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Veritasium -- How Special Relativity Makes Magnets Work.
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TimFox:
By the way, a conventional passive current probe for an oscilloscope clamps around the wire.  If you send a pulse train down the wire, the probe should show the pulse shape, not its derivative, except that the DC level is not put out into the oscilloscope.  This is the same as a pulse transformer, which also rejects the DC level and has a limit at the high-frequency content, but responds to the pulse shape within its bandwidth limit.
A Tektronix P6022 passive current probe has a frequency response from 935 Hz to 120 MHz (at -3 dB).
aetherist:

--- Quote from: TimFox on April 21, 2022, 03:02:19 am ---By the way, a conventional passive current probe for an oscilloscope clamps around the wire.  If you send a pulse train down the wire, the probe should show the pulse shape, not its derivative, except that the DC level is not put out into the oscilloscope.  This is the same as a pulse transformer, which also rejects the DC level and has a limit at the high-frequency content, but responds to the pulse shape within its bandwidth limit.
A Tektronix P6022 passive current probe has a frequency response from 935 Hz to 120 MHz (at -3 dB).
--- End quote ---
Yes, i remember in those CERN papers that u linked they could get a fairly good looking (ie accurate) shape for their measurement of their pulses, at some (any) frequencys, due mainly to including some capacitance etc to create a pseudo-shape. Otherwise in theory they would just get a spike at the leading edge & a spike at the trailing edge. But i didnt try to understand it, ie even tho their explanation was much simplified for beginners.
aetherist:

--- Quote from: aetherist on April 19, 2022, 09:52:57 pm ---Yesterday i had a look at 5 or 6 youtubes by Christian Sutterlin on the channel called Jean de Climont.
Sutterlin says that magnetic fields are due to an electron's spin or spin precession or something, & that magnetic fields are not due to an electron's translation or motion (i don’t understand his theory)(i might have another look later).
Anyhow, i will make detailed comments on each of his youtubes later this week. Today i show links to 3 ovem below. He made 2 claims that especially caught my eye (i will comment on these later this week) …..
1. The magnetic field of an electron beam is cancelled when the beam deviates by 90 deg. He mentions an experiment using a 42mm glass tube with a 90deg bend, but this is confusing, i think that the laboratory never did complete that experiment, even tho Sutterlin mentions the experiment a number of times in a number of his youtubes.
2. When a current carrying long straight copper conductor is spun around its long axis the magnetic field increases by a factor of 5 for 100 rps or 10 for 260 rps. Here the magnetic field being measured is the standard field found around a stationary current carrying straight wire (it is not the axial field found in a coil)(he/they didn’t measure the axial field). He/they used a pulsed current (100 Hz i think), so that the detectors (2 coils) could get a reading.


Rowland with a rotating conductor.  [3:24 long]  171 views.   Jan 14, 2022  Jean de Climont (Anglais)  873 subscribers
Rowland's experiment shows a magnetic field. The electrons in the electrically charged, high-speed spinning disk form circles. They form a kind of loop and therefore create a magnetic field in the axis of the disc. The disc can be replaced by a rotating conductive cylinder and the static electrons by an electric current. The magnetic field of the rotating conductor is about five times greater than the field of an identical current of 1 Amperes at 100 Hz through the motionless conductor.
2 Comments. Mathew Orman  2 months ago. The same experiment with compass near moving Van De Graaff generator charged belt show no magnetic filed... Draw your own conclusion..
--- End quote ---
How could STR explain that spinning a Cu conductor at 260 Hz increases the magnetic field by a factor of 10?

The STR (length contraction) explanation assumes that velocity in the yy or zz plane has zero effect, it assumes that only the xx velocity has effect. Additionally, it assumes that it’s the average xx velocity that has effect (which i can shoot down very simply by explaining the math)(the average of the square roots of the 1-VV/cc for each drifting electron is not the same as the square root using the average V)(they use this average V)(which they of course know is wrong, ie not true to STR)(unless drifting electrons do indeed all drift at the same speed)(but they of course don’t mention this problem of averaging).

So, STR can't explain the factor of 10. So, what is the explanation? I don’t know. Still thinking.
TimFox:
Going back to the passive current probe:
The Tektronix P6022 example also has an adjustable compensation circuit to optimize pulse fidelity and frequency response.
The total electronic circuit is a transformer, with the input current (wire for the Tek, beam for the Bergoz) forming one "winding", and the coil (around a ferromagnetic core) forming the other winding.
One can couple a pulse through a transformer, losing the DC component and suffering some degradation of high-frequency performance, but a good circuit will not show merely two spikes from a pulse input.
In a current transformer driven by a pulsing current, if you see only a positive spike followed by a negative spike, that means that the load resistance is too high for the coil's inductance:  this is analogous to the bass response of an audio transformer being seen as a "droop" in the levels when driven by a square wave.
The self-inductance of the coil will short out the output voltage at DC, just as in a normal transformer.
The leakage inductance and parasitic capacitances will limit the high-frequency response, but can be compensated to some extent.
Note that both the scope probe and the beam probe can be adjusted and calibrated by running a known current through a wire down the bore, measuring the wire current after the probe in a normal way (into a resistor across a 'scope input, for example).
aetherist:

--- Quote from: aetherist on April 21, 2022, 03:27:30 am ---
--- Quote from: aetherist on April 19, 2022, 09:52:57 pm ---Yesterday i had a look at 5 or 6 youtubes by Christian Sutterlin on the channel called Jean de Climont.
Sutterlin says that magnetic fields are due to an electron's spin or spin precession or something, & that magnetic fields are not due to an electron's translation or motion (i don’t understand his theory)(i might have another look later).
Anyhow, i will make detailed comments on each of his youtubes later this week. Today i show links to 3 ovem below. He made 2 claims that especially caught my eye (i will comment on these later this week) …..
1. The magnetic field of an electron beam is cancelled when the beam deviates by 90 deg. He mentions an experiment using a 42mm glass tube with a 90deg bend, but this is confusing, i think that the laboratory never did complete that experiment, even tho Sutterlin mentions the experiment a number of times in a number of his youtubes.
2. When a current carrying long straight copper conductor is spun around its long axis the magnetic field increases by a factor of 5 for 100 rps or 10 for 260 rps. Here the magnetic field being measured is the standard field found around a stationary current carrying straight wire (it is not the axial field found in a coil)(he/they didn’t measure the axial field). He/they used a pulsed current (100 Hz i think), so that the detectors (2 coils) could get a reading.


Rowland with a rotating conductor.  [3:24 long]  171 views.   Jan 14, 2022  Jean de Climont (Anglais)  873 subscribers
Rowland's experiment shows a magnetic field. The electrons in the electrically charged, high-speed spinning disk form circles. They form a kind of loop and therefore create a magnetic field in the axis of the disc. The disc can be replaced by a rotating conductive cylinder and the static electrons by an electric current. The magnetic field of the rotating conductor is about five times greater than the field of an identical current of 1 Amperes at 100 Hz through the motionless conductor.
2 Comments. Mathew Orman  2 months ago. The same experiment with compass near moving Van De Graaff generator charged belt show no magnetic filed... Draw your own conclusion..
--- End quote ---
How could STR explain that spinning a Cu conductor at 260 Hz increases the magnetic field by a factor of 10?

The STR (length contraction) explanation assumes that velocity in the yy or zz plane has zero effect, it assumes that only the xx velocity has effect. Additionally, it assumes that it’s the average xx velocity that has effect (which i can shoot down very simply by explaining the math)(the average of the square roots of the 1-VV/cc for each drifting electron is not the same as the square root using the average V)(they use this average V)(which they of course know is wrong, ie not true to STR)(unless drifting electrons do indeed all drift at the same speed)(but they of course don’t mention this problem of averaging).

So, STR can't explain the factor of 10. So, what is the explanation? I don’t know. Still thinking.
--- End quote ---
Ok i think i know how 260 rps gives 10 times the magnetic field.
The non-spinning Cu tube has say 2.5 Amps, AC, at 100 Hz. The voltage goes from say plus V to minus V 100 times per second, minus V to plus V 100 times per second. That gives 200 spikes of 2V, per second.
When spinning at 260 rps the 2.5 Amps drops to 1.5 Amps due to the vibration & loss of contact of the carbon contacts.
The loss of contact i reckon results in say 9 additional spikes of V to 0V to V during one half of the cycle, & say 9 additional spikes of minus V to 0V to minus V during the other half.
Each extra spike is a negative spike, ie the new spike is a loss of current, not an injection of extra current, hence the loss of 1 Amp.
Thusly there are 2000 spikes of 2V, compared to 200 spikes for the non-spinning case. Hence 10 times the magnetic field. Interestingly there appears to be an extra 9 spikes per cycle at low rps & at the full 260 rps. I would expect less spikes at less rps. Hmmmm, praps the Cu tube at the contacts has 9 high points along its circumference, 5 at the carbon contact at one end, 4 at the other.
However, i now see that Norbert Feurle beat me to it.

Comment: Norbert Feurle  2 months ago…..
If the increase of the magnetic field is not caused by the spices generated in the carbon brushes, which would increase with rotating speed probably, then this is probably a closer aproximation of the electron: https://youtu.be/NoH9rn8p1w8

Comment: Mathew Orman  2 months ago……
The same experiment with compass near moving Van De Graaff generator charged belt show no magnetic filed... Draw your own conclusion.

Most of this info comes from  4:59 to 7:51 on the long youtube below.

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