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

[SiliconWizard]

QM, QED and QFT are non-intuitive and hard to grasp, but they certainly aren't a cute theory that fails.

I was specifically talking about the cases in which it "failed" so far. Do not generalize what I said, which would tend towards a strawman argument. =)

The fact that some of those QM results are difficult to observe directly doesn't invalidate or marginalize the theory in any way.

If a theory does not survive observations, then it is, as long as it's the case, a cute theory. We have absolutely experimented and observed its applicability in various contexts. But in others, it remains unobservable (not sure this is a word?), so for those cases, it remains a cute theory. This doesn't marginalize it. It just means we fail to prove it's valid in some contexts. Whether it's worth considering it for those contexts even though it's impossible to observe is up to everyone's appreciation. It's like the string theory. In science, it's sometimes hard to know when you're wasting your time or when stubbornness will pay off, and it's always tempting to think we have just found the theory of "everything".

And now yes, as I also said, there are seemingly some recent advances - experiments with large molecules - which I agree sound promising, but again I would be prudent at this point. Time will tell though.

[bdunham7]

I was specifically talking about the cases in which it "failed" so far. Do not generalize what I said, which would tend towards a strawman argument. =)

I don't intentionally do the strawman and although reductio ad absurdum often looks like that, I haven't intentionally done that here either. Perhaps there is a misunderstanding somewhere, so can you cite an example where standard QM/QED has 'failed'?  Or a situation or 'context' where it is not valid?

[rfeecs]

Perhaps you could read my post that I've linked and the one after it and then see whether you agree, disagree or don't understand my position on that.  Can you have a static E-field without charges?

I agree that moving the charge with tongs is creating an "energy flux".  It can be thought of as P = VI.  You will also create a magnetic field by moving that charge, so the Poynting theorem will give you the same answer.  It has to.  It is just math.  I am content to consider it a mathematical result with no practical value for the DC case.

I agree that a static E-field requires charges to create the field.  Let's say the E-field is created by separating charges and holding them in position.  That required energy.  You are saying the energy is in the charges instead of the field, or a combination of charge and field?

I agree that anything that changes that energy will require the movement of charges.

And yet, there is such a thing as "energy per unit volume"  of an electrostatic field:
https://en.wikipedia.org/wiki/Electric_potential_energy#Energy_stored_in_an_electrostatic_field_distribution

[bdunham7]

Perhaps you could read my post that I've linked and the one after it and then see whether you agree, disagree or don't understand my position on that.  Can you have a static E-field without charges?

I agree that moving the charge with tongs is creating an "energy flux".  It can be thought of as P = VI.  You will also create a magnetic field by moving that charge, so the Poynting theorem will give you the same answer.  It has to.  It is just math.  I am content to consider it a mathematical result with no practical value for the DC case.

I agree that a static E-field requires charges to create the field.  Let's say the E-field is created by separating charges and holding them in position.  That required energy.  You are saying the energy is in the charges instead of the field, or a combination of charge and field?

I agree that anything that changes that energy will require the movement of charges.

And yet, there is such a thing as "energy per unit volume"  of an electrostatic field:
https://en.wikipedia.org/wiki/Electric_potential_energy#Energy_stored_in_an_electrostatic_field_distribution

OK, it looks like we agree, 4 for 4.   

IMO, the energy of a static field has to be considered as a the combined effect of charges and their fields.  The energy per unit volume is an understandable and probably useful result of integral calculus, just like a lot of laws and observations (Faraday's Law, for example).  But for the DC case, the relevant point is that the energy of the static field is invariant.  Well almost, since waving electrons around with tongs will change the field a bit.

[bsfeechannel]

I have not heard a compelling case of Poynting at DC that makes me think in any way that it's useful.

Take your pick:

Nope, still not telling me anything useful, just stating that's a way to look at it.
What can looking at it that way DO FOR ME?

In the picture below, a DC is going through a solenoid. The magnetic field so generated is attracting a magnet that is moving at a constant speed due to friction. Clearly energy is coming from the solenoid and going to the magnet, which is being dissipated as heat.



But how do you explain that? Spooky action at a distance?

Could we have DC motors if energy weren't flowing already through the fields instead of the wires?

[bdunham7]

Clearly energy is coming from the solenoid and going to the magnet, which is being dissipated as heat.

Is it clear?  How about if we replace the coil with a big fixed permanent magnet?  Is energy flowing from the big magnet to the small one? 

[bsfeechannel]

Clearly energy is coming from the solenoid and going to the magnet, which is being dissipated as heat.

Is it clear?  How about if we replace the coil with a big fixed permanent magnet?  Is energy flowing from the big magnet to the small one? 

Ooh! I forgot to include the doggone switch.

[SiliconWizard]

I was specifically talking about the cases in which it "failed" so far. Do not generalize what I said, which would tend towards a strawman argument. =)

I don't intentionally do the strawman and although reductio ad absurdum often looks like that, I haven't intentionally done that here either. Perhaps there is a misunderstanding somewhere, so can you cite an example where standard QM/QED has 'failed'?  Or a situation or 'context' where it is not valid?

It's only been observed for very small particles (notwithstanding the mentioned recent experiments, which are interesting, but for which I'm still prudent.) And as I said earlier, any theory that can't survive observation under certain conditions can't be claimed to be valid for those conditions. So, while many physicists believe that the same laws hold at any scale, the honest ones will tell you that they just don't know. That it appears plausible, but we have no proof. The others are believers.

[SiliconWizard]

Clearly energy is coming from the solenoid and going to the magnet, which is being dissipated as heat.

Is it clear?  How about if we replace the coil with a big fixed permanent magnet?  Is energy flowing from the big magnet to the small one? 

Ooh! I forgot to include the doggone switch.

Well... yeah.
Because... in the two permanent magnets example, maybe the part that was neglected here was the initial energy required to place, and then hold the two magnets next to one another before any of them will move?

[SilverSolder]

Clearly energy is coming from the solenoid and going to the magnet, which is being dissipated as heat.

Is it clear?  How about if we replace the coil with a big fixed permanent magnet?  Is energy flowing from the big magnet to the small one? 

Arguably, you are storing potential energy while moving the magnets closer?  - and when they are standing still...  that energy is still there!

[bdunham7]

It's only been observed for very small particles (notwithstanding the mentioned recent experiments, which are interesting, but for which I'm still prudent.) And as I said earlier, any theory that can't survive observation under certain conditions can't be claimed to be valid for those conditions. So, while many physicists believe that the same laws hold at any scale, the honest ones will tell you that they just don't know. That it appears plausible, but we have no proof. The others are believers.

OK, I see our point of departure is at the definition of 'failure' of a theory.  So you are saying that if the theory is not feasibly falsifiable, we should remain skeptical.  It is not currently possible to experimentally verify the de Broglie wavelength of a tuna swimming in the sea, so your position is that we should regard any theoretical statement of it as unproven.  That's not an inherently unreasonable position, but keep in mind that it then also applies to common laws that we accept will apply universally, or at least over a broad set of conditions that we don't expect to be able to analyze experimentally.  I don't see QM/QED as being any different than any other physical laws or models in that regard.  It is verifiable until you simply reach experimental limits.  It's not like string theory, which AFAIK has not made any experimentally falsifiable conclusions.

[bdunham7]

Arguably, you are storing potential energy while moving the magnets closer?  - and when they are standing still...  that energy is still there!

If the magnets are aligned so as to attract, it takes negative energy to move them into position from any further position or as physics teachers would posit, from infinity.

[Sredni]

I am not talking about the measurements, they will be as they always have been. I'm talking about the the title of this thread "The Big Misconception About Electricity". Does the energy flow in the field around the wire or does it flow in the wire at DC? Poynting/classical field theory says outside, QFT appears to say inside.
I want to know what you and others who have been so (not incorrectly) dogged about anyone that dares think of this in any other way than Maxwell/Poynting think about this apparent conundrum.

What I'm saying is that I am not at all sure that the QFT theory pointo of view is at odds with what is forecasted by Poynting. It might make it harder to see, but if you get the same measurements for the fields, then chances are that energy flow will follow what Poynting forecasts.

Regarding that video on QFT, it seems to me the point made is that the conductors are best at 'communicating' the electric field. And I can see that in classical theory as well: if there is only the battery, the electric field of each pole dies off as 1/r^2, and whatever field was there near the poles of your 12V battery, will be greatly attenuated at the distance of 1 meter. But if you attach cables at the two poles and place the other ends near each other (let's say the same distance as the battery's electrodes) one meter away from the battery, you will basically see there the same field you see between the electrodes.
Now, if QFT explains this through probabilities of interactions, instead of fields propagating from charges, well, good for QFT. But does this tell us where the energy actually flows in the first few nanoseconds in Derek's experiment?
In a post above the author of the video says

"For the phenomena under discussion here Quantum Electro Dynamics would find that the path of highest probability is along the wire, where all the free electrons are and can interact with each other at inter atomic distances VS the vast 1m void between them and the bulb."

Well, but does this prevent the electric field from the battery from being measured at 1 meter from the electrodes before the interaction between electrons in the wires have made its round trip to the moon and back? I don't think so. You just see a far weaker field than what is allowed by the wires. And this is also what is expected by classical ED. After all, there is a reason why we use cables to power our homes and not big tesla coils...
It's far more efficient to influence the surface charge responsible for the internal electric field in the load by using the interaction between adjacent electrons in the wire, that it is by changing their configuration at a distance. Of course when the wires makes a longer trip than line of sight, we will have to wait a bit more for that far more efficient interaction to reach our load.

Regarding your other point about switching theories

"You don't need to go as far as Poynting to muddy the waters. Even plain Poynting Thereom can make things so complicated that you won't be able to have intuitive insights."
You are now saying the same thing that many people say about Poynting/Maxwell for DC and LF.

I can hardly see a parallel, here. Applying Poynting's theorem does not even represent a shift in paradigm. It's 'just' a cross product away from what you must already know in classical theory: i.e. what are the electric and magnetic field in your system. If would not consider it to be so complicated that it will prevent you from having intuitive insight. In my mind it's quite the opposite: it gives you insight on how the energy flows. But of course, YMMV.

Going quantum, on the other hand, changes everything. Current as movement of charge? Nah, there's no such thing as classical trajectory. You might want to consider probability amplitude wave packets in a periodic potential (free electrons? quasi-free? tightly bound? Pick your poison). Try to gain some insight by considering the momentum redistribution in the k-w space. If you're lucky you can try to picture a Fermi sphere in your head and what an electric field would do to that. Joule heating by collisions with the lattice? Forget about that! It's electron-phonon scattering and it's all about imperfections and impurities and the probability of transitions. And don't even think of turning on a magnetic field! You will start to see orbits on Fermi surfaces!!! (yes, I'm taking a few liberties here.)
Nah, I don't think Poynting theorem has any mud in it. Nonclassical ED - even the semiclassical one, on the other hand, is a never ending bog of mud and quicksand.

[adx]

Bit late but better post before it gets later...

If engineers are so dumb these days as you say, why do they get into discussing things they not only do not understand, but, worse, also don't want to understand?

Oh! Of course! They're dumb.

Maybe the average IQ of engineers is dropping as governments worldwide seem desperate to pump up careers in "ICT"? But I'd be more worried about the increasing proportion for whom it is really not their calling, rather than some synthetic measure of imbued stupid. And it would be a terrible generalisation to apply to individuals. There's differences between not being able to understand, not wanting to understand, not having the time, having other academic priorities etc.

Re-bringing up my comparison to medicine, few doctors are going to remember or use details of molecular biology or anatomy, which is arguably as fundamental and unchanging as classical EM theory. They might still want to discuss things from their training, over a few beers, while performing an easy surgery (oops not that last bit). These won't be 'teaching quality discussions'.

That's just belief at work. The dubiously existent backfire effect. Maxwellians have been equally triggered by comments which go against their worldview.

Have you heard of an Einsteinian? If someone calls your attention to the fact that you might be making mistakes because you don't really understand the theory of relativity, you call this person an Einsteinian?

There's no such thing as a "Maxwellian". Maxwell's equations are the theory of everything classical electromagnetism. Everything that is classically electric/magnetic has to be checked against this theory and, if it fails, dismissed right away.

So Maxwell's equations are not a worldview, they are a theoretical tenet of our trade. That's why people get impatient when someone exhibits total ignorance of that fact and claims to be an electronics engineer at the same time. That's cringe worthy and embarrassing.

The word is "relativists" (or similar). They were considered 'alternative' - not so much because of any belief Einstein was wrong, but the establishment thought his theories of no great significance, or not worth upsetting the apple cart over. I can also use the term if I believe he was not wrong, but missing something. So yes, "relativist", or colloquially, "Einsteinian".

If it's not a worldview, and just a theory, then I can take it or leave it, without fear of others' impatience, cringe or referred embarrassment. There is something quite inconsistent with your argument.

Or I can accept it is beyond me, and by your argument that circuit theory etc is a subset of his theory, then rely on these tools.

Or I can look on it as fondly as I like, but reject the mathematics as intractable and unpleasant to my tastes.

And it really is intractable and not far off useless in the real world. The people pushing the 'high end' EM solutions are not coming to the party with the tensor calculus. (Who would go to that?!) The only point of Maxwell's equations existing, apart from existing applications (like radio, and QFT) is putting into numerical solvers. Engineers need not understand it quantitatively at all, because it is effectively useless.

It's a thought experiment. Thought experiments are designed to test the limits of a concept. You're not expected to really accomplish them. ...

I disagree it's a thought experiment. Apart from the impracticality of scale, it's an eminently testable and calculable physical circuit, using any number of currently acceptable tools and individual interpretations. (Yes Veritasium's video somewhat trickily conflates concepts but I think that's his entire point - he's trying to very validly support that clickbait title with proof that electrical energy flows in fields. Which it has to, if the light bulb turns on before 1 second. Which we know it does. I disagree that it follows that energy does not flow in wires, but that doesn't alter the proof of concept Derek provides to blow minds.)

Avoiding Maxwell is not an option. Whether you are aware that what you doing is described by his theory or not. He's inescapable.

Many things I might do are described by many theories people may hold and that I may or may not be aware of. That does not mean I'm using them! If I grow wings and become capable of flight (and do fly), that isn't because of some cosmic permission granted by the author of a theory of flight. It’s not a capability imparted to me by birds (unless my abilities come from observations of birds and what they do with their wings - in that sense Maxwell is responsible for radio, but he was also responsible for trichromatic colour photography, arguably as useful as radio). He doesn't stand alone (nor do his achievements, in the sense that I'm not aware of a gaggle of "Maxwellians" going round insisting that 'His' image is displayed on the corner of all RGB Bayer arrays - but where can I sign up?!).

[adx]

...
Or, if you want to fly a bit lower, Kraus

John D. Kraus
Electromagnetics 2e
section 10.20 Circuit Applications of the Poynting Vector
p. 416
on p. 418, after considering a circuit with a battery (DC) and a resistors he writes:

"In Fig. 10-19aflow lines of the Poynting vector (power flow lines) are shown. It is evident that the power flow is through the empty space surrounding the circuit, the conductors of the circuit acting as guiding elements. From the circuit point of view we usually think of the power as flowing through the wires but this is an oversimplification and does not represent the actual situation."

This (italics mine). Is an example of an academic sermonising scientific hypothesis as fact. It may seem harmless, but results in generations(s) of disciples believing stuff.

[SandyCox]

There’s nothing wrong with Maxwell’s equations. The problem is the misinterpretation of what the Poynting vector tells us. Here is what Haus and Melcher says in Section 11.3 of their book:

"we illustrate the danger of ascribing meaning to S evaluated at a point, rather than integrated over a closed surface."

They are using an alternative energy flux vector S, not the Poynting vector.

Starting with conservation of energy, looking at the energy in a volume of space, you get the change in that energy by integrating an energy flux over the surface of the volume.  The form you choose for that flux may be arbitrary.  If there are no sources or dissipation of energy in that volume, you may have zero flux on the surface or you may have equal flux going in as going out.

They chose an alternative definition of energy flux that only depends on current density.  It still satisfies energy conservation.  But it only works in certain cases.

Clearly it doesn't work for a propagating wave in free space.

The Poynting vector seems to work for all cases.  So why use two different definitions of energy flux?

I attach the relevant pages from Haus and Melcher. They use the standard Poynting vector S=ExH in Example 11.3.1. They only introduce their alternative formulation after Example 11.3.1. Let's assume that the Poynting vector does indicate the path along which power is transferred. Then what is the mechanism that causes power to be transferred from the washer-shaped conductor to rod in this example?

The problem is that humans misinterpret the meaning of the Poynting vector. It has no meaning without taking the integral over the surface of an enclosed volume.

[SandyCox]

It's only been observed for very small particles (notwithstanding the mentioned recent experiments, which are interesting, but for which I'm still prudent.) And as I said earlier, any theory that can't survive observation under certain conditions can't be claimed to be valid for those conditions. So, while many physicists believe that the same laws hold at any scale, the honest ones will tell you that they just don't know. That it appears plausible, but we have no proof. The others are believers.

OK, I see our point of departure is at the definition of 'failure' of a theory.  So you are saying that if the theory is not feasibly falsifiable, we should remain skeptical.  OK, so it is not currently possible to experimentally verify the de Broglie wavelength of a tuna swimming in the sea, so your position is that we should regard any theoretical statement of it as unproven.  That's not an inherently unreasonable position, but keep in mind that it then also applies to common laws that we accept will apply universally, or at least over a broad set of conditions that we don't expect to be able to analyze experimentally.  I don't see QM/QED as being any different than any other physical laws or models in that regard.  It is verifiable until you simply reach experimental limits.  It's not like string theory, which AFAIK has not made any experimentally falsifiable conclusions.

This is an interesting setup, but it isn’t DC. As soon as the magnetic starts moving, the magnetic flux changes with time, inducing a time-varying voltage across the coil.

[adx]

The problem is that humans misinterpret the meaning of the Poynting vector. It has no meaning without taking the integral over the surface of an enclosed volume.

This sounds like what I was getting at in the last section of this post:
https://www.eevblog.com/forum/chat/veritasium-(yt)-the-big-misconception-about-electricity/msg3855821/#msg3855821

(Incompletely integrating) the Poynting vector is kind of a self-fulfilling prophecy (always works), because magnetic field is defined everywhere current isn't, and electric field is defined everywhere electric potential isn't. And for both electric fields (point charges) and magnetic fields ('monopole' fields like 1A going through an infinitely long wire), effect does not reduce over space (in the sense that 1/r^2 and 1/r relations are kind of an illusion due to things appearing smaller when they get further away).

But I don't know about the washer and rod situation yet, the reference a bit too 'math dense' for me to get a grip on without more thought. Which is not something I can guarantee!

[SilverSolder]

Arguably, you are storing potential energy while moving the magnets closer?  - and when they are standing still...  that energy is still there!

If the magnets are aligned so as to attract, it takes negative energy to move them into position from any further position or as physics teachers would posit, from infinity.

Ah, but since energy cannot be created or destroyed, the universe must have put the "negative" energy into them in the first place - you are just taking it back out again!  (and if you put the magnets back where they were, you would have to put that energy back!)

Fundamental law of the universe:  "No matter which way you turn, your ass always points backwards!" 

[Sredni]

There’s nothing wrong with Maxwell’s equations. The problem is the misinterpretation of what the Poynting vector tells us. Here is what Haus and Melcher says in Section 11.3 of their book:

"we illustrate the danger of ascribing meaning to S evaluated at a point, rather than integrated over a closed surface."

I attach the relevant pages from Haus and Melcher.

The full text is also online:
http://web.mit.edu/6.013_book/www/chapter11/11.3.html

They use the standard Poynting vector S=ExH in Example 11.3.1. [snip]
Let's assume that the Poynting vector does indicate the path along which power is transferred. Then what is the mechanism that causes power to be transferred from the washer-shaped conductor to rod in this example?

And what seems to be the problem?
The fact that you have lines going from a resistor to another resistor?
This is a kind of unusual geometry: we have a battery whose pole is directly connected to two resistors and then a perfect conductor shorting the other ends of these resistors.
Let's see if we can untangle the geometry and still see a problem. Consider this other example:


source: https://www2.oberlin.edu/physics/dstyer/CircuitSurveyor/help.html

The problem is that humans misinterpret the meaning of the Poynting vector. It has no meaning without taking the integral over the surface of an enclosed volume.

Is the fact that the first resistor in the above figure is getting all the field lines coming from the battery what you find of concern?

[Sredni]

Of course not and that is just another of your ridiculous straw men.  The cable needs to dissipate the power associated with the required current and the cable's resistance.  Somehow determining that by calculating Poynting vectors and an S-field would be the most ludicrously obtuse way that I can think of. 

I didn't say you need to use Poynting. I said: if all you are interested in are voltages and current you can as well ignore where the power is flowing - in the space? in the cables? in the delta dimension between hyperspaces? who cares? - and just use V*I to compute your sock's power. You don't need to know the details of surface charge distribution on the surface of the conductors and resistors in your circuit to determine that the electric field inside is constant and follows the local form of Ohm's law, so that you can use voltages and currents in your circuit. But even if you choose to ignore that charge distribution because "it does not do anything for you", that does not make that charge disappear.

[vad]

Thanks I am the one who made this video.

Thank you professor for making this video, and deriving Coulomb's inverse square law (one of Maxwell's equations - the Gauss' law) from QED.

I have a question though. Consider the following experiment. Let's take a rubidium laser, shine its beam through a beam splitter, then one of the beams goes through a thick copper plate to a detector A, and another beam goes through the air unobscured directly to a detector B (sea level, 25C air temperature, 30% relative humidity). Can I assume that the probability of a photon reaching detector A (the one behind the metal plate) would be 999999 times higher than probability of reaching detector B, considering the same Coulomb's law and QED?

PS. Simplified version of this experiment can be reproduced by every member of this forum with a flashlight and a frying pan.

[SandyCox]

There’s nothing wrong with Maxwell’s equations. The problem is the misinterpretation of what the Poynting vector tells us. Here is what Haus and Melcher says in Section 11.3 of their book:

"we illustrate the danger of ascribing meaning to S evaluated at a point, rather than integrated over a closed surface."

I attach the relevant pages from Haus and Melcher.

The full text is also online:
http://web.mit.edu/6.013_book/www/chapter11/11.3.html

They use the standard Poynting vector S=ExH in Example 11.3.1. [snip]
Let's assume that the Poynting vector does indicate the path along which power is transferred. Then what is the mechanism that causes power to be transferred from the washer-shaped conductor to rod in this example?

And what seems to be the problem?
The fact that you have lines going from a resistor to another resistor?
This is a kind of unusual geometry: we have a battery whose pole is directly connected to two resistors and then a perfect conductor shorting the other ends of these resistors.
Let's see if we can untangle the geometry and still see a problem. Consider this other example:


source: https://www2.oberlin.edu/physics/dstyer/CircuitSurveyor/help.html

The problem is that humans misinterpret the meaning of the Poynting vector. It has no meaning without taking the integral over the surface of an enclosed volume.

Is the fact that the first resistor in the above figure is getting all the field lines coming from the battery what you find of concern?

Thank you for this example. It makes my point even clearer. According to the Poynting vector, energy is transferred from one resistor to the other. We know this isn’t what is happening. Energy is transferred from the source to each resistor and not from one resistor to the other!

[SiliconWizard]

As rfeecs noted, a big chunk of the discussion is, in the end, really about a chicken-and-egg problem. So it can virtually go on forever. And Derek is a marketing genius.

[bsfeechannel]

If I grow wings and become capable of flight (and do fly), that isn't because of some cosmic permission granted by the author of a theory of flight.

You don't get it. There is a phenomenon that your dumbed-down understanding can't explain.

-- Here, take this theory, it explains it in clear terms what is going on.
-- Oh no, I'm an engineer, I cannot see the world except through my dumbed-down understanding. In fact, I'm going to declare that this phenomenon doesn't exist and who says that it does is wrong.

Give me break.

This kind of mindset is stupid. Especially in the case of engineers who are thought this bleep in their respective degrees.