am having trouble finding a mathematical relationship between the speed of sound and the humidity level. ...
346 views

### few fermions in a harmonic trap — position density matrix from diagrammatics

I'm trying to calculate the momentum distribution of a 1D system of non-interacting identical fermions in a harmonic trap. Given Feynman's answer (from his Statistical Mechanics book) for the ...
1k views

### When is the right ascension of the mean sun 0?

I understand that the right ascension of the mean sun changes (at least over a specified period) by a constant rate, but where is it zero? I had naively assumed that it would be zero at the most ...
92 views

### Question on “new CNGS/OPERA measurement of neutrino velocity” (hep-ex/1212.1276)

A "new measurement of the limit on muon neutrino velocity with respect to the speed of light " by the OPERA neutrino experiment in collaboration with CERN has become public recently, as preprint ...
118 views

### Is there Pair production in between charged plates

In classical electromagnetic theory, If parallel plates are charged oppositely and placed close to each other, there will be no charge will not flow from one plate to another. How does this situation ...
248 views

### Electron hopping among molecules - Marcus equation

I'm running out of professors to talk to, and I need to clarify a couple of things for the sake of making a realistic model of electron travel through a mesh. This is about calculations of electron ...
579 views

### Angular Momentum of Diatomic Molecules

I have run into a problem trying to calculate angular momenta and I wonder if someone can set me straight. I think I know that the lowest order rotational mode should have angular momentum of h, and ...
165 views

### Confined in a box, what is the average distance between a particle hitting a side?

This particle, alone in the box, at a constant velocity $v$, travels in straight lines until hitting a side of the hollow cube, bouncing off in a random direction independent of incident angle (I know ...
164 views

### Data requirement to determine proportionality

A common result of theoretical analysis in physics is some sort of relation derived from physical parameters and typically expressed in the form of a non-dimensional parameter. These scale relations ...
78 views

### Why don't black holes have magnetic hair? [duplicate]

Possible Duplicate: What happens to an embedded magnetic field when a black hole is formed from rotating charged dust? It is well stablished that the only hair a black hole can have is: ...
188 views

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### paper about black branes and implications to 4d black holes

This paper makes a case for piezoelectric response (electric dipole moment under mechanical oscillations) of black branes. This paper does not make an implication of their results for 4D black holes ...
847 views

### Why can't light escape from inside event horizon of Black Holes?

The simple answer: Its because Gravity of Black Hole there doesn't allow it. See also this and this Phys.SE posts. Isn't it a classical answer? When we're unable to connect Gravity with Quantum ...
232 views

### Cyclic rotation of a Matrix

What is meant by a cyclic rotation of a matrix, specifically in proving that j*k-k*j=i*l where j,k,l are cyclic rotations of the Pauli spin matrices sigma x, sigma y, and sigma z
237 views

The Kolmogorov theory of turbulence indicates an energy cascade in turbulence. Is there a corresponding version of relativistic fluid?
2k views

### Usage of helium in MRIs

More and more articles pop up on the shortage of helium, and on the importance of it. Its usage in MRI's spring to mind for example. I looked it up and found out that helium is used for its 'low ...
462 views

### Blue-shifting as opposed to violet-shifting

A recent XKCD comic implies that the sky is blue as opposed to violet due to human physiology, and that animals more sensitive to shorter wavelengths will perceive the Earth's sky as the shortest ...