# Tag Info

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Suppose you start with a linear solenoid. Due to the Lorentz force charge particles travel in circles (or helices) inside the solenoid so they can't reach the walls of the solenoid. But obviously the trouble is that they will leak out of the ends. Now we curve the solenoid round and join its ends together to make a torus so now the particles can't leak out ...

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The words ultimately refer to the same "objects" but they describe different aspects of them. "Permanent magnets" are objects and they're defined by the external property (what they look like from outside) that the magnetic field remains nonzero around these objects without any activity. On the other hand, "ferromagnets" are materials and the focus is on ...

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Below I'll use Planck units, for which, in particular, $c = \epsilon_{0} = =1$. In fact, the full system of Maxwell's equations provides the statement that the only two vector components of the EM field $\mathbf E, \mathbf B$ are independent (in general, due to a deep symmetry reason, namely that a massless particle has only two polarizations). Next, if we ...

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Comments from @aquirdturtle have led me to rewrite my answer and to realise that it was a question worth asking. @ACuriousMind has likened the situation to a mass falling on the Earth. In that case the mass and Earth system loses gravitational potential energy and they both gain kinetic energy although almost all of it resides with the mass. Carrying on ...

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This sticker is indicating caution when you heat a liquid. Microwave can lead to superheater water which can be dangerous. If your water is superheated, it may not explode/boil over until an object is placed inside the water (e.g. a spoon). One way around this is to place a chop stick or object into the water while it is heating. This will prevent that ...

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The helicopter and the power lines are at different potentials, the difference being so great as to cause the air in between to become a conductor. If you applied such a potential difference across a line worker it would probably result in death. You will note that the line worker is holding a metal stake which has a "pointed" end. This increases the ...

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Electromagnetic (EM) radiation between 400nm and 700nm in wavelength is the same thing as light. There is no difference. Neither is there a distinct difference between light, ultraviolet, x-rays, gamma rays, infrared, microwaves, or radio waves. Those names are all just human convention to specify EM radiation in certain frequency ranges. And regardless ...

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That is not the energy density of the electromagnetic field. That is the energy flow density vector of the field, also known as the Poynting vector. Energy flows in some direction, so its density must be a vector. You're totally right, energy density is not a vector, and it is given in gaussian units as $$\mathcal{E}=\frac{1}{8\pi}\ (E^{2}+B^{2})$$ As ...

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In your last question it is important as to what you mean by WRT the question. If you are trying to find the E-field due to a point charge using Gauss then to make the surface integration easier you choose a surface which has the following properties: the E-field direction is everywhere perpendicular to the surface the E-field has a constant ...

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Let's assume the magnetic field vectors point in z-direction (or: let's call the direction the magnetic field vector points "z"). Then we have for the magnetic field: $$\vec{B} = \begin{pmatrix}0\\0\\B\end{pmatrix}$$ and for the speed of the electron: $$\vec{v} = \begin{pmatrix}v_x\\v_y\\v_z\end{pmatrix}$$ The Lorentz-force $\vec{F}$ due to a magnetic ...

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The reason to use the alloy is because it has a much higher resistivity than copper and so the alloy wire will have a higher resistance which with standard laboratory apparatus can be measured more accurately. I also seem to remember that the temperature of coefficient is lower for some of these alloys ie for a given increase in temperature the resistance ...

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There is actually a very simple answer to this question: The absolute number of turns which each of the transformer winding should have (with fixed turns ratio) depends entirely upon which voltage and current ratings the transformer is intended to be used for. Let me explain. For instance, measurement transformers for high voltages typically have a ...

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I'm going to say no, because I interpret a "physical entity" as something which we can observe, and therefore confirm it's existence. For instance: Particles (0 dimensional): Mathematically are points, but when we observe them we observe them to have sizes because of the observation process (bouncing photons off atoms, electrons off other electrons, even at ...

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Do any physical real entities exist? All the particles we consider elementary (the most well-known being the electron) do not occupy any finite amount of space, i.e. are pointlike, at least according to our present understanding of the standard model. However, that understanding could change as new theories emerge or as experimental evidence is found. As ...

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I think I have a proof for you (though you may find it unsatisfying). For the most part, I'm following the proof on the wikipedia page you link to. I do avoid the dirac delta function however. Starting from the Biot-Savart law: \mathbf{B}(\mathbf{r})=\frac{\mu_0}{4\pi}\int_V ...

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Trackpy is a Python package for particle tracking in 2D, 3D, and higher dimensions. http://soft-matter.github.io/trackpy/stable/ https://github.com/soft-matter/trackpy The Matlab Particle Tracking Code Repository Daniel Blair and Eric Dufresne http://site.physics.georgetown.edu/matlab/ Particle tracking using IDL John C. Crocker and Eric R. Weeks ...

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The basic principle: 1 volt is induced in a loop when the magnetic flux through the loop changes at a rate of 1 weber per second, i.e. 1 tesla times square meter per second. Provided you have a 1x1 cm loop, in a 0.5 T field of a pair of very strong neodymium magnets, and the loop has 100 turns, the overall magnetic flux through all the coil turns would be ...

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