Questions tagged [electromagnetism]
The classical theory of electric and magnetic fields, both in the static and dynamic case. It also covers general questions about magnets, electric attraction/repulsion, etc. Distinct from electrical-engineering.
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existence of other forces obeying inv square law
Is there any restriction in what we know of physics to the existence of other type of forces that obey the inverse square law in 3 dimensions.
I mean other than electromagnetic and gravitational.
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Does the wavelength always decrease in a medium?
I was studying a GRE Physics Test problem where optical light with a wavelength of 500 nm travels through a gas with refractive index $n$.
If we look at the equations for wave motion and index ...
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One point to change electric field
Can there be a charge configuration in space such that at any instant of time I can change the electric field at one and only one point?
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Photons in a "wrap-around" universe
This question was inspired by: How are photons "consumed"?
Imagine I have some number of photons, $N$, each of frequency $\nu$, moving randomly in a spherical "wrap-around" universe of ...
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Practical physics: where does this current come from?
It's been a while since school and I don't remember the right laws and formulas. So I come here. :)
I've got a power cord extender running from the wall outlet to my washing machine. It's about 3 or ...
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Singularity-free stationary electro-vacuum solution
Let's say we have a spherically symmetric fluid:
$$
T^{\alpha \beta} = \begin{bmatrix}
\rho & 0 & 0 & 0 \\
0 & p & 0 & 0 \\
0 & 0 & p & 0 \\
0 ...
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3 current loops with non-conservation of momentum, when one specifically considers SIGNs
Thought experiment I.
Consider two loops of wire, 2 small dipoles B and C , with a common axis z (facing each other) and (say) 30 cm apart B to C. At the speed of light, information (including a ...
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2 electromagnetic loops, with light-speed constraints: Is Newton's Third Law violated?
I'm a retired Physics Professor, but I admit I'm puzzled by this...
Consider two loops of wire, 2 small dipoles B and C , with a common axis z (facing each other) and (say) 30 cm apart B to C. At ...
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Why and how exactly is electric motor torque limited?
Inspired by this question and specifically this answer to it.
From my experience there's always some very specific limit to how much torque an electric motor can output. For example, an electric ...
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Creating the opposite of an optical lattice
Is it possible to create periodic potentials that instead of creating a well for an atom to be trapped in, repulsed by that specific location?
If yes, can we use this as a means to make artificial ...
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The feeling of fuzz on the display surface of a Cathode Ray Tube Television
I was always wondering where the feeling of fuzz comes from when touching a CRT (Cathode Ray Tube) television on its display screen when the TV is turned on. Can someone please explain why I feel ...
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How is a spherical electromagnetic wave emitted from an antenna described in terms of photons?
When an atenna transmits radiowaves isn't it true that the electromagnetic pulse is radiated away from the accelerating electron as a spherical wave in all directions simultaneously, and if so how can ...
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What effect would liquid air have on a resonant coil?
This description of Tesla's "magnifying transmitter", which supposedly used electrical resonance to transmit energy (similar to resonant inductive coupling?) states that the coils (or at least part of ...
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Are Classical Field Theory and Quantum Mechanics of a single particle (nonrelativistic or "classical") limits of Quantum Field Theory?
Recently I talked about QFT with another physicist and mentioned that the Quantum Field Theory of a fermion is a quantisation of its one-particle quantum mechanical theory. He denied this and ...
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fraction of magnetic energy stored outside a solenoid
If I have a long solenoid, e.g. length $l$ and radius $r$ with $l = kr$, where k >> 1, with a nonpermeable (e.g. air) core, how much of the magnetic energy is stored outside as compared to inside?
If ...
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