General > General Technical Chat
Veritasium -- How Special Relativity Makes Magnets Work.
penfold:
--- Quote from: aetherist on April 09, 2022, 09:08:17 pm ---[...]
But, ignoring AC, ignoring wires, ignoring pulses – has a magnetic field ever been measured around an electron beam?
Here i am thinking an electron beam in a long glass tube.
--- End quote ---
Please (for your own sake) tread cautiously on this one, regardless of whether you approach it from a relativistic or pure-Maxwell, you must remember that there is an entire loop of circuit to consider. Remember that the total force on a charge (having velocity) near a beam of electrons is, in a Maxwellian sense, the sum of the forces due to the magnetic "field" and electric "field" whereas in the relativistic sense it is the total electric force from the charge's perspective. It adds up to the quantity in both cases, but it is not a simple sum to do in your head. In either case, it is an important distinction between, philosophically, whether you are considering the field, force or trajectory in, of, or around the beam.
TimFox:
The probe coils used in electron-beam accelerators are shielded against electrostatic fields, and sense the magnetic field induced by the current passing through the center of the coil.
penfold:
Ahh, yes, but the sheild must be transparant to the relativiistic effects as there is no relative motion wrt the fixed charges of the sensor of those of the hard-wired "fabric" elements of the electron beam's circuit... I think... its a bit late for me to be thinking about reference frames.
If the shield were a rotating disc or a cylinder rotating about an axis that intercepts that of the electron beam (but not parallel to and the geometry of the cylinder allowing passage of electrons through), the continuous motion of the cylinder (or disc) with facets of it passing through an apparently varying electric field (seeing, relatively, a non-linear beam current), the constant redistribution of charges would constitude a current visible in all reference frames... which might make an aetherist's head explode (the rate of redistribution being higher than drift velocity), but might make for an alternative interpretation of the Faraday disc.
aetherist:
--- Quote from: penfold on April 09, 2022, 11:37:28 pm ---Ahh, yes, but the sheild must be transparant to the relativiistic effects as there is no relative motion wrt the fixed charges of the sensor of those of the hard-wired "fabric" elements of the electron beam's circuit... I think... its a bit late for me to be thinking about reference frames.
If the shield were a rotating disc or a cylinder rotating about an axis that intercepts that of the electron beam (but not parallel to and the geometry of the cylinder allowing passage of electrons through), the continuous motion of the cylinder (or disc) with facets of it passing through an apparently varying electric field (seeing, relatively, a non-linear beam current), the constant redistribution of charges would constitude a current visible in all reference frames... which might make an aetherist's head explode (the rate of redistribution being higher than drift velocity), but might make for an alternative interpretation of the Faraday disc.
--- End quote ---
A DC beam in a long glass tube would be simpler.
But the spinning disc or cylinder reminds me of Kennard's version of the Faraday disc X where Kennard shows a falsification of the STR explanation for mmf around a current carrying wire.
http://www.conspiracyoflight.com/Kennard.pdf
Attached below are pages of Kennard's 1912 paper.
penfold:
--- Quote from: aetherist on April 11, 2022, 10:22:56 pm ---
--- Quote from: penfold on April 09, 2022, 11:37:28 pm ---Ahh, yes, but the sheild must be transparant to the relativiistic effects as there is no relative motion wrt the fixed charges of the sensor of those of the hard-wired "fabric" elements of the electron beam's circuit... I think... its a bit late for me to be thinking about reference frames.
If the shield were a rotating disc or a cylinder rotating about an axis that intercepts that of the electron beam (but not parallel to and the geometry of the cylinder allowing passage of electrons through), the continuous motion of the cylinder (or disc) with facets of it passing through an apparently varying electric field (seeing, relatively, a non-linear beam current), the constant redistribution of charges would constitude a current visible in all reference frames... which might make an aetherist's head explode (the rate of redistribution being higher than drift velocity), but might make for an alternative interpretation of the Faraday disc.
--- End quote ---
A DC beam in a long glass tube would be simpler.
[...]
--- End quote ---
That it would, but would it really show anything interesting?
The reason I suggested the off-axis rotating sheild is that it doesn't rely on metal-metal sliding contacts, so it is an experiment that may (or may not) operate on a similar underlying principal as the classic Faraday disc, but has a very different physical makeup and so relys on different sources of error and discrepancy.
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