5
votes
1answer
2k views

Magnetic field insulators

I was wondering if there is any way to stop the magnetic field, without having the insulator turned into magnet. Let me present this as a simple case, there is a magnet to the left and a piece of iron ...
2
votes
0answers
359 views

Magnetic Field at center of solenoid - Is this correct?

I've seen some different ways to compute tha magnetic field at the center of a solenoid, and sometimes people say that the result $B=\mu_0 n i$ is just an approximation. Well, I've thought on this way ...
2
votes
0answers
634 views

Relationship between current, voltage, magnetic field in a torus

I'm trying to find the relation between current density $\boldsymbol{j}$, voltage $v$, and magnetic field $\boldsymbol{B}$ for the time-harmonic approximation in a cylindrically-symmetric coil (a ...
10
votes
1answer
490 views

How would you swim in inviscid water?

The viscosity of water creates drag on swimmer's body so its effect is to slow down the swimmer. However the viscosity seems to be essential for pushing the water backwards by the swimmer's arms and ...
1
vote
2answers
921 views

Water pressure on slanted wall

Water pressure is simply $pgh/2$ for a vertical wall parallel to the depth of the water at exactly the half the water's depth. Suppose the wall is tapered (angled) slightly at around 2 degrees from ...
2
votes
2answers
8k views

How to estimate the physical size of a molecule?

I'm reading some chemistry-related papers that employ concepts of droplet evaporation. Since I am no chemist, I am wondering: How can I estimate the actual size of a molecule, say succinic acid? An ...
0
votes
2answers
3k views

reflection at speed of light when both mirror and viewer is travelling at the speed of light [duplicate]

consider me sitting on the top of a train which is travelling close to the speed of light, will I be able to see my image on a mirror which I'm holding in my hand??
1
vote
2answers
810 views

Vaporizing ethanol from liquid

What is going on here http://youtu.be/LQFmKPA-iAg Is ethanol leaving the liquid? If so, why? Does the pressure add energy to the ethanol molecules causing them to gasify and move rapidly near border ...
4
votes
0answers
198 views

The Hamiltonian for clocks?

I am rather a theoretician and looking for a formalism to represent biological clocks by Hermitian operators. The simplest thought model I am looking for is a formal representation of a clock (for ...
1
vote
0answers
134 views

virtual air-surface temperature difference above a water body

I'm trying to work through the equations for the following paper: http://onlinelibrary.wiley.com/doi/10.1029/2009JD012839/abstract and am trying to understand the concept of virtual air temperature, ...
7
votes
2answers
258 views

How to cut a stone on on a White Dwarf

I've heard that white dwarfs are extremely dense and hard. So, if I had a piece of white dwarf matter, would it be possible to cut it (or otherwise) into a custom shape? How could one do that?
0
votes
0answers
180 views

Calculating rotor torque out of mass center

Suppose I have an engine with propeller. I know there is aerodynamic force pushing the propeller opposite direction the engine is turning it. One component of this force is creating lift, but second ...
1
vote
1answer
331 views

Navier-Stokes equations: conservation of momentum

The first Navier-Stokes equation (conservation of mass) says: $\vec \nabla \cdot \vec v=0$ For a stationary flow, the l.h.s of the second equation is (conservation of momentum): $\rho \frac{D\vec ...
1
vote
2answers
238 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
3
votes
1answer
339 views

What is the largest diameter an optical fiber can have? - for nonimaging visible light transmission

Is there any theoretical limitation on the size of the diameter of an Plastic optical fiber? I would like to transmit visible sunlight through it. I see bundles of small cores available but wouldn't ...
4
votes
2answers
247 views

Non-local Lagrangian contact interaction

Conside a contact interaction given by a delta function on their worldlines. Use a gauge fixed Lagrangian for two point particles in terms of their proper times $t$ and $t^{\prime}$. Is it possible to ...
-12
votes
1answer
325 views

Isn't searches for dark matter crazy effort? [closed]

There are a lot of crazy quests in astrophysics, one of them is searches for dark matter. How someone could observe dark matter while it is far away?
2
votes
4answers
579 views

How does light behave within a black hole's event horizon?

If the event horizon of a black hole is the distance from the center from within which light cannot escape, imagine a person with a flashlight falls into the black hole. He points his flashlight in a ...
1
vote
0answers
69 views

What do the components of light velocity look like in polar coordinates?

The Schwarzschild solution makes use of polar coordinates, and I'm wondering how the different components of velocity of light change with the position. Might I get some examples of light velocity ...
2
votes
2answers
277 views

Is everything pre-decided? [closed]

"There is nowhere in the universe where the laws of physics are violated." Considering this general to be true,can i conclude that everything is pre-decided? I can explain this in the following ...
0
votes
1answer
80 views

Whether Au-Ga-Bi ternary phase diagram be calculated theoretically

Currently, my experiment involves the three elements: Au, Ga, Bi, and I need Au-Ga-Bi ternary phase diagram to explore the ...
1
vote
1answer
389 views

Optical illusion of car wheels, speeding up [duplicate]

Perhaps it is some free moving spinner attached to the wheel, but as opposed to this question: Why does the wheel of a car appear to be moving in opposite direction? I have seen car wheels that appear ...
1
vote
1answer
47 views

Charge in terms of wavefunctions

For a charged quantum particle, say, an electron or a quark, how in the particle's wavefunction is the electric charge represented? Is it truly possible to represent electric charge using the wave ...
1
vote
2answers
155 views

Use something that slower than light in Michelson–Morley experiment

Follow by the Michelson–Morley experiment, What happen if we use something that has a speed lower than light instead of light in Michelson–Morley experiment? How about the result?
3
votes
1answer
1k views

Why do black lights show bacteria and proteins?

Why are blacklights used to show proteins and bacteria? Is it related to their ability to make white colors glow? Don't black lights just radiate in the ultraviolet/purple range?
4
votes
1answer
166 views

What is an anapolar moment?

I just read this: Anapolar Dark Matter I'm not sure i've heard the term 'anapolar' before, so i google and i found this: http://en.wikipedia.org/wiki/Toroidal_moment This confuses me, my ...
3
votes
2answers
249 views

How to calculate resistance of bunches of wires

I figure that the resistance of multiple wires would work just like adding in parallel, a bunch of wires that is. But couldn't any wire just be viewed as a bunch of wires, albeit small ones? I know ...
5
votes
2answers
204 views

How does current flow in a irregularly shaped heterogeneous resistor?

The motivation for my question is understanding how electricity gets through your skin as opposed to running along it, and how the presence of things like water on the skin affect the relative ...
2
votes
3answers
2k views

How does energy convert to matter? [duplicate]

To my understanding, matter and energy are one and the same. Shifting from $E$ to $M$ in Einstein's famous equation requires only a large negative acceleration. If $M$ really is $E/c^2$, does that ...
2
votes
3answers
11k views

Why do current-carrying wires heat up?

Obviously wires heat up too, but why do they heat up? And for the same reason, why do we get electrical burns?
6
votes
1answer
334 views

Photons: Collection of Wave Packets that produce a plane wave

Is it possible mathematically for photons, which behave as individual Gaussian wave packets, to combine in such a way that the approximate result is a plane wave at one particular frequency (i.e., the ...
-2
votes
1answer
113 views

Speed of Light Question and Einstein [closed]

Einstein's clock experiment. What would happen if you were to travel at the speed of light or faster than the speed of light towards the clock? Can we translate this into traveling large distances ...
-1
votes
1answer
461 views

Understanding centripetal force vs frictional force diagrams?

I have an actual physics problem and also a conceptual question to go with it. From some test prep I was presented with this straight-forward question: What is the minimum radius that a cyclist can ...
0
votes
0answers
700 views

Is it theoretically possible for a person to pass through a solid wall/object?

I understand that matter cannot pass through other solid matter because of the electrons that orbit an atom prevents this but I was curious to know if it is theoretically possible to somehow get ...
1
vote
2answers
495 views

Is it possible see an invisible light with something similar to a normal lens of an eyeglass? [closed]

Let's say that I am a spy in a room with a lot of people and I want to communicate with my friend using Morse code via a light signal. Does there exist a type of light (laser or otherwise) that is ...
12
votes
5answers
941 views

Why are wires in simple circuits approximated as equipotentials?

I just answered this question: Voltage in a circuit by asserting that any two points joined only by a wire, but no other circuit elements, are at the same value of the electric potential. It is, of ...
1
vote
2answers
125 views

How would a diffraction pattern change if the atoms were triangular instead of spheres?

On a related note, what's a good book/source that would answer questions that go very in depth with these kinds of "what if" questions because I am also asked the same if the atoms were long cylinders ...
1
vote
1answer
687 views

Thermal Penetration Depth discrepancy

I've been working on a project that involves thermoacoustics, and one of the commonly-used values in this field is know as the thermal penetration depth. It is calculated as follows: $$\delta_k = ...
1
vote
2answers
452 views

What is wrong with this form of the Maxwell-Faraday equation?

What is wrong with this form of the Maxwell-Faraday equation? $$\oint \vec{E}\ \partial \vec l= \bigcirc \hspace{-1.4em} \int \hspace{-.6em} \int \frac{\partial \vec B}{\partial t}$$ "Line integral ...
9
votes
2answers
853 views

Spin - where does it come from?

I study physics and am attending a course on quantum field theory. It is hard for me to draw connections from there to the old conventional theories. In quantum field theory spin originates from the ...
0
votes
1answer
247 views

Formation on image on screen?

When we first learn elementary geometrical optics, the first thing taught to us is the two broad divisions of the type of reflection.-Regular and Irregular or Diffused. The difference in cause for ...
4
votes
2answers
226 views

Voltage in a circuit

Suppose I have a following circuit: I do not understand, why the potential difference between the points $c$ and $d$ is equal to the potential difference between the points $b$ and $a$? That is, ...
2
votes
3answers
895 views

Question regarding inverse relation of resistance with area of cross section

It is said that resistance is inversely proportional to area of cross section. But greater area will have greater electric flux, and greater electric flux will have greater magnetic flux, and greater ...
7
votes
1answer
216 views

Is broken supersymmetry compatible with a small cosmological constant?

I understand that we can find the energy of a bosonic field in its vacuum state via $E_{vac}^{(B)} = \sum_{\vec{k},s} \frac{1}{2}\hbar\omega_{\vec{k},s}^{(B)}$ and a fermionic one similarly, ...
3
votes
1answer
531 views

Most general Feynman diagram

What is the most general Feynman diagram? Srednicki, in his QFT book, says: The most general diagram consists of a product of several connected diagrams. Let $C_I$ stand for a particular connected ...
3
votes
1answer
110 views

How does irradiance behave over time?

I am trying to clarify data on weather from the Royal Netherlands Meteorological Institute (KNMI); I have incorporated the Solar Position Algorithm (SPA), such that I can calculate sunset and sunrise ...
2
votes
0answers
52 views

If the measurement of the proton size is correct and it is lower that it was expected than what are the theoretical implications?

In the press release of the recent measurement of the proton structure, they barely mention various theoretical explanations for the effect. What is the most likely (not assuming now that the ...
28
votes
5answers
2k views

Is a proton collision (collisions like in the LHC) visible to the human eye?

I was curious if a proton collision is visible to the human eye. (This might sound like a really basic question and forgive me if it is. I am very inexperienced in Physics and just wanted an answer ...
3
votes
0answers
314 views

How is the Geometric Phase measured in the experiment?

I had read some papers that have mentioned the geometric phase (Berry phase) can be used to detect the quantum phase transitions in a quantum many-body system. My question is: How is it measured in ...
0
votes
0answers
97 views

Electrical properties of molten gallium arsenide

I'm looking for the resistivity and magnetic permeability of molten gallium arsenide, but can only seem to find the values for the solid material at room temperature (e.g., Wikpedia). Not even ...

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