General > General Technical Chat

"Veritasium" (YT) - "The Big Misconception About Electricity" ?

<< < (210/396) > >>

aetherist:
Howardlong messaged me the following info.
Rise time 10-90% at the scope is 36 ps. By the time it gets to the feedpoint, it'll be about 45 ps due to dispersion in the coaxial feed.
Fall time looks similar visually but I didn't take a measurement. Pulse width is 608 ps.

Howardlong has already mentioned that his signal crosses (first reaches) to the opposite wire in  80 ps which he says accords with the speed of light for the  24 mm distance tween the pair of wires in his  450 Ohm antenna ladder line. Howardlong in effect says that this supports Veritasium's expectation that Veritasium's bulb can possibly light (start to light) in 1/c seconds (ie 3.3 ns for Veritasium's 1000 mm spacing).

These kinds of transients have at least say 4 stages.
I wanted to have a closer look at Howardlong's experiments to look at the first stage, stage-1 of his transient. But i will come back to that another day.
Today i will jump ahead & look at stage-2 of his transient.

Howardlong X using 4 ft of ladder antenna line (wires 24 mm apart). He got 12 mV, with 58 mV in the other wire, which is 20.7% (20 GHz scope).
Schantz X using 100 ft of 300 ohm twin lead antenna line (wires 7 mm apart). He got 60 mV, with 340 mV in the other wire, which is 17.6% (100 MHz scope).
AlphaPhoenix X using 1000ft of 24AWG  enameled copper wire (wires 250 mm apart). He got 0.2 V, which climbed to 1.7 V, which is 11.8%(100 MHz scope). Actually his source is 5.0 V, so 0.2 V is 4.0%.
Silicon Soup (youtube) does a Finite-Difference Time-Domain simulation (1000 mm), gets a 0.3 mA signal from a 1.47 mA current, which is 2.0% 20.4%, for a mini-version of the Veritasium circuit. I don’t know how his pseudo-signal happens (its something to do with Maxwell)(displacement current perhaps).

All of the above percentages are astonishingly high. But i think i know what happens.

A step signal (voltage)(current)(Heaviside might say energy current)(Dollard might say impulse current)(whatever) propagates say to the right along the right half of our circuit, along the say bottom wire.
The bottom wire in that half is gradually flooded with negative charge, starting at the source (at the midpoint of the circuit), the flooding progressing to the right towards the short at the end.
The growing negative charge on the surface of the bottom wire gradually repels more & more free surface electrons (conduction electrons) on (along) the top wire, some go right (to the end), & some go left (to our bulb).
The electrons pushed right (along the top wire) tend to bunch up, because they are flowing in the same direction as the propagating step (in the bottom wire).
Actually, the free surface electrons in the top wire flow much more slowly (say c/100,000)(in the plastic insulation) than the step (2c/3)(in plastic), hence they are overtaken & left behind.
But, their wavefront propagates much faster (along the top wire) than c/100,000, perhaps c/100, perhaps c/10  (still thinking). Anyhow, the wavefront (along the top wire) too is overtaken.
The result is that say 50% of the escaping electrons in the top wire go left & 50% go right.
The electrons flowing left create a flow of electrons flowing left through our bulb, which manifests as a voltage drop across our bulb.
Our bulb turns on (weakly) a little after d/c seconds, ie as soon as (enough) electrons start to flow (leftwards) through the bulb on our top wire.
Our bulb glows brighter as the flow of electrons through the bulb increases.
After a short time the flow through our bulb reaches its initial maximum (say 10% of the current in the bottom wire).
[In the Veritasium gedanken (wire spacing d is 1000 mm) this would be a little after 1/c.]
Eventually the step (propagating right) in our circuit will get to the end of the bottom wire & will enter the top wire (via the short), & go to our bulb (while overtaking most of the electrons escaping to the left).
While the step is in the top wire it will push a much greater number of free surface electrons in the top wire towards our bulb, however this extra (temporary) current will lag the step (it might show as a hump on the scope).
When the main signal reaches our bulb the bulb will achieve full brightness, ie there will be a big sudden jump step in the voltage (followed by the aforementioned hump).
[In the Veritasium gedanken the main signal would reach his bulb in 1 second (his half circuit is 1 light second long).]

Regarding conduction electrons deep inside our top wire, these might drift left & right, in which case they would add to the current (at our bulb), but i reckon that any such drift would be insignificant.
However, conventional theory has it that this internal drift gives us 100% of what we call electricity.
I reckon that the induced drift in our top wire would add less than 1% to the initial current through our bulb.
Later, well after the main current first arrived, drift would account for nearnuff zero% of the current through our bulb.
And likewise surface electron flow would probably account for nearnuff zero%.

The electrons escaping to the left will give a current & voltage (signal) at the midpoint of our top wire (ie at our bulb). The size of the signal will depend on the wire spacing. The signal will begin to grow as soon as the E×H radiation reaches across, ie the delay is d (metres)/c (m/s), where d is the spacing, & c is the speed of light in the medium (usually air). More exactly, the delay will depend on the location of our switch, relative to our bulb.
[In the Veritasium gedanken this switch-to-bulb distance is approx the same as the spacing tween his wires anyhow.]

I doubt that a (simple conventional) LCRX lumped element transmission line model can predict transient current, using a simple LCRX paradigm, using simple speed of light.
Any such model needs smarter components.
And truer speeds (& truer flow of surface electrons).
However i have never had any hands-on experience with transmission lines, or TL models (or the application of electricity theory of any kind).
However the repulsion of the electrons from (along) our top wire is not unlike the action of lots of little capacitors tween the bottom wire & the top wire.

Perhaps someone could do a (simple conventional) transmission line model for Howardlong's experiment.

adx:
A lot of "advanced" thinking there, most of which I think I follow, but to me at least some is as confusing as the academic textbook treatments (with their diagrams of imaginary field lines, surface charges, and equations presented as some kind of reality in their own right).

I know it's only a work in progress and won't suggest it needs to fit this bill, but what I yearn for is some kind of description of rational physical reality which ultimately ties in well to experimental and numerical experience.


--- Quote from: aetherist on February 01, 2022, 09:48:22 pm ---... gets a 0.3 mA signal from a 1.47 mA current, which is 2.0%, ...

--- End quote ---
(original formatting)
20%?


--- Quote ---All of the above percentages are astonishingly high. But i think i know what happens.

--- End quote ---

To me and some others here, these results were astonishingly low. For a properly terminated transmission line (which the arms of this circuit can be) and differential drive (which is impossible for the arms because they are driven with a common mode voltage), the initial voltage and current should be 50% of the steady state.

I don't know what "free surface electrons" are, nor why they should flow at such extremely high speeds "in" the insulation (I assume you mean the interface between wire and plastic). c/1000000 is 300m/s, compared with a drift velocity of somewhere around say 0.00001m/s expected at ~~10mA in the wire. (That's about 10000000 times slower.) It doesn't sound like you mean a skin effect, where electrons go fastest in the outer portion of a wire.

One thing about a wavefront overtaking the 50% of electrons who go right, is that this wavefront travels at the speed of light, so not only does it overtake those electrons in this particular case, but there is nothing which can overtake it in any situation. In the simulations you can see the calculated spherical wavefront match the speed of the signal along the wires. The pushing force of the electrons is delayed by 1/c too, so by the time the force reaches the electrons in the top wire, the wavefront has already gone past that x position along the region of the bottom wire. The wavefront is one and the same thing as the pushing force. It's hard to think of it in those terms (that a force can propagate in such a visually defined way through 'nothing'), but if we accept that the speed of light is a thing, then no other result is possible - we are watching the fabric of time itself in action.

From this thread I have learned there is no more to electricity than this pushing force, and resultant movement of mobile charge carriers (in this case electron drift within the confines of wire). Pulling forces exist with positive charge carriers and also an absence of negative charges.

I don’t believe any of the humps and bumps in Howardlong's result are due to any sort of difference between electron movement and what is conventionally known (EM, capacitance, magnetism). To me it's mostly down to measurement (and generator) risetimes and non-idealities. For those features visible in the simulations, it's possible to probe the simulation for understanding.

I was wondering if this experiment (eg AlphaPhoenix's) had proved some effect which has remained undiscovered (or more likely unnoticed), but there is very little to suggest that there is anything other than something obvious and known going on.

Or rather it would be, if people generally understood how electricity works.

Someone working in the field (pun always intended) will gain a very good intuitive understanding of how electricity behaves, but can remain completely in the dark as to what it is. I think this is down to education of the subject being so physically abstract, to the point that the teachers themselves undoubtedly do not understand it. Concepts have not changed in 150-100 years, relying almost entirely on mathematical descriptions from some of the early greats in the field. I think their insights are sometimes forgotten next to their maths. Textbooks have formed a strong collection of opinions, trotting out the same received truths, but their focus is on how to best educate students, not to clarify the world's "description of rational physical reality" mentioned above. Somewhere along the way, the meaning has become lost.

SandyCox:
 :-DD The flat-earth version of Electrodynamics.

aetherist:

--- Quote from: adx on February 04, 2022, 02:08:14 pm ---A lot of "advanced" thinking there, most of which I think I follow, but to me at least some is as confusing as the academic textbook treatments (with their diagrams of imaginary field lines, surface charges, and equations presented as some kind of reality in their own right).
I know it's only a work in progress and won't suggest it needs to fit this bill, but what I yearn for is some kind of description of rational physical reality which ultimately ties in well to experimental and numerical experience.
--- Quote from: aetherist on February 01, 2022, 09:48:22 pm ---... gets a 0.3 mA signal from a 1.47 mA current, which is 2.0%, ...
--- End quote ---
(original formatting) 20%?
--- End quote ---
Yes 20.4% -- thanx – fixed.
But 20.4% for 1000 mm spacing is mindblowing.  I thought that the 2.0% should have been more like 0.2%.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---
--- Quote from: aetherist on February 01, 2022, 09:48:22 pm --- All of the above percentages are astonishingly high. But i think i know what happens.
--- End quote ---
To me and some others here, these results were astonishingly low. For a properly terminated transmission line (which the arms of this circuit can be) and differential drive (which is impossible for the arms because they are driven with a common mode voltage), the initial voltage and current should be 50% of the steady state.
--- End quote ---
I am surprised that conventional lumped element models for TLs have not yet been proven to umpteen decimals. What happened?   
I asked that someone do a TL model for Howardlong's X. Such a model would ideally predict/postdict each of the say 4 stages of the initial transients (of the induced currents)(before the main current arrives). And it could ideally predict/postdict the other say 10 stages of later transients (after the main current arrives)(transients caused by reflexions i suppose). However i suspect that such models were never designed to predict initial transients. I suspect that the models are okish for the later transients. Anyhow i am surprised that today there exist any problems with the application of TL models. Or, are they mainly for amusing skoolkids? ? ? ? ?
Look at all of the pseudo-mini-capacitors joining the top wire to the bottom wire (in TL models). They are drawn with a say 1 mm gap. For the Veritasium gedanken i reckon that they should have 1000 mm gaps. Look at the induced pseudo-current from the pseudo-mini-capacitors, i bet that it is all sent towards the pseudo-bulb, no, i reckon that a half should be sent away from the bulb.
--- Quote from: adx on February 04, 2022, 02:08:14 pm --- I don't know what "free surface electrons" are, nor why they should flow at such extremely high speeds "in" the insulation (I assume you mean the interface between wire and plastic). c/1000000 is 300m/s, compared with a drift velocity of somewhere around say 0.00001m/s expected at ~~10mA in the wire. (That's about 10000000 times slower.) It doesn't sound like you mean a skin effect, where electrons go fastest in the outer portion of a wire.
--- End quote ---
Free (surface) electrons are my idea. They are conduction electrons that live on the outside of a wire. On a bare wire they might flow at say c/10,000 in air, & a bit faster than c/10,000 in vacuum -- & say c/100,000 (ie 3 km/s) in the (air in the porous) plastic insulation (ie the portion of the plastic touching the copper), which is 30,000,000,000,000 times faster than pseudo-electron-drift inside copper.
My flow of free electrons is not a skin effect, skin effect is inside the copper.  I am happy with a concept of electron drift inside copper, & electron drift close to the surface (skin effect). But i don’t think that such drifts are significant, & i don’t like the conventional idea that electric current is due to average drift or somesuch (hence i said pseudo-electron-drift).
And i don’t like the conventional idea that slowly drifting electrons can bump each other & make a wave that propagates along a wire at nearly the speed of light. Especially as the speed of em radiation in copper is (i think) 10 m/s.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---One thing about a wavefront overtaking the 50% of electrons who go right, is that this wavefront travels at the speed of light, so not only does it overtake those electrons in this particular case, but there is nothing which can overtake it in any situation. In the simulations you can see the calculated spherical wavefront match the speed of the signal along the wires. The pushing force of the electrons is delayed by 1/c too, so by the time the force reaches the electrons in the top wire, the wavefront has already gone past that x position along the region of the bottom wire. The wavefront is one and the same thing as the pushing force. It's hard to think of it in those terms (that a force can propagate in such a visually defined way through 'nothing'), but if we accept that the speed of light is a thing, then no other result is possible - we are watching the fabric of time itself in action.
--- End quote ---
I believe that electricity (& everything else) is a process of & in the aether. I don’t believe in Einsteinian stuff. But i doubt that that is important here. I mentioned charge propagating along the bottom wire, but i didn’t explain. My idea is that electricity is mainly due to electons propagating along the surface of a wire. Electons are photons that hug the wire, propagating at the speed of light, eg the speed of light in plastic if the wire is coated. Electons have a negative charge, which might be equal to an electron's charge (or it might be more)(or less).
Anyhow, i can explain my electon theory some other day, & anybody can follow my reasoning re the bottom wire if they simply assume that i am talking about charge propagating at the speed of light. Except that they would then of course be confused that my propagation along the bottom wire is at the speed of light c/1 whilst my flow of surface electrons along the top wire is at c/100,000. The difference in speed is because one is a kind of photon whilst the other is a kind of particle.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---From this thread I have learned there is no more to electricity than this pushing force, and resultant movement of mobile charge carriers (in this case electron drift within the confines of wire). Pulling forces exist with positive charge carriers and also an absence of negative charges.
--- End quote ---
My electon theory has pushing, but it does not have pulling.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---I don’t believe any of the humps and bumps in Howardlong's result are due to any sort of difference between electron movement and what is conventionally known (EM, capacitance, magnetism). To me it's mostly down to measurement (and generator) risetimes and non-idealities. For those features visible in the simulations, it's possible to probe the simulation for understanding.
--- End quote ---
I hope to analyse the (interesting) stage-1 of his initial transient later this week. Yesterday i looked into stage-2.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---I was wondering if this experiment (eg AlphaPhoenix's) had proved some effect which has remained undiscovered (or more likely unnoticed), but there is very little to suggest that there is anything other than something obvious and known going on. Or rather it would be, if people generally understood how electricity works.
--- End quote ---
Or, my new idea (that electricity in/on/along a wire is due only to two new causes), electons, & the flow of free (surface) electrons, might explain things better. We will see.
I had another look at AlphaPhoenix's youtube yesterday, & i noticed a few new interesting things which i will comment on in a day or two.
--- Quote from: adx on February 04, 2022, 02:08:14 pm ---Someone working in the field (pun always intended) will gain a very good intuitive understanding of how electricity behaves, but can remain completely in the dark as to what it is. I think this is down to education of the subject being so physically abstract, to the point that the teachers themselves undoubtedly do not understand it. Concepts have not changed in 150-100 years, relying almost entirely on mathematical descriptions from some of the early greats in the field. I think their insights are sometimes forgotten next to their maths. Textbooks have formed a strong collection of opinions, trotting out the same received truths, but their focus is on how to best educate students, not to clarify the world's "description of rational physical reality" mentioned above. Somewhere along the way, the meaning has become lost.
--- End quote ---
What do textbooks say about the speed of electricity being affected by plastic insulation?
What do the TL lumped element models say about it?
Notice that my electon theory has no such problem.

aetherist:
AlphaPhoenix   I bought 1000 meters of wire to settle a physics debate.
1,334,747 views     Dec 17, 2021           6,827 comments.
I constructed the Veritasium electricity thought experiment in real life to test the result.
If you were watching my community posts a month ago, the day that Derek over on Veritasium posted his video about electricity misconceptions, you saw me obsess over that problem a bit too much and immediately use it as the excuse I've been looking for for years to own my own oscilloscope. Instead of two light-seconds of wire, I used about 3 light-microseconds of wire, but it was PLENTY to resolve exactly what is happening in this circuit. I hope you enjoy the analysis!
Thanks to Derek at Veritasium for his blessing to make a real-world version of his gedanken experiment. If you haven't seen his video yet, you might want to go watch that for context, and I also highly recommend ElectroBOOM's video on the topic and EEVBlog's video on the topic. Electroboom's video has some simulated scope traces extremely close to what I saw IRL, and a REALLY fantastic animation (8:27) of him waving an electron around in his hand, shedding magnetic fields as it moves (Even though I ignore magnetic fields in this video - I'm trying to think of a test to find out if they matter).
Veritasium https://youtu.be/bHIhgxav9LY
ElectroBOOM https://youtu.be/iph500cPK28
EEVBlog https://youtu.be/VQsoG45Y_00

Pinned by AlphaPhoenix  1 month ago (edited) COMMENTS AND CORRECTIONS:
Thanks to Derek at Veritasium for his blessing to make a real-world version of his gedanken experiment. If you haven't seen his video yet, you might want to go watch that for context, and I also highly recommend ElectroBOOM's video on the topic and EEVBlog's video on the topic. Electroboom's video has some simulated scope traces extremely close to what I saw IRL, and a REALLY fantastic animation (8:27) of him waving an electron around in his hand, shedding magnetic fields as it moves (Even though I ignore magnetic fields in this video - I'm trying to think of a test to find out if they matter).
CORRECTIONS TO THIS VIDEO:
The most important thing I believe I ignored in this video is the actual, physical distribution of charge in the switch-side wire while the current is starting up. How much charge travels AT the advancing wavefront and how much charge gets stuck along the wire in between the fuzzball I drew and the battery will depend on the physical size of the wires and how close they are to each other, setting their capacitance.
This charge distribution also DOES NOT look the same on both sides of the switch, although I drew it that way for simplicity.
In a later experiment (next video) my mind melted a bit as I measured the resistors on both sides of the battery and found the current going through them is different.
It doesn't change any of the logic I presented in this video, but it makes some diagrams less than perfect.
It's possible that cross-inductance between the wires contributes to the effect, using almost exactly the same diagram except the wires are connected by a magnetic field rather than an electric field. I couldn't figure out how to decouple these effects day-of, so I'm still thinking on how to test. Hopefully more to come there.
I'm sure there will be loads more - please leave comments about what I screwed up.

AlphaPhoenix   I bought 1000 meters of wire to settle a physics debate.

Veritasium reckoned that the Poynting Field would light up his bulb soon after 3.3 ns, & that it would shine brightly ever after (& 1 second later a bit brighter when the main current arrives). 
AlphaPhoenix (Brian) mentions the Poynting Field at 11:40, but i think that Brian duznt care much for Veritasium's Poynting explanation for electricity. Brian merely said that his 1000 m X confirmed that Veritasium was correct that the bulb would turn on (& stay on) well before the main current arrived.
And Brian conceded that his 1000 m X could not verify Veritasium's 3.3 ns delay. Brian's switch he says takes over 20 ns to work (whatever that means). Brian is using a mickey mouse oscilloscope, ie only 100 MHz, which can't see finer than 10 ns.  He needs at least 1000 MHz, about $4,000. He can buy a used 20,000 MHz for $4,000, this can see 1/20th of a nanosecond.

Anyhow, Brian invented his own (unique i think) explanation for his early 0.2 V of current (which later climbed to 1.7 V). At 13:40 Brian says that when he flips his switch….
(1) His battery starts pumping electrons from one side to the other, & (2i) the negative wire gets a negative charge, & (2ii) the positive wire gets a positive charge, & (3) it creates a wave front of electrons pushing electrons along the negative wire, & (4) the pushing is modulated by photons of the em field which (5) travel at the speed of light, & (6) the pushing wave travels along the wire at approx the speed of light, which (7) creates a pocket of concentrated negative charge at the wavefront (going left), & likewise (8 ) we have a pocket of concentrated positive charge in the positive wire going right, & (9) electrons in the top (battery) wire interact with electrons in his bottom (bulb) wire, & (9) electrons sitting on the bottom wire near the bulb are free to move, & (10) they are pushed (repelled) & pulled (attracted) & pass through the bulb, giving (11) (not a lot of) current, but (12) it is almost immediate, (13) via the charge imbalance reaching across the air gap with electric fields, (14) without the far ends knowing. (15) Brian mentions two possibilities for the initial current at the bulb, (15i) capacitance tween the wires, & (15ii) inductance, & he says he will ignore inductance today, & he gives the above explanation for the capacitance effect. (16) Brian does not mention the Poynting Field or the Poynting Vector in his explanation.

My comments are as follows (here i am trying to explain Brian's ideas together with conventional ideas)(compared with my ideas)….

(1a) No. He does not have a battery, he has a 5 V DC source off his AC supply.
(1b) No. The 5 V does not start pumping when the switch is flipped, it is pumping all the time. Hence the negative wire already has a negative charge (across to the switch) before the switch is flipped, & the positive wire already has a positive charge (around to the switch).
(1c) If the end wires have been cut then the positive wire/charge must end at the cut. Which makes me wonder what the white trace would look like if that end was not cut & if only the left end was cut (i think the trace would look weird), & what would be Brian's explanation for the weird trace result (i think that he would have trouble trying to make his theory fit).
(1b again) The positively charged wire has a concentration of positive charge at the switch (the switch is a capacitor). And a concentration of positive charge near the bulb, in the length opposite the negatively charged wire (the wires are a capacitor).
(1d) Ok, now we flip the switch. Electrons already pushing on the switch now flow through the switch away from the -2.5 V terminal. After a short time this exit of electrons is felt back at the terminal, & electrons then start leaving the terminal, to replace the electrons going to & through the switch. A short time later this exit of electrons from the negative terminal is felt at the +2.5 V positive terminal, & electrons start entering the positive terminal from the positive wire. The 5 V source can't (initially) pump electrons at full flow because the positive wire is (initially) depleted (& to some extent the negative wire is initially over saturated). This shortage of electrons at the positive terminal will not be fully remedied until electrons have managed to flow from the switch around through the bulb & around to the positive terminal (ie 1 full lap of the circuit).
(1d) Indeed the green trace showing the voltage loss across the resistor near the positive terminal starts at zero volts & then slowly climbs gradually (in a lumpy way), & then does not reach its max voltage until a time corresponding to 1.2 full laps of the circuit. Brian says nothing about the green trace. His silly pumping idea should show the green trace starting at full current -- or more logically starting above full current, & slowly dropping to the steady full current as the distribution of charge along the wires reaches steady state, including the usual ups & downs due to any circuit related reflexions.

(4a) No. I reckon that an em field is not made of photons (not important today).

(5a) No. The em field does not travel at the speed of light. Or, yes, it does travel at the speed of light, but, the speed of light (& we assume the speed of em radiation) propagates at i think 10 m/s in copper (whereas i am sure that Brian assumes 300,000,000 m/s).

(6a) No. In view of (5a) above, how can the wave travel at almost the speed of light, or, yes, it might travel at the speed of light, but, the speed of light in copper is i think 10 m/s (whereas i am sure that Brian assumes 300,000,000 m/s).

(7a) No. In the light of (1abcd), Brian's pocket of concentrated negative charge starts at the switch not at the terminal. And, initially it is matched by a pocket of depleted negative charge starting at the switch & going to the terminal. And after it reaches the terminal there will be a new (small) burst of concentrated negative charge going away from the terminal. But, because the switch is close to the terminal, this complication is i suppose trivial.
(7b) No. Brian's concept of a pocket of charge at the wavefront is not realistic. The wavefront gives a leading edge, but the negative charge extends all of the way back to the terminal.
(7c) No. Brian thinks that he needs a pocket of negative charge well left of the bulb to repel electrons in the bottom wire to the right towards the bulb. A pocket of charge is not needed. Any kind of general distribution of negative charge in the top wire will repel electrons in the bottom wire, & common sense tells us that some of these will go right (for a while), no pocket needed.

(8a) No. We do not have a pocket of concentrated positive charge going right in the positive wire. Or, yes, we do, but, the green trace shows us that any such effect on the positive side of the circuit would be zero at first, & would take a long time to grow. But, the white trace does not show any evidence of that kind of growth. And, the pocket of positive charge is supposed to contribute say a half of the current through the bulb, ie a half of the white trace voltage, hence the white trace should definitely have growth (but duznt). Or, putting it another way, the green trace should not have growth (but it duz).
(7d) Similarly to (8a) if Brian showed us his trace for the resistor near the switch, i reckon that the current would have a quick spike & then fall, & after that grow in a similar fashion to the green trace.

(9a) Yes. Brian says that electrons sitting on the bottom wire near the bulb are free to move. Yes, it is the (conduction) electrons sitting on the surface of the wire (not in the wire) that are free to move. That is a key part of my own idea.

(10a) Yes & No. Yes, electrons are individually pushed (repelled) & pulled (attracted) & pass through the bulb. But, on the left half of the circuit, the overall charge in the top wire squeezes electrons out of the bottom wire, some going left (for a while), & some going right (through the bulb). And on the righthand half of the circuit the overall positive charge in the top wire attracts electrons in the bottom wire, & electrons near the bulb flow to the right (for a while), pulling other electrons through the bulb behind.

(11a) Yes. There will be some (not a lot of) current through the bulb, before the main current arrives.

(12a) Yes. The initial small current is almost immediate. However Brian's oscilloscope can't tell us exactly what happens in the first few nanoseconds, hence he can't actually answer the Veritasium gedanken question.

(15a) Brian mentions two possibilities for the initial current at the bulb, capacitance & induction. We could add radio as a separate class.
(15ia) Yes. Brian ignores inductance, because capacitance is the main culprit.
(15ib) No. Brian reckons that he explains the initial capacitance effect, but he duznt. His explanation has little resemblance to capacitance.

(16a) Yes. Brian quite correctly ignores Poynting in his explanation (unlike Veritasium who loves Poynting). Brian could have emphasized that Veritasium's Poynting explanation does not explain even one electron of what happens. Brian could have explained that Veritasium genuinely reckoned that there would be a very significant initial Poynting electric current. As it turns out there is indeed a significant initial current, but because of capacitance, not Poynting.
So, Brian's X pt1 did a good job, & we are all eager to see pt2. And me myself i want to see the trace for the resistor near the switch.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod