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

[T3sl4co1l]

And for the record, I use KL just fine (or so it seems ) around transformers---as components.  Or transmission lines (same thing).  And by extension, antennas, RF amplifiers, etc.; again, as components (or more accurately, ports).

Very interested in your explanation of how this can be "so wrong", yet works far more often than chance?  Let alone how correct it is (or in what sense, correctness is meant).

(Even attempting a statistical argument is peculiar here, but arguably acceptable.  For example, consider the common advice, "place bypass caps at power pins".  This isn't always a good idea, but it turns out to be effective more often than not.  Such an example would be evaluated over the distribution of typical design approaches.  For example, whether the novice uses random e.g. autorouting, ground fill, inner planes, etc., and how well stitched the pours/planes are, if applicable.  Many examples turn up on this very forum, providing a representative sample from amateurs to rookie and seasoned engineers.)

Tim

[EEVblog]

But someone has to say this: your understanding of electricity is incomplete. Even for a "practicing" engineer.

There is a huge difference between lack of understanding and simply not caring about the physics details. I understand the argument, I just don't care.
I'm essentially on Medhi's side when it comes to the KVL debate, even though I have categorically stated that Lewin is not wrong.

[EEVblog]

Well, you thought they worked, your customers thought they worked, but now you know this was just all an illusion.

Guys, you're so melodramatic.

And you are trolling.

Once again, lest this thread repeat the Mehdi/Lewin KVL thread, there is basically no one here, myself included, that disagrees with the fundamental physicss.
Most are just happy to get on with their engineering life using KVL and KCL and be done with it.
If you want to argue the physics knock yourself out, just don't expect anyone else to indulge you, nor get upset when people just roll their eyes at you 

[bsfeechannel]

Perhaps you didn't comprehend.  I asked why the products designed by uninformed cretins seem to work OK despite your alleged 'gross errors' in analysis.

"Uninformed cretins" can design things using solutions devised by those with the appropriate knowledge. If someone gives you the equations you need to design a transformer, you can do that without knowing Faraday's law. However you would not know exactly why that equation works, whether that is an approximation, or what assumptions were taken, etc. You'd be limited.

When something odd or different from expected happens, you'll be lost.

Are you suggesting that in fact, the products do not function as intended?

No. That's a complete non-sequitur argument that you, T3sl4co1l and others invented because you have no other. What I said is that circuit analysis can't explain how energy flow in circuits, because the theory obviously has its limits.

OK, has anyone here proposed designing a transformer using Kirchoff's laws?  I think that thread is long enough and pretty dead by now, no need to drag it over here.

Someone brought KL up. I'm just going along for the ride.

[T3sl4co1l]

I suppose it figures that, once all the inquiring minds have long left this thread, their questions answered, all that's left are the trolls.

I should've left this thread pages ago.  Well, better late than never.

Tim

[EEVblog]

I suppose it figures that, once all the inquiring minds have long left this thread, their questions answered, all that's left are the trolls.

That being said, there is nothing wrong with being a "troll" on this topic and delving into the physics details. In fact I fully support and encourage it, it's what the forum is for, and I do personally find it rather interesting (until it just goes on ad-nauseam)
But when people start accussing others of not having the knowledge, not wanting to know, being embarrassed to be shown up or whatever the rhetoric is, it gets a bit much and it's no surprise when people stop participating.

[bdunham7]

"Uninformed cretins" can design things using solutions devised by those with the appropriate knowledge. If someone gives you the equations you need to design a transformer, you can do that without knowing Faraday's law. However you would not know exactly why that equation works, whether that is an approximation, or what assumptions were taken, etc. You'd be limited.

When something odd or different from expected happens, you'll be lost.

I'm starting to doubt you a bit.  That statement seems ridiculous on the face of it.  The implications of Faraday's law seem blindingly obvious when it comes to transformer design, provided you understand leakage inductance.  There are a slew of more complex factors that are actually likely to bite you if you miss them in a transformer design.  Not that I'm an expert in the field, but I think core magnetics--permeability, whether you want energy storage, hysteresis, etc etc would merit more concern than pondering Faraday.  And those are things you mostly look up, not derive from first principles.  Somebody who designs transformers is welcome to correct or further enlighten me.

[EEVblog]

"Uninformed cretins" can design things using solutions devised by those with the appropriate knowledge. If someone gives you the equations you need to design a transformer, you can do that without knowing Faraday's law. However you would not know exactly why that equation works, whether that is an approximation, or what assumptions were taken, etc. You'd be limited.

When something odd or different from expected happens, you'll be lost.

I'm starting to doubt you a bit.  That statement seems ridiculous on the face of it.  The implications of Faraday's law seem blindingly obvious when it comes to transformer design, provided you understand leakage inductance.  There are a slew of more complex factors that are actually likely to bite you if you miss them in a transformer design.  Not that I'm an expert in the field, but I think core magnetics--permeability, whether you want energy storage, hysteresis, etc etc would merit more concern than pondering Faraday.  And those are things you mostly look up, not derive from first principles.  Somebody who designs transformers is welcome to correct or further enlighten me.

As always, it depends how deep down the rabbit hole you want to go.
Just grabbed my copy of Engineering Electromagnetic by Hayt and literally the first page is this.
Can't remember ever picking up Hyat to do anything practical, it's Maxwell ridden theory text. Greatif that's what you are after, but you wouldn't pick it up to design a transformer.

[bsfeechannel]

There is a huge difference between lack of understanding and simply not caring about the physics details. I understand the argument, I just don't care.
I'm essentially on Medhi's side when it comes to the KVL debate, even though I have categorically stated that Lewin is not wrong.

Maybe I'm getting old and my brain is failing me, but you can't say Lewin is not wrong and be on Mehdi's side. Mehdi says Lewin is wrong. This is a contradiction.

If Mehdi had at least a debatable argument. But the debate ended long ago, already in the 19th century. His accusation of Lewin's bad probing is ridiculous, to say the least. I won't rekindle the discussion because we already have two long threads about the subject.

Mehdi says that this is how engineers think. No they don't. At least the engineers with whom I had the privilege of working with do not project their ignorance on somebody else, especially if that person's job is to open your eyes to the limits of your concepts.

Mehdi was not constituted a representative of any body of engineers anywhere. When he says things like that he's just talking out his ass. Lots of people don't like him, me included, because his attitude raises many ethical issues.

[EEVblog]

There is a huge difference between lack of understanding and simply not caring about the physics details. I understand the argument, I just don't care.
I'm essentially on Medhi's side when it comes to the KVL debate, even though I have categorically stated that Lewin is not wrong.

Maybe I'm getting old and my brain is failing me, but you can't say Lewin is not wrong and be on Mehdi's side. Mehdi says Lewin is wrong. This is a contradiction.

I have absolutely no interest in debating this with you. Just wanted to say that.

[EEVblog]

Mehdi was not constituted a representative of any body of engineers anywhere. When he says things like that he's just talking out his ass. Lots of people don't like him, me included, because his attitude raises many ethical issues.

Ever wondered that people may think the same of you?
At least he's not an anonymous person on a forum, and wants to debate stuff genuinely.
Good luck trying to find a sparring partner.

[MIS42N]

"Uninformed cretins" can design things using solutions devised by those with the appropriate knowledge. If someone gives you the equations you need to design a transformer, you can do that without knowing Faraday's law. However you would not know exactly why that equation works, whether that is an approximation, or what assumptions were taken, etc. You'd be limited.

When something odd or different from expected happens, you'll be lost.

I think I am somewhat in the "Uninformed cretin" category as I 'use solutions devised by those with the appropriate knowledge'. So far that approach hasn't let me down until this thread. In my Reply #648 I proposed a solution based on what I believe is a reasonable approach. I would appreciate someone looking at this and either verifying my assumptions or shooting them down.

It seems a simple question. A wire carrying current creates a flux. A proportion of that flux cuts a parallel wire. We could put figures on it to match AlphaPhoenix video: wires 1mm diameter, spacing 250mm. What's the proportion?

The trick to being an uninformed cretin is to know enough to ask the right question.

[bsfeechannel]

And you are trolling.

I am trolling, Lewin is trolling, Derek's trolling. None of us are really trying to open your eyes.

Once again, lest this thread repeat the Mehdi/Lewin KVL thread, there is basically no one here, myself included, that disagrees with the fundamental physics.
Most are just happy to get on with their engineering life using KVL and KCL and be done with it.

What Lewin said is mainstream electromagnetism: KVL/KCL have its limits. Duh.

What some people understood is that Lewin mandated that you can no longer use KVL and KCL for circuit analysis. Gimme a break.

Lewin then shows/proves/references in the literature that KVL and KCL are a special cases of Maxwell's equations. Duh.

Then someone denies that without any proof and gets pissed off when people shows they are in fact disagreeing with fundamental physics.  Come on!

If you want to argue the physics knock yourself out, just don't expect anyone else to indulge you, nor get upset when people just roll their eyes at you 

Without proper knowledge of physics we are nothing. What Lewin and others brought about has important implications for practical engineering.

Couldn't care less if people are indulging me or rolling their eyes at me. What I care is that this pride of ignorance has nothing to do with engineering. So what I do is to try to show people the way to their own enlightenment. Many have realized what is at stake and upgraded their understanding. And I learned a lot in the process. That's something to be proud of.

[bsfeechannel]

I have absolutely no interest in debating this with you. Just wanted to say that.

That's fine with me.

Mehdi was not constituted a representative of any body of engineers anywhere. When he says things like that he's just talking out his ass. Lots of people don't like him, me included, because his attitude raises many ethical issues.

Ever wondered that people may think the same of you?

Oh yes, I've been called--let me check--a clueless, totally idiotic, fulla BS, dishonest, ignorant, disingenuous, no-oscilloscope charlatan.

Do I care? No. This is the price you pay when you oppose dipsticks with a megaphone, which is what the Internet turned out to be.

At least he's not an anonymous person on a forum, and wants to debate stuff genuinely.

This is something I'd like to believe.

[bsfeechannel]

Greatif that's what you are after, but you wouldn't pick it up to design a transformer.

See below.

Somebody who designs transformers is welcome to correct or further enlighten me.

It's all there. From Maxwell to an actual transformer. Brought to you in glorious potato vision.




This is when I believed I could contribute meaningful knowledge to the community. Until you-know-who said that you could design everything with KVL because it, according to his misconception, "always holds". No wonder the father mocker never made a video about transformer design.

[bdunham7]

It's all there. From Maxwell to an actual transformer. Brought to you in glorious potato vision.
This is when I believed I could contribute meaningful knowledge to the community. Until you-know-who said that you could design everything with KVL because it, according to his misconception, "always holds". No wonder the father mocker never made a video about transformer design.

That's a pretty good introductory video for someone with little or no idea on transformer basics, or even a run-through for someone who is rusty.  But it isn't the sort of thing you'd reach for when you suddenly need to design a custom transformer for some specific purpose and you don't do it on a regular basis.  You'd look for a reference like this instead.  And I'm fairly sure that the experienced engineer that wrote this article knows every single thing you have in your video. 

https://talema.com/smps-transformer-design/

[EEVblog]

It's all there. From Maxwell to an actual transformer. Brought to you in glorious potato vision.

This is when I believed I could contribute meaningful knowledge to the community. Until you-know-who said that you could design everything with KVL because it, according to his misconception, "always holds". No wonder the father mocker never made a video about transformer design.

Who is the "father mocker"? Why the insults?
That's all basic engineering transformer theory, just jump to the transformer formulas and you are good to go for most cases. For specific useage cases, other formula exist. Little need for any advanced maths or physics. And I'm NOT saying it's not good to know where it all comes from. Go and read Hayt and see how deep the rabbit hole goes. But like I said, it's not a text you'd pick up to design your transformer.

[Sredni]

There is a huge difference between lack of understanding and simply not caring about the physics details.

In this case the detail are relevant. This thread is about Derek's thought experiment that has all to do with the details of what happens in the first handful of nanoseconds in the circuit. You are free to ignore the details, but then why do you insist in hammering that square peg into this round hole?

Newtons laws continue to hold for practically every daily use it's put to by every practicing engineer everywhere.
You can even uses them to compute probe trajectories to Pluto.
But if you want to understand how to correctly synchronize your probe and satellite timers, you need to go into the nitty gritty details of general relativity. There is no point in saying "I don't care about faffing around those edges of physics". Your circuits won't work.
The microcontroller timer you build here on Earth will still work fine, yes. So what? Does that mean you can avoid thinking about details for systems that require those details to be understood?

The same is true for Derek's experiment. It's all about the details in the first instants after the big switchon. You open a thread about it and then conclude that you do not care about what's really going on because "it's on the edge of physics" and you can get more or less the behavior right if you ignore the first nanoseconds???

So fascinating.

[EEVblog]

There is a huge difference between lack of understanding and simply not caring about the physics details.

In this case the detail are relevant. This thread is about Derek's thought experiment that has all to do with the details of what happens in the first handful of nanoseconds in the circuit. You are free to ignore the details, but then why do you insist in hammering that square peg into this round hole?

Newtons laws continue to hold for practically every daily use it's put to by every practicing engineer everywhere.
You can even uses them to compute probe trajectories to Pluto.
But if you want to understand how to correctly synchronize your probe and satellite timers, you need to go into the nitty gritty details of general relativity. There is no point in saying "I don't care about faffing around those edges of physics". Your circuits won't work.

You are blowing this way out of proportion and taking the statement too literally.

You open a thread about it and then conclude that you do not care about what's really going on because "it's on the edge of physics"

I did not open the thread.
I'm done here. It seems that there are people here who don't want to debate this honestly, they just want to berate people who are trying to help people look at it from other perspective.

[Sredni]

There is a huge difference between lack of understanding and simply not caring about the physics details.

In this case the detail are relevant. This thread is about Derek's thought experiment that has all to do with the details of what happens in the first handful of nanoseconds in the circuit. You are free to ignore the details, but then why do you insist in hammering that square peg into this round hole?

Newtons laws continue to hold for practically every daily use it's put to by every practicing engineer everywhere.
You can even uses them to compute probe trajectories to Pluto.
But if you want to understand how to correctly synchronize your probe and satellite timers, you need to go into the nitty gritty details of general relativity. There is no point in saying "I don't care about faffing around those edges of physics". Your circuits won't work.

You are blowing this way out of proportion and taking the statement too literally.

There is little room for proportions, here. Either you considered the details or not.

You open a thread about it and then conclude that you do not care about what's really going on because "it's on the edge of physics"

I did not open the thread.

You're right. You made two videos on the topic, and in the first one (where you made a lot of, what is the PC term? "inaccurate statements") you just linked this thread.

I'm done here. It seems that there are people here who don't want to debate this honestly, they just want to berate people who are trying to help people look at it from other perspective.

So, debating honestly means to say 'you are right' even when you are not?
You are right in saying that Poynting vector is pointing towards the battery at DC?
And that Feynman agrees with you on that?

Oh, well.

[EEVblog]

BTW, after talking with Derek at length on the video it was clear that there was no intentional troll toward engineers with the question. He genuinely thought the question would help his target audience of people who have learnt some basic electicical theory and weren't really taught how EM fields related to it later on.

With the testing he's doing now I pointed out the potential probing issues like with the AlphaPhoenix test, and how testing this is guaranteed to drag the engineers further into the debate.
And how any testing video is bound to be messy from an explanation point of view. And his videos always keep things to a simple level. If he has to start explaining scopes and probing, then he's probably lost half his audience. So there is a very good chance that he might not do a video at all after all the effort, we'll have the wait and see.

[Howardlong]

If he has to start explaining scopes and probing, then he's probably lost half his audience.

He lost me from his audience when the penny dropped about his trick question, not particularly about the dimensions of 1/c * s, but about the light turning on at any current level.

"How long would it take for the bulb to light up"

with the simplification

"The light bulb has to turn on immediately when current passes through it".

[Microdoser]

Well, this thread has gone down the pan and has almost zero connection to its original purpose.

Time to put it on ignore, so I don't constantly get pointless notifications.

[bdunham7]

In this case the detail are relevant. This thread is about Derek's thought experiment that has all to do with the details of what happens in the first handful of nanoseconds in the circuit. You are free to ignore the details, but then why do you insist in hammering that square peg into this round hole?

I think the original idea was to see what happens over a period of seconds (Derek) or microseconds (AlphaPhoenix) and how the fast the initial (nanoseconds) response was compared to the longer-term response of the full circuit.  I don't see any evidence that either of them intended to get bogged down in the minutiae of the exact picosecond-by-picosecond analysis of that initial EM-mediated behavior.  The story was simply that there was 'some' response in a time of about d/c.

Some people have proposed some (necessarily) simplified models including the transmission line.  In fact, the physical experiments seem to me to indicate that this is a pretty good starting point.  So are you here simply to yank Dave's chain about every grievance and supposed 'errors' that you have sniffed out or do you have something worthwhile to add?  Are you here to beat up on poor Kirchoff some more (what did that guy ever do to you?) or can you perhaps expand on, defend--and quantify--your assertion that current can flow in the load but not be observable to an oscilloscope connected across the terminals of that load?

 I was actually interested in the subject, including what you may have to say--not a pissing contest.

[Sredni]

In this case the detail are relevant. This thread is about Derek's thought experiment that has all to do with the details of what happens in the first handful of nanoseconds in the circuit. You are free to ignore the details, but then why do you insist in hammering that square peg into this round hole?

I think the original idea was to see what happens over a period of seconds (Derek) or microseconds (AlphaPhoenix) and how the fast the initial (nanoseconds) response was compared to the longer-term response of the full circuit.  I don't see any evidence that either of them intended to get bogged down in the minutiae of the exact picosecond-by-picosecond analysis of that initial EM-mediated behavior.  The story was simply that there was 'some' response in a time of about d/c.

Yeah, that's the whole point of Derek talking about energy to be transferred via the fields and not by the motion of the charges inside the conductor. Some energy gets to the load after d/c seconds (where d is the width of the circuit) and waaaaay before 2L/c seconds (where L is the half-length of the circuit) exactly because energy is carried by the fields.
And I'm not advocating picosecond by picosecond analysis, but what is debated here happens right after d/c when the fields hit the load.

Some people have proposed some (necessarily) simplified models including the transmission line.  In fact, the physical experiments seem to me to indicate that this is a pretty good starting point.  So are you here simply to yank Dave's chain about every grievance and supposed 'errors' that you have sniffed out or do you have something worthwhile to add? 

Well, I linked Ben Watson's simulation. So far the best youtube video made by someone who knows what is talking about on the matter.
I also tried to explain why the dual transmission line model cannot let you see correctly what happens in the first nanoseconds because it's literally zero dimensional in the transverse direction.
Look at Ben's simulation: do the two legs behave like ordinary transmission lines? Shouldn't you be seeing a symmetric red-.green aura going back and forth along the top and bottom conductors? While in this circuit the red-green aura travel along the bottom conductors first (whith a faint ghost on the top one) and then gets back on the top one? In my eyes this is a radically different behavior that tells me that field simulation is the way to go.

Are you here to beat up on poor Kirchoff some more (what did that guy ever do to you?) or can you perhaps expand on, defend--and quantify--your assertion that current can flow in the load but not be observable to an oscilloscope connected across the terminals of that load?

Kirchhoff is an absolute giant. I have the utmost respect for him, Weber, Neumann. But one must know the limits of applications of the tools he gave us. If current begins and ends before the probe tips are placed, or if the transient is too short lived to propagate to the internal resistance of the scope without being distorted and potentially cancelled by other fields coming from other parts of the circuit, there is no guarantee you can see what happens inside the resistor.
Circuit theory is a beautiful fairy tale where Prince Charming always saves the damsel in distress. I mean, where currents and voltages behaves in an ideal way. In the real world the damsel can leave the tower on a motorbike with the Black Knight.

Imagine Ben Watson's simulation with the complexities of an oscilloscope rig complete with probes attached to the load side. I don't know if the current in the scope internal resistance will replicate, even at a later time and rescaled, what happens inside the load resistance. I would need to run the simulation for such a short lived event.

Of course, you can model it with zero-dimensional transmission lines and get the same exact behavior instantaneously, if you like.
But is that what we  some  ok, at this point I guess I'm the only one interested in what actually happens.