Tagged Questions

The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

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Fleming's right hand and left hand rule

Why are there two rules: Fleming's left hand and right hand rules? What is the difference between the two and why can't we use just one rule? Suppose the magnetic field is from right to left and ...
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Why is the Mixed Faraday Tensor a matrix in the algebra so(1,3)?

The mixed Faraday tensor $F^\mu{}_\nu$ explicitly in natural units is: ...
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Verification of Lenz's law in magnetic induction

So the device is a Galvanometer. According to the Lenz's Law, when we take the magnet towards the coil, the pole at the right end, should be north pole and when we take it away, the pole should be ...
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Why is Kirchhoff's second law commonly used for circuits involving inductivity?

I have often seen in introductory literature, e.g. for the activation process of a circuit with a power source which delivers the voltage $U$, current $I$, resistance $R$ and an inductivity $L$, that ...
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Do you know any graphing software for graphing equipotential lines? [closed]

well, do you know any software for graphing equipotential lines? I only know how to graph straight lines :( Thanks for any information.
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$\vec{E}$-and $\vec{B}$-fields in RCL circuit

Consider a basic RCL-Circuit consisting of an ideal resistor, an ideal capacitor and an ideal inductor in series. Assume that at time $t = 0$ the current is zero and the capacitor is charged with ...
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Intuitive definition of electromagnetic field

I am curious about the following: Checking about what is an EM field in wiki it says: An electromagnetic field (also EMF or EM field) is a physical field produced by electrically charged ...
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Why are GPS transmitting signals made so weak?

Twice this year, my car's GPS receiver got totally lost. It seemed the cause of this was heavy cloud, (because I can't think of any other reason), and the GPS stayed in "Recalculating" mode, until ...
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Experiment measuring vacuum permittivity and permeability in high speed

Suppose that we do NOT know anything of constancy of speed of light, to say nothing of special relativity. It is that we acquired a constant speed of light from Maxwell's Equations that we finally ...
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Motion of electron and proton in semi infinite magnetic field? [closed]

An electron and a proton are moving on straight parallel path with same velocity. They enter a region of semi infinite magnetic field perpendicular to velocity. What will happen there? Will both of ...
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Why is there longitudinal conductance in a partially-filled Landau level?

Suppose I consider an infinite, non-interacting (so no FQHE should happen) 2DEG in the magnetic field $\vec B=B\hat z$ with a non-integer filling factor, say 0.13 or whatever. Suppose I apply an ...
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What makes B-field not be arbitrarily large very close to an electric conductor?

Assume an inifinitely long, straight thin electrical conductor with current I. It follows from Ampere's law that the B-field intensity is proportional to 1/r, where r is the distance from the ...
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How to determine the angular velocity of a particle with mass $m$ and charge $q$ in a constant B field? [closed]

$\textbf{PROBLEM:}$ A particle with mass $m$ and charge $q$ moves in a constant magnetic field $B$. Show that, if the initial velocity is perpendicular to $B$, the path is circular and the angular ...
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Is the electrostatic field really static? Does thermal vibrations not affect it?

We know that if a conductor has any net charge, the charges reside on the surface. The electric field immediately outside the surface is perpendicular to the surface. But the charged particles, say ...
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How is ampere defined for alternating current?

Both alternating current and direct current are measured in ampere. But how is ampere defined for alternating current? It cannot be defined from two mutual attraction of two parallel wires carrying ac ...
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Water flow in salt solutions contemporary exposed to an electrical and constant magnetic field

When a permanent magnet is held motionless close to a salt solution which already has been exposed to an electrical field a flow in the water will be induced and can be detected by applying some ...
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Why can xenon gas stay ionised after the “trigger voltage” is removed?

From my understanding of a Xenon flash circuit, a storage capacitor and a trigger capacitor are charged up to about 240V (both with similar RC values, but less capacitance is needed for the trigger ...
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Trying to give a (non-rotating) black hole an electric dipole

Suppose there is a Schwarzschild black hole. You add positrons to the north "pole" and electrons to the south "pole". From an external observer, objects that you add end up "stuck" to the horizon. ...
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Do relativistic electrons have more charge?

Gauss's law tells us that the total electric flux out of a closed surface is equal to the charge enclosed divided by the permittivity. When a charged particle is moving close to the speed of light ...
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Why don't photons split up into multiple lower energy versions of themselves?

A photon could spontaneously split up into two or more versions of itself and all the conservation laws I'm aware of would not be violated by this process. (I think.) I've given this some thought, and ...
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Electric field radiation with moving charge and observation point

I've been working on Chapter 34 of the first volume of the Feynman Lectures on Physics http://www.feynmanlectures.caltech.edu/I_34.html#Ch34-S1. In Fig. 34–3 (reproduced above) Prof. Feynman shows ...
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What is the role of the Cowling, Pedersen and Hall resistivities (or conductivities) in plasma physics?

The current density $\vec{j}$ can be computed as $\vec{j} = \vec{\vec{\sigma}} \vec{E}$, where $\vec{\vec{\sigma}}$ is the conductivity tensor and $\vec{E}$ is the electric field. This conductivity ...
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Why do electrons and positrons exhibit opposite helical motion in a magnetic field?

When you throw an electron through a solenoid, it moves helically around the field lines, as per this schoolphysics illustration: © Keith Gibbs 2013 Then if we were to throw a positron through the ...
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Dyon condensation and generalized Meissner effect

In section 2.B of Metlitski and Vishwanath's paper: "Generally condensation of a dyon with charges $(q,m)$ gives rise to an analogue of a Meissner effect for the gauge field combination ...
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Physics of color: why do visible colors absorb all colors except the color itself?

It's funny I cannot answer this question, but I really don't have a very good physical intuition for how color works. I know that sunlight and (say) light from lightbulb is a superposition of all ...
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Showing that the magnetic field inside an infinite current carrying cylinder is zero

I'm doing some self studying of introductory physics, and was working a question from a textbook that has several parts. The first few parts asked me to show that the magnetic field of an infinite ...
The electric field due to charge is $E=\frac{Q}{r^2}$. Why is the curvature in spacetime produced by this electric field so small? Let's say we want to calculate curvature(in spacetime) produced by ...