question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>For small thicknesses of wire, it's pretty obvious why resistance affects thickness. (The electronics squeeze to get through). But after a certain thickness shouldn't the thickness become irrelevant?</p>
<p>For example if your trying to pour a bucket of water through a straw, the thickness of the straw is obviously... | g11479 | [
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<p>A picture in my text book shows a three dimensional wave packet dispersing, "resulting from the fact that the phase velocity of the individual waves making up the packet depends on the wavelength of the waves."
Does this mean a particle moving through space has a gradually diminishing probability of being in it's lo... | g11480 | [
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<p>I have a measurement method for which I want to study the measurement error by an error budget. Therefore, I listed all possible errors (error sources) (lets say $x_1, x_2, x_3,\ldots$). For each error $x_i$, I have derived an analytical expression from which I can calculate the resulting measurement error $\epsilon... | g11481 | [
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<p>Let $\mathcal N^{A_1\rightarrow B_1}_1,..,\mathcal N^{A_1\rightarrow B_1}_k$ be a set of valid quantum evolutions with equal input and output dimensions. And let the effect of a channel on a system $\rho_{A_1A_2}$ be: </p>
<p>$$\mathcal N^{A_1A_2\rightarrow B_0B_1}(\rho_{A_1A_2})=\int dB_0|b_0\rangle\langle b_0|\ot... | g11482 | [
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<p>Okay, my buddy tells me this:</p>
<p>Let there be a starship, ovoid, and me and my buddy stand each at the extremities of the ship, him below the roof, me on the floor.</p>
<p>We start a journey and the ship accelerates at a constant rate, let's say $1g$, in the direction of the axis of the ship.</p>
<p><em>My bu... | g11483 | [
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<p>Since neither the object nor its field could exist without the other, it would seem strange not to include the field energy as part of the object. But how exactly does the accounting go? How is the mass of the system divided between the rest mass and the field mass?</p>
<p>For a Schwarzschild black hole, the mass a... | g11484 | [
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<p>If you strip the valence electrons apart with a very short intense electromagnetic field the remaining core explodes in a so called coulomb explosion.</p>
<p>But experiments have shown that under certain cases fusion does occur in a manner, that the ions are accelerated and you get a non maxwellian velocity distrib... | g11485 | [
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<p>How much charge is on each plate of a 4.00-F capacitor
when it is connected to a 12.0-V battery?</p>
<p>I said 2.4 x 10^-5 C because there are two plates of a parallel plate capacitor. But the key said only 4.8 x 10^-5 C</p>
<p>Why?</p> | g11486 | [
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<p>This is a school exercise.</p>
<p>We tend to think that the action of a constant force produces a constant movement speed as well. How can you explain this situation in accordance with Newton's second law?</p>
<p>Because as the force will end up in a certain time that means there will not be a movement of constant... | g11487 | [
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<p>In the derivation of drift velocity I have seen two variations and want to know which one's correct.</p>
<ul>
<li><p>$s=ut+\frac{at^2}{2}$<br>
Assume that the drift velocity of any electron in any conductor is :
$$\vec{v_d}=\frac{\vec{l}}{t}$$
Due to the electric field the acceleration of electrons in any conductor... | g11488 | [
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<p>When I see a new accelerator in real life or on a picture, I always find it interesting to see how many thing I can recognize. In that way, I can also get a small first idea of how the accelerator is working.
Here is a picture, I have taken of LEIR at CERN<img src="http://i.stack.imgur.com/d8t7B.jpg" alt="LEIR"></p>... | g11489 | [
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<p>I'm suppose to write out reactions where atoms send out alpha radiation and decay. The book uses the 4-2 H, 4 as nucleon number and 2 as proton number, but isn't that wrong? The mass of helium is greater than the alpha particle due to two electrons? Shouldn't they use a different notation for the alpha-particle othe... | g11490 | [
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<p>The binding of quarks in mesons baffles me. It's an Occam's Razor thing.</p>
<p>Since a meson is a colorless, the simplest way to bind its two quarks together is to use a $U(1)$ Cartan subalgebra of $SU(3)$. That is, the two quarks would bind by exchanging only gluons whose color and anticolor components cancel out... | g11491 | [
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<p>I realize that the permittivity $\epsilon$ of a substance is easily calculated based on diffraction angles, but I am not satisfied with merely measuring it experimentally. I wish to understand its origin within the laws and equations of physics. I realize that it is a vector as demonstrated by the anisotropy of bir... | g11492 | [
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<p>My textbook and the following extract from feynman's lectures present the same idea regarding wavetrains and uncertainty in their wavelengths. Why is it that a wavetrain confined to some space has an uncertainty in its wavelength or the wave number? Is not a confined wave-train equivalent to a burst of successive pu... | g575 | [
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<p>When magmas begin to crystallise, a first step is the formation of a crystal nucleus around an impurity (nucleation centre), whereby a few of the right atoms get together to form a speck of a crystal. I know that impurities are not always necessary for crystallisation to occur but I'm curious to know what these impu... | g11493 | [
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<p>Electrostatic force between two charged particles depends on the magnitude of the charges and the distance between them. If the charges have mass $m$ and $m'$ then, what will be the total force including gravitational and electrostatics forces? Distance between them is $d$.</p> | g11494 | [
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<p>Can we treat any charge configuration as small point charges by using superimposition principle to derive electric fields, forces and other things ?</p>
<p>For example suppose we have a symmetrically charged cylinder, from the distance outside the cylinder, we can treat it like a line charge along the axis of the c... | g11495 | [
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<p>What is the "momentum" referred to in the energy momentum tensor from GR?</p>
<p>Is it $m\dot{x}$ or is it the canonical momentum $\frac{d}{dt} \left(\frac{\partial L}{\partial \dot{x}}\right)$</p>
<p>Also, I find it very difficult to think of the density and flow of momentum. Momentum is, to me, not an object th... | g11496 | [
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<p>It's said that potential energy is "energy of position." If an object is sitting on a shelf five feet above the floor, its potential energy can be thought of as equal to the amount of energy that would be involved in it falling off the shelf and onto the floor.</p>
<p>Conservation says that energy is neither creat... | g11497 | [
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<p>I have read in a few books that all Brillouin zones have the same volume, and I can vaguely see how it works, but have not been able to think up a formal proof.</p>
<p>Help?</p> | g11498 | [
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<p>The more I learn about General Relativity, the more it seems like it isn't fully understood. It seems that before it's full consequences were exhaustively understood, not 10 years after its discovery, QM came on the scene and stole the limelight. Now it seems like a "boring" field without much funding, even though a... | g11499 | [
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<p>I am trying to produce graphene with few layers(<10) on a TEM-Grid. Until now I've been trying this with the scotch-tape-method with slight modifications. Unfortunately it requires a lot of time und there are often TEM-Grids without any flakes of the required thinness.</p>
<p>Is there a more efficient way to pla... | g11500 | [
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<p>Currently i am studing about quantum confinement in semiconductors and came across effective mass approximation.but i am unable to understand this concept. what is the use of effective mass approximation in semiconductours.i am not a physicist so if possible please use less equations.</p>
<p>Advance thanks</p> | g11501 | [
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<p>My question is more about climate sciences, but I hope that it is still related to physics.</p>
<p>What would be possible atmospheric conditions for planet with some kind of "fire" ocean?
I had some thoughts about Venus and Titan (and about gas planet from BBC movie with iron rains and incredible winds), but nothin... | g11502 | [
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<p>Suppose an event is observed in 3 inertial frames K, K' and K''. The coordinates in K are $(x,t)$ in K' are $(x',t')$ in K'' are $(x'',t'')$. The K' and K'' coordinates are then Lorentz-transformed to K-coordinates: $(x',t') \rightarrow (x_1, t_1)$ and $(x'',t'') \rightarrow (x_2, t_2)$. Now there are 2 sets of coor... | g11503 | [
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<p>The data from the Planck probe's observations are in, and <a href="http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51559" rel="nofollow">according to the European Space Agency</a> they show a "hemispheric asymmetry in the cosmic microwave background (CMB)". Quote:</p>
<blockquote>
<p>an asymmetry in t... | g11504 | [
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<p>Does normalization of wave function mean that we are getting our state vector to unit length? If that's the case what does it mean physically? Also is the underlying vector space finite dimensional? If yes, then what is the dimension and how do I find the basis vectors? </p> | g11505 | [
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<p>In Classical Mechanics there's this notion of <a href="http://en.wikipedia.org/wiki/Configuration_space" rel="nofollow">configuration manifold</a>. Although I've heard about that a lot and although I often use that concept, I'm not sure I really understand them well because I've found no book talking about that, exc... | g11506 | [
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<p>Is this a correct formula for calculating the induced EMF of a wire after the current stabilizes/ or while it stabilizes in the beginning of a DC circuit? </p>
<p><img src="http://i.stack.imgur.com/8JKcE.png" alt="enter image description here"></p>
<p>What is the difference between the above and this:</p>
<p><im... | g11507 | [
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<p>I have task to compare eignevalues gained by exact calculation on electron in Coulomb attractive field (hydrogen) and gained by WKB method..
As far as I get, eigenvalues gained with exact method are E=13.6 / (n^2)
and for WKB method all i find is exact same answer E=13.6 / (n+l+1)^2 exept there is l.
I Don't underst... | g11508 | [
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<p>This question is similar to previously asked questions, but the responses to them are confusing and I think it may be better covered by listing out all the potential answers for clarity.</p>
<p>It's a simple and common question: why does light seem to travel more slowly in media which is transparent to its waveleng... | g11509 | [
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<p>Correct me if i'm wrong here, but if you consider the analogy of inflating balloon when explaining the universe expansion, then the center of the universe lies within the center of the inflating balloon and outside our space and time, so our own 3d universe is analog to the surface of the expanding balloon. Does tha... | g11510 | [
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<p>Yesterday I read that we can affect the path and the 'form' (particle or wave) of a photon after the fact (<a href="http://en.wikipedia.org/wiki/Wheeler%27s_delayed_choice_experiment" rel="nofollow">Wheeler's delayed choice experiment</a>). Part of what is puzzling me is the beam-splitter. Are the individual photon... | g11511 | [
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<p>Is there a scientific approach that can explain the <a href="http://en.wikipedia.org/wiki/Street_light_interference_phenomenon" rel="nofollow">street light interference phenomenon</a>? Everytime I walk past a Streetlight it turns off.</p> | g11512 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/24324/spacetime-expansion-and-universe-expansion">spacetime expansion and universe expansion?</a> </p>
</blockquote>
<p>So I've heard that space is expanding very quickly and that the redshift we see whe... | g56 | [
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<p>Fundamentally i want to know: <strong>How do holograms work?</strong></p>
<p>The problem with that question is that normally you will end up with pages and pages talking about:</p>
<ul>
<li>a laser</li>
<li>a beam splitter</li>
<li>a diffuser</li>
<li>the object being imaged</li>
<li>object beam</li>
<li>reference... | g11513 | [
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-... |
<p>Potential wells, such as infinite and finite potential well, have been the standard examples in quantum mechanics textbooks for tens of years. They started being only theoretical toy models but as time progresses scientists succeeded in fabricated them which resulted in the nanotechnology revolution.</p>
<p>1-Is th... | g11514 | [
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0... |
<p><img src="http://i.stack.imgur.com/wMjhh.jpg" alt="enter image description here"></p>
<blockquote>
<p>My text book says: "Magnetic quantum number describes the behavior of electron in a magnetic field. We know that the movement of electrical charge is always associated with magnetic field. Since the revolving ele... | g11515 | [
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<p>Today I was wondering about this situation. Let's imagine I have a circle of wire with a homogeneous section. I connect the wire with 2 terminals from ohmmeter. What minimum and maximum resistance can be measured? What resistance should I measure when terminals enclose an angle α with the center circle?</p> | g11516 | [
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<p>I do not understand how is $r^2 = x^2+y^2+z^2$ in spherical coordinate system. Can anybody give a simple derivation? I need to understand this in order to understand the lorentz transformation.</p> | g11517 | [
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<p>Bell-diagonal states are 2-qubit states that are diagonal in the <a href="http://www.quantiki.org/wiki/Bell_basis" title="bell basis">Bell basis</a>. Since those states lie in $\mathbb{C}^{2} \otimes \mathbb{C}^{2}$, the <a href="http://en.wikipedia.org/wiki/Peres%E2%80%93Horodecki_criterion">Peres-Horodecki criteri... | g11518 | [
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<p>How do I solve the speed of light in gravitational field?</p>
<p>Should I just add gravitational acceleration in speed of light?</p>
<p>$c'=c_0+g(r)t$?</p> | g11519 | [
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0.00965... |
<p>As we know from coulomb's law that:
$$\vec{E} = \frac{q}{4\pi\epsilon R^2} \hat{R}$$</p>
<p>using the above equation, how can I verify that:
$$\vec{\nabla}\cdot \vec{E}=\frac{q}{\epsilon}$$</p>
<p>I have tried to do it a home, but couldn't figure it out. Explicitly showing all steps would be very much appreciated.... | g327 | [
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<p>I am trying to choose the best approach to digitally analyse a signal, which is a mix of an unknown number (but less than 16) fundamental signals at specific frequencies (e.g., sines). </p>
<p>The goal is to determine which of the fundamental signals are present in the signal. </p>
<p>Some of the fundamental signa... | g11520 | [
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<p>I'm wondering if the Clebsch-Gordan series generalize to any orthonormal set of basis functions? If so, how would one go about deriving an expression for an arbitrary set of basis functions (perhaps an example derivation of the well known expression of spherical harmonics would be helpful)?</p>
<p>I know it has so... | g11521 | [
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<p>Let $\rho_{ABCD}$ be a sparse matrix of 4 systems each in a $d$-dimensional Hilbert space. </p>
<p>For $d<7$ in a reasonable time (few seconds) I able to perform the partial trace $\rho_{AD}$ using the code proposed in <a href="http://www3.imperial.ac.uk/people/m.tame/research">http://www3.imperial.ac.uk/people... | g11522 | [
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<p>Consider a problem in classical electrodynamics, when a monochromatic beam experiences total internal refraction when traveling from a medium with $n>1$ to a medium with refractive index $1$ - <a href="http://i.stack.imgur.com/2vXIy.png" rel="nofollow">see schematic below</a>. Using Fresnel equations one gets the... | g11523 | [
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<p>I've just now rated David Bar Moshe's post (<a href="http://theoreticalphysics.stackexchange.com/questions/551/how-does-one-geometrically-quantize-the-bloch-equations/553#553">below</a>) as an "answer", for which appreciation and thanks are given. </p>
<p>Nonetheless there's more to be said, and in hopes of stimula... | g11524 | [
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0.016... |
<p>How can we prove the following <a href="http://en.wikipedia.org/wiki/Cluster_decomposition_theorem" rel="nofollow">cluster decomposition formula</a></p>
<p>$$\langle \phi_1 \phi_2 \rangle ~=~ \langle \phi_1 \rangle \langle \phi_2 \rangle,$$</p>
<p>where brackets denote <a href="https://en.wikipedia.org/wiki/VEV" r... | g11525 | [
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0... |
<p>I'm currently studying an article by <a href="http://arxiv.org/abs/cond-mat/0506035">Maslov</a>, in particular the first section about higher corrections to Fermi-liquid behavior of interacting electron systems. Unfortunately, I've hit a snag when trying to understand an argument concerning the (retarded) self-energ... | g11526 | [
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<p>The law that</p>
<p>$$\frac{d\vec{L}}{dt}= \vec{T}$$</p>
<p>where $\vec{T}$ is torque about a frame's origin $o$ and $\vec{L}$ is the angular momentum about that origin $o$. </p>
<p>Can this law be ultimately (always?) traced backed to Newton's Second Law ?</p> | g11527 | [
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0.04734154790639877,
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<p>The definition of a classical black hole is when even electromagnetic radiation can not escape from it. Why then can <a href="http://en.wikipedia.org/wiki/Hawking_radiation" rel="nofollow">Hawking radiation</a> be emitted from semi-classical black holes?</p>
<p>What is difference between Hawking radiation and elec... | g367 | [
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<p>I'm trying to understand this image of a particle tracing experiment (which can be found all over the net if you <a href="https://www.google.com/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1194&bih=960&q=particle+collision&oq=particle+collision&gs_l=img.3..0l10.2086.6479.0.6774.18.... | g11528 | [
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0... |
<p>If I have, for example a particle with $s = 3/2$ and $\ell = 2$, what are the allowed values of $j$?
I'm slightly confused because I know that $j = \ell + s$, so surely there is only one allowed value?</p> | g11529 | [
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<p>When doing electron diffraction on graphite (a popular experiment for students at universities) always diffraction at these two planes with distances $d_1$ and $d_2$ are observed:</p>
<p><img src="http://i.stack.imgur.com/dhKLG.png" alt="enter image description here"></p>
<p>But a plane parallel to the ones with d... | g11530 | [
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-0.0... |
<p>I am referring to <a href="http://arxiv.org/abs/1306.5242" rel="nofollow">this paper</a>. </p>
<p>I guess that in this paper one is trying to relate the massless spin $s$ gauge fields in $AdS_4$ to conformal spin $s$ theory on $S^3$. </p>
<ul>
<li><p>So am I right that the operator $K$ that has been defined here i... | g11531 | [
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<p>More precisely, how small is the potency a listener hears, compared to the potency of the emitter.</p>
<p>I'd like to present a simple and yet reasonable approximation, to a high school audience (I am a teacher)</p>
<p>Intuitively, it should decrease with a square (of distance; because of the expansion of the area... | g11532 | [
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0.07... |
<p>AFAIK Glass is insulator, it doesn't have free electron. It's said metal is a good conductor of heat because it has free electron, glass doesn't have free electron, why it is a good conductor of heat?</p> | g11533 | [
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<p>Let's say I have a ceramic slab on a conveyor belt that is initially at $450\,^{\circ}\mathrm{C}$ and there is air being blown over it at a speed of $35 \frac{m}{s}$ with an ambient temperature of $18\,^{\circ}\mathrm{C}$ until the slab reaches a temperature of $35\,^{\circ}\mathrm{C}$.</p>
<p>I understand the over... | g11534 | [
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<p>Long storage times for qubits will be integral in the construction of a scalable quantum computer. This leads me to ask the current state of affairs in our ability to store qubits. Namely, what is the <strong>record</strong> storage time for a qubit at <strong>any</strong> temperature? </p>
<p>Upon searching for th... | g11535 | [
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<p>Does a large thick wire that has over 1000 amperes of current flowing
through it generate powerful magnetic fields? </p>
<p>What formula is best here to predict $B$?</p> | g368 | [
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0.01015818677842617,
-0.03553275763988495,
0.0569143071770668,
-0.051881343126297,
-0.006063139... |
<p>I am not doing a physics degree but an engineering degree but i am planning using my free time to self study all the math in preparing myself to self study subjects in theoretical physics. (I've always wanted to do theoretical physics but there are no scholarships offered in my country for the subject and my family ... | g108 | [
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<p>My 'government-issued' book literally says:</p>
<blockquote>
<p>Energy is the capacity to do work and work is the product of net force and the 1-dimensional distance it made a body travel while constantly affecting it.</p>
</blockquote>
<p>I didn't want to say it, but what!?</p>
<p>Seriously though; why does <a... | g11536 | [
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<p>The most recent discussion of what axioms one might drop from the Wightman axioms to allow the construction of realistic models that I'm aware of is <a href="http://dx.doi.org/10.1088/0034-4885/38/7/001">Streater, Rep. Prog. Phys. 1975 <strong>38</strong> 771-846, "Outline of axiomatic relativistic quantum field the... | g11537 | [
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<p>I would like to understand the mathematical language which is relevant to instanton moduli space with a surface operator.</p>
<p>Alday and Tachikawa stated in 1005.4469 that the following moduli spaces are isomorphic.</p>
<ol>
<li>the moduli space of ASD connections on $\mathbb{R}^4$ which are smooth away from $z_... | g11538 | [
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<p>I'm especially interested in elegant illuminating proofs which don't involve a lot of straightforward technical computations</p>
<p>Also, does a non-perturbative proof exist?</p> | g11539 | [
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<p>By now, there has been enough grasp on quantum chaos for systems with a small number of degrees of freedom. The major tool used is periodic orbit theory to approximate the spectral distribution. Is there any suitable generalization to a quantum field theory with one spatial dimension whose classical analog exhibits ... | g11540 | [
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<p>In terms of gravity and electric fields, I'm not sure what the difference is between field strength and potential is and how they are related? Both using maths and not.</p> | g11541 | [
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<p>Where can I find a way to construct the hamiltonian of a water molecule bounded to a surface? More generally,how can one write the hamiltonian of an atom bounded to a surface?</p> | g11542 | [
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<p>When you hear about <a href="http://en.wikipedia.org/wiki/Atomic_clock" rel="nofollow">atomic clocks</a>, it's accuracy is described by saying something like, " it neither gains or loses $x/y$th of a second in $z$ years." How is this error calculated? Does an error imply that we have a more regular physical phenomen... | g11543 | [
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<p>I was reading about <a href="http://en.wikipedia.org/wiki/No-cloning_theorem">no cloning theorem</a> and it arose a thought experiment, if there were a way of compare quantum states (for being equal) then you could build a pseudocloning machine that searches for quantum states till it finds an equal state, so I thin... | g11544 | [
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<p>Given a closed chain with a total length of 1.2m rotating at 1'800 rpm and a total mass of 0.4kg, what is the drag force pulling on one chain link?</p>
<p>I originally thought that since no link size was given I need to assume the link sizes to be infinitely small. Thanks to the answers below I now know this won't ... | g11545 | [
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<p>I've seen several video which claims that is <a href="http://en.wikipedia.org/wiki/Anti-gravity" rel="nofollow">anti-gravity</a>. I am sure at least one of them, use a kind of electricity to lift an object! (triangle lifter), I would guess electricity lift that object by air. But what is the equation?, I have no ide... | g11546 | [
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<blockquote>
<p><strong>Question</strong>: How to <strong>classify/characterize the phase structure of (quantum) gauge theory</strong>?</p>
</blockquote>
<p>Gauge Theory (say with a gauge group $G_g$) is a powerful quantum field theoretic(QFT) tool to describe many-body quantum nature (because QFT naturally serves f... | g11547 | [
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<p>I am trying to understand the <a href="http://www.google.com/search?q=landauer+approach" rel="nofollow">Landauer approach</a>. Consider the setup: (left contact)-(conductor)-(right contact). For simplicity, the conductor is a 1d wire (the transverse part is not relevant for this question). The eigenstates of the con... | g11548 | [
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<p>I want to consider a thought experiment. Lets ignore technical problems of actually performing such an experiment.
Consider two photons having the same wavelength. We send 1 photon to a distant galaxy (millions of light years away). The photon would hit a mirror there and return to Earth. On Earth (I assume) a cosm... | g11549 | [
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<p>Since $\text{force = mass}\times\text{acceleration}$,</p>
<ol>
<li><p>is it right to say that an object traveling at a high
constant velocity (zero acceleration), exerts zero
force upon impact with a stationary object?</p></li>
<li><p>I understand that upon impact, the projectile
decelerates rapidly from initial ve... | g11550 | [
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<p>If you were to upload our bodies onto a computer. Exactly how much storage would we take up?</p> | g11551 | [
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<p>Somewhere in a two dimensional convex bulk of particles (pic related) on a random position a reaction takes place and a particle is sent out in a random direction with a constant velocity $v$. </p>
<p>What is the average distance such a particle travels until it leaves the bulk?</p>
<p><img src="http://i.imgur.com... | g11552 | [
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... |
<p>Let us assume that a person moves at the speed of light say towards a planet -say Neptune. Neglecting the relativistic mass effects of the person, what would be his perception?
In Vsauce- a YouTube channel, in "travel inside a black hole " video, he describes that the field of view would be enormous since he can pe... | g11553 | [
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<p>I have some questions about the excluded volume parameter :
1. What is the definition of the excluded volume parameter , or how could I describe the excluded volume of a polymer system？
2. What is the excluded volume parameter of homopolymer without solvents? Is it the same as the case in athermal solvents?
Thank yo... | g11554 | [
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<p>Can the collapse of a quantum mechanical state in general into one the eigenstates of an observable whenever its measurement is made written mathematically? If yes, how?</p> | g11555 | [
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<p>In one of the two main theoretical approaches used in describing ultracold Fermi gases and the BEC-BCS crossover, the so-called BCS-Leggett approach, the starting point is the BCS trial wavefunction:</p>
<p>$$ \mid BCS \rangle \equiv \prod_{\mathbf{k}} \left( u_{\mathbf{k}} + v_{\mathbf{k}} P^\dagger_{\mathbf{k}} \... | g11556 | [
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<p>I have been thinking about something thing... </p>
<p>I want to attach four or any number of magnets with arms to an axle..</p>
<p><img src="http://i.stack.imgur.com/VLEnx.png" alt="enter image description here"> </p>
<p>Blue dots be magnets.</p>
<p>Its is not a wheel configuration, all arms can move independent... | g11557 | [
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<p>My friends and I are designing a bench press spotter. Essentially, when the user needs help lifting the barbell due to muscle fatigue, an arm on each side of the user raises to provide assistance. These arms are essentially cantilever beams. We determined that a rectangular beam would experience the least amount of ... | g11558 | [
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<p>Consider an experiment that produces photons in an entangled state such as $1/\sqrt{2}(|{H,H}\rangle+|{V,V}\rangle)$. The photons are in a superposition of horizontal and vertical polarization, and the way we analyze this is to say that the photons are in <strong>both</strong> states at the same time. Though this i... | g11559 | [
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<p>Below is an excerpt from a physics textbook:</p>
<blockquote>
<p>One common way to charge a capacitor is to connect these two wires to opposite terminals of a battery. Once the charges $Q$ <strong>and</strong> $-Q$ are established on the conductors, the battery is disconnected. This gives a fixed potential differ... | g11560 | [
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0.01290799118578434,
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0.01... |
<p>Some cubic thermodynamical equations of state predict <a href="http://en.wikipedia.org/wiki/Pressure#Negative_pressures" rel="nofollow">negative pressures</a>, have negative pressures any physical meaning? Could they be related to <a href="http://en.wikipedia.org/wiki/Negative_mass" rel="nofollow">negative mass</a>?... | g11561 | [
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<p><img src="http://i.stack.imgur.com/s2KzU.png" alt="enter image description here"></p>
<p>The picture is just for example. I don't know why $i$ and $i_1$ have different directions and $i+i_1=0$ according to KCL. Also, the value of voltage at each element. I mean in why the $V$ of the end of $R_1$ is negative but the... | g11562 | [
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<p>"If a wire loop is completely in magnetic field no current is induced as voltage induced is balanced by an equal and opposite voltage. "</p>
<p>My guess for this statement is that the loop wire must be stationary and that voltage is zero if its equal on both sides of the wire
my question is if current will stil be ... | g11563 | [
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<p>My question has an inclined plane of mass $M$ and simple block kept on it, of mass $m$ (Both on a table). All surfaces are friction-less. Both of the objects would move, block down the incline and inclined plane parallel to the table, somewhat opposite to the block. Can the two equations I make be from the Free Body... | g11564 | [
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<p>In the definition of the electrical field we use the concept of a test charge because we state that the point charge is required for the direct application of the Coloumb's Law and its infinitesimal small magnitude ensure that it does not distort the actual field that we intend to measure. But once the electrical fi... | g11565 | [
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0.... |
<p><em>NOTE: Because this was a long question I have split it up in two different questions!</em></p>
<p>For a course on quantum integrability I am reading <a href="https://people.sissa.it/~ffranchi/BAnotes.pdf" rel="nofollow">these</a> notes.
(Franchini: Notes on Bethe Ansatz Techniques. Lecture notes (2011))</p>
<p... | g11566 | [
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<p>We all know the explanation videos and other material using the water waves analogy to illustrate the propagation of electrons or photons and the interference patterns measured in the the single-slit and double-slits experiments.</p>
<p>Being just an analogy it misses for sure many attributes by which light/electro... | g11567 | [
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0.0517... |
<p>In QED and the basic Higgs mechanism, there is a local gauge transformation where a scalar field $\phi$ is transformed as:</p>
<p>$e^{i\theta\eta(x)} \phi$ </p>
<p>The partial derivative of this however makes the above not
invariant, and so a covariant derivative is introduced in this way:</p>
<p>$D_\mu e^{i\the... | g11568 | [
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<p>Say I am measuring a quantity $x$ in physical system whose true value is approximately sinusoidal in time. I have an instrument to sample this quantity, for which the manufacturer gives an accuracy spec. Can I use this accuracy spec $(\Delta x?)$ to compute the uncertainty of the sample mean $\bar{x}$ of the quantit... | g11569 | [
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-0.... |
<p>Wolf's paper <a href="http://nzaier.com/nzaierbb/system/upload_files/Physica1985_wolf_LyapunovExpo.pdf" rel="nofollow">Determining Lyapunov Exponents from a Time Series</a> states that:</p>
<blockquote>
<p>Experimental data typically consist of discrete measurements of a
single observable. The well-known techni... | g11570 | [
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... |
<p>In Weinberg's book <em>The Quantum Theory of Fields, Volume 1</em> on p.388 (Chapter 9), the following identity is used (with f being any "reasonable" function):</p>
<p>$$f(+\infty) + f(-\infty) = \lim_{\epsilon \rightarrow 0^+} \epsilon \int_{-\infty}^{+\infty} d\tau f(\tau) e^{-\epsilon |\tau|}.\tag{9.2.15} $$</p... | g11571 | [
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<p>Some phenomena in physics defy intuition. Others have very intuitive explanations which you could explain easily to a layman. Sometimes, these intuitive explanations are simply wrong.</p>
<p>What phenomena in physics have intuitive, but totally wrong, explanations? An explanation you could use to easily convince yo... | g11572 | [
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0.0... |
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