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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.

5
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analysis, in pure electromagnetism the truly fundamental thing is, in a sense, charge. Charge produces electric field, and therefore also produces voltage differences. Moving charge, a.k.a current, produces magnetic field. …
answered Aug 4 '15 by DanielSank
3
votes
Physically, this happens because a changing current generates a voltage which tries to push the charges in the direction they're already moving. When you shut off the power supply, the current in the …
answered Oct 15 '15 by DanielSank
3
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Definition of dB Fist we must understand the meaning of "dB". The symbol "dB" means "decibel" and is la dimensionless unit of measure. Given a quantity $N$, the value in the dB scale is $$N_\text{dB …
answered Aug 9 '15 by DanielSank
1
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Lenz's law tells you that the coil will act to try to keep the magnetic flux constant. You're removing a magnet bar with the north pole on the right, so the coil will try to produce a magnetic field t …
answered Oct 28 '14 by DanielSank
2
votes
Typically when we refer to more complicated currents than pure DC or sinusoidal AC, we refer to them as having a "DC component" and AC components of various frequencies. As far as I know, the DC co …
answered Mar 23 '18 by DanielSank
6
votes
One of Maxwell's equations is $$ \nabla \times \vec{E} = - \frac{d\vec{B}}{dt} \, .$$ Consider an imaginary disk whose normal vector is parallel to the axis of the coil and which is inside the coil. I …
answered May 8 '15 by DanielSank
2
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Yep, that's it exactly. If you have a large enough magnetic field present when the superconductor is cooled through it's critical temperature $T_c$, then the flux can be trapped instead of expelled. …
answered Apr 16 '17 by DanielSank
67
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Can tin foil hats actually block anything? Anything? Sure. As already noted by Daniel Griscom's answer, tin foil can block several "things" including rain, alpha rays, and electromagnetic radiati …
answered Sep 23 '15 by DanielSank
4
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quantization of charge. Finally, note that in fact our known theory of electromagnetism does work if we add in magnetic monopole terms (i.e. magnetic charge and current) as long as we also put in the …
answered Dec 3 '18 by DanielSank
4
votes
The axes definitely matter. If you put light through a linearly polarized glass pane, the output light will be entirely polarized along the polarization axis of that pane. The intensity of the output …
answered Mar 25 '14 by DanielSank
1
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Does this mean that there are two different fields, one static field and one induced by a laser? Yes, that is exactly right. There is a static (meaning not time dependent) electric field $\vec{E} …
answered Aug 7 '15 by DanielSank
5
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The "field" term describes electromagnetic waves moving around in space-time, and that's it. It only describes electromagnetic fields (the $F$ tensor), no charged particles and therefore no sources of …
answered Jan 31 '15 by DanielSank