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Veritasium -- How Special Relativity Makes Magnets Work.

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TimFox:

--- Quote from: aetherist on April 13, 2022, 12:47:34 am ---
--- Quote from: TimFox on April 12, 2022, 09:20:53 pm ---Once again, you are wrong.  The diagnostic equipment and beam testing procedures that I suggested you read clearly show that the magnetic field outside a beam of charged particles is identical to that outside a wire.
In a particle accelerator, one can compare the current with these magnetic sensors to the current that hits a Faraday cup (which suppresses the effect of secondary emission from the target).
Have you ever seen a particle accelerator, or read anything about them?
What do your countrymen at the Australian Synchrotron Lab say?

PS:  doing some elementary Googling, I found an interesting engineering thesis from Georgia Tech back in 1962:  https://smartech.gatech.edu/bitstream/handle/1853/14924/lineberger_william_c_196212_ms_69818.pdf?sequence=3&isAllowed=y 
The author discusses practical methods for measuring the magnetic field induced by a beam of charged particles without interrupting the beam.  Since this was already a physical phenomenon applied to practice in engineering, no one needed to crow about it.
--- End quote ---
But, if the magnetic field of a steady DC electron beam in vacuo (in a glass tube) is equal to the magnetic field of the wire supplying the steady DC, then this falsifies the STR explanation (ie that it is due to the length contraction of the wire), because there is no wire for the electron beam, there is only vacuum.
The vacuum contains spacetime, & i suppose that Einsteinists could claim that the space of the spacetime contracts, but that would i think require that the electrons spacings also contract, which would give the beam a double dose of negative charge, which is the opposite of what Einsteinists are looking for.

--- End quote ---

Your logic here is fallacious.
1.  It is well-established experimentally that current through a wire and current in a beam of charged particles induce a magnetic field B, according to the law of Biot and Savart that is later incorporated into Maxwell's Equations.
2.  Purcell published an explanation for a particular common case of current flowing through a metallic conductor, where the substantial magnetic field is induced despite the wire being electrically neutral.  There is some controversy about his derivation, some of which suggests that it is only useful as a pedagogical explanation.  However, quantitatively, it agrees with experiment.  He did not discuss this as an explanation for other situations of current, although he does say elsewhere in his textbook that there are other forms of current besides that in a wire.
3.  The case of a charged particle beam is a different configuration, since the beam itself is not electrically neutral and the velocity can easily be "relativistic" or "very relativistic" for an electron beam at a reasonable kinetic energy, while the drift velocity in Purcell's explanation is not so large.
4.  The experimental evidence for case 3 does not refute case 2, since the basic situations are different but the current is the same.

I can make fun of your logic with this analogy:
1.  Visible light is that portion of the electromagnetic spectrum that can be sensed by human vision.
2.  A common source of visible light is an incandescent light bulb, where current through the filament heats it to incandescence and much of the electromagnetic radiation emitted by the hot filament is visible.
3.  Another source of visible light is bioluminesence, produced by chemical processes within a living organism.  There is no external source of electricity to the firefly, and the firefly is not heated to incandescent temperatures.
4.  The experimental evidence of case 3 does not mean that case 2 does not emit visible light.

Note that one form of bioluminesence is "foxfire" in forest fungi.  I could claim that it was named in my honor, but it probably comes from the French "faux" for false.  An interesting coincidence is that the same phenomenon is named after foxes ("kitsunebi") in Japanese folklore.  See the Hiroshige print "New Year's Eve Foxfires at the Changing Tree, Oji, No. 118 from One Hundred Famous Views of Edo"  https://www.brooklynmuseum.org/opencollection/objects/121730
I tried to obtain a copy of this print, but had to settle for a museum-quality reproduction.

TimFox:
"A 2 page paper would do the job. Based on one little X involving the speed of electricity along a threaded rod compared to a plain rod. I would do it if i had access to a good scope."

In olden days, when impedances were higher (for use with vacuum tubes) and speeds were more leisurely, delay lines were made from coaxial cables where the solid center conductor was replaced by a tightly-wound helical coil.
As a transmission line, this increased the inductance per unit length substantially, with some increase in the capacitance due to dimensions.  This increased the characteristic impedance and the delay time per unit length, following the usual equations for coax cable.

Specifically, RG-65/U (still available in a later version) has:
     Polyethylene dielectric:  OD = 0.285 in
     Center conductor:  helix with ID = 0.11 in, 112 turns/in of AWG 32 (0.008 in diameter) wire.
     Core inside helix:  0.11 in diameter polyethylene.

Parameters:  Z0 = 950 ohms, velocity factor 29 time slower than solid polyethylene coax, delay time = 130 ns/m.

With such a slow, high-impedance construction, you shouldn't need a very expensive oscilloscope to compare it to a conventional coaxial cable.

Note that in 1965, more extreme cables were available that included a ferromagnetic core inside the helix (to increase the inductance) and lower-capacitance (thicker) dielectric.  Examples included:
(HH-1500A) 1500 ohms, 230 ns/m;  (RG-176/U) 2200 ohms, 9360 ns/m (?);  (DL1100) 1100 ohms, 1800 ns/m; (HH-4000) 3900 ohms, 3350 ns/m.

See:  J Millman and H Taub, Pulse, Digital, and Switching Waveforms, McGraw-Hill 1965.  Appendix B, pp 798 to 799.

aetherist:

--- Quote from: TimFox on April 13, 2022, 05:24:33 pm ---
--- Quote from: aetherist on April 13, 2022, 12:47:34 am ---
--- Quote from: TimFox on April 12, 2022, 09:20:53 pm ---Once again, you are wrong.  The diagnostic equipment and beam testing procedures that I suggested you read clearly show that the magnetic field outside a beam of charged particles is identical to that outside a wire.
In a particle accelerator, one can compare the current with these magnetic sensors to the current that hits a Faraday cup (which suppresses the effect of secondary emission from the target).
Have you ever seen a particle accelerator, or read anything about them?
What do your countrymen at the Australian Synchrotron Lab say?

PS:  doing some elementary Googling, I found an interesting engineering thesis from Georgia Tech back in 1962:  https://smartech.gatech.edu/bitstream/handle/1853/14924/lineberger_william_c_196212_ms_69818.pdf?sequence=3&isAllowed=y 
The author discusses practical methods for measuring the magnetic field induced by a beam of charged particles without interrupting the beam.  Since this was already a physical phenomenon applied to practice in engineering, no one needed to crow about it.
--- End quote ---
But, if the magnetic field of a steady DC electron beam in vacuo (in a glass tube) is equal to the magnetic field of the wire supplying the steady DC, then this falsifies the STR explanation (ie that it is due to the length contraction of the wire), because there is no wire for the electron beam, there is only vacuum.
The vacuum contains spacetime, & i suppose that Einsteinists could claim that the space of the spacetime contracts, but that would i think require that the electrons spacings also contract, which would give the beam a double dose of negative charge, which is the opposite of what Einsteinists are looking for.

--- End quote ---

Your logic here is fallacious.
1.  It is well-established experimentally that current through a wire and current in a beam of charged particles induce a magnetic field B, according to the law of Biot and Savart that is later incorporated into Maxwell's Equations.
2.  Purcell published an explanation for a particular common case of current flowing through a metallic conductor, where the substantial magnetic field is induced despite the wire being electrically neutral.  There is some controversy about his derivation, some of which suggests that it is only useful as a pedagogical explanation.  However, quantitatively, it agrees with experiment.  He did not discuss this as an explanation for other situations of current, although he does say elsewhere in his textbook that there are other forms of current besides that in a wire.
3.  The case of a charged particle beam is a different configuration, since the beam itself is not electrically neutral and the velocity can easily be "relativistic" or "very relativistic" for an electron beam at a reasonable kinetic energy, while the drift velocity in Purcell's explanation is not so large.
4.  The experimental evidence for case 3 does not refute case 2, since the basic situations are different but the current is the same.

I can make fun of your logic with this analogy:
1.  Visible light is that portion of the electromagnetic spectrum that can be sensed by human vision.
2.  A common source of visible light is an incandescent light bulb, where current through the filament heats it to incandescence and much of the electromagnetic radiation emitted by the hot filament is visible.
3.  Another source of visible light is bioluminesence, produced by chemical processes within a living organism.  There is no external source of electricity to the firefly, and the firefly is not heated to incandescent temperatures.
4.  The experimental evidence of case 3 does not mean that case 2 does not emit visible light.

Note that one form of bioluminesence is "foxfire" in forest fungi.  I could claim that it was named in my honor, but it probably comes from the French "faux" for false.  An interesting coincidence is that the same phenomenon is named after foxes ("kitsunebi") in Japanese folklore.  See the Hiroshige print "New Year's Eve Foxfires at the Changing Tree, Oji, No. 118 from One Hundred Famous Views of Edo"  https://www.brooklynmuseum.org/opencollection/objects/121730
I tried to obtain a copy of this print, but had to settle for a museum-quality reproduction.

--- End quote ---
I don’t see any reason to change one word of anything i have written on this thread.

Re Purcell's STR explanation. I will now add that in his final step (of his derivation of the equation) he invokes a relativistic change in the Coulomb force to correct the force to a value seen in the stationary lab frame. However, in STR, charge has the same value in every frame, ie Einsteinists say that charge is invariant. But Purcell says that the force (due to charge) is not invariant. Smells fishy to me.

Earlier i pointed out Purcell's mistake/push that he did in his first step, & it looks to me that he adds another in his final step. I think that the 2 pushes are in the same direction, ie they don’t negate each other. If they negated then he would not need them.

Anyhow, its amazing how any kind of such STR analysis can get anywhere near the correct number.

If an aetherist applied a (neoLorentz) relativistic length contraction to the wire (instead of the silly Einsteinian length contraction) then nothing much would result.  The wire suffers a length contraction (& width contraction)(& so duz the observer) due to the aetherwind passing throo the wire (& throo the observer). This physical real absolute contraction affects everything in & on the wire, which duznt much affect or explain any charge or voltage or amperage etc. The observer might need to correct her numbers depending on her velocity & the velocity of the wire, but this kind of correction due to change of frame could never be invoked to explain any phenomenon (that i can think of).

TimFox:
I didn't think you would change anything.
I just preach to the choir.

aetherist:

--- Quote from: TimFox on April 13, 2022, 08:40:29 pm ---"A 2 page paper would do the job. Based on one little X involving the speed of electricity along a threaded rod compared to a plain rod. I would do it if i had access to a good scope."

In olden days, when impedances were higher (for use with vacuum tubes) and speeds were more leisurely, delay lines were made from coaxial cables where the solid center conductor was replaced by a tightly-wound helical coil.
As a transmission line, this increased the inductance per unit length substantially, with some increase in the capacitance due to dimensions.  This increased the characteristic impedance and the delay time per unit length, following the usual equations for coax cable.

Specifically, RG-65/U (still available in a later version) has:
     Polyethylene dielectric:  OD = 0.285 in
     Center conductor:  helix with ID = 0.11 in, 112 turns/in of AWG 32 (0.008 in diameter) wire.
     Core inside helix:  0.11 in diameter polyethylene.

Parameters:  Z0 = 950 ohms, velocity factor 29 time slower than solid polyethylene coax, delay time = 130 ns/m.

With such a slow, high-impedance construction, you shouldn't need a very expensive oscilloscope to compare it to a conventional coaxial cable.

Note that in 1965, more extreme cables were available that included a ferromagnetic core inside the helix (to increase the inductance) and lower-capacitance (thicker) dielectric.  Examples included:
(HH-1500A) 1500 ohms, 230 ns/m;  (RG-176/U) 2200 ohms, 9360 ns/m (?);  (DL1100) 1100 ohms, 1800 ns/m; (HH-4000) 3900 ohms, 3350 ns/m.

See:  J Millman and H Taub, Pulse, Digital, and Switching Waveforms, McGraw-Hill 1965.  Appendix B, pp 798 to 799.

--- End quote ---
Interesting. Elektons hugging the AWG32 would need to propagate 39 helical ft per lineal ft of coax, which would take 39 ns/ft at c, or 60 ns/ft at 2c/3 in the insulation (if wires are coated), or 180 ns/yd, or 198 ns/m.
U mention 130 ns/m, which is much faster than my 198 ns/m. I would have expected it to be slower than my 198 ns/m.

But when i mention an X using threaded rod, my elektons hugging the surface would go up&down&up over the threads, elektons would not go the long way around&around.  Hence a helical kind of wire would not do the trick.

X1.  Elektons going along a 10 ft plain rod would take 10 ns to go to the end & 10 ns to reflect back to the start.
For a 10 ft threaded rod that 20 ns might double to 40 ns, koz of the extra distance up&down&up.
A 350 MHz scope can detect say  3 ns, hence it could detect the 20 ns diff tween 20 ns & 40 ns.

X2. If the rods were then painted, the times would increase to 30 ns & 60 ns, a diff of 30 ns.

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