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

[Naej]

tl;dr : energy flows in wires. Or in vacuum. Whatever.

Is the earth the center of the universe? YES, at least for 1500 years. If you don't live under a rock, you'll see that the sun, the moon, the stars and the planets all traverse the skies every day and every night around us. The planets have that little loop they do in their orbits, but that's all perfectly predicted by the theory of the epicycles.

If that is so, why don't we use it anymore these days? It is because Galileo pointed his telescope to Jupiter and it became pretty clear that calculating the orbits of its recently discovered moons would be a nightmare.

Galileo then came with the Galileo's invariance, a.k.a. Galileo's relativity, where all inertial frames are equivalent to each other and their results can be converted from one to another using Galileo's transformation.

This principle underpins Newtonian mechanics.

One century later, Carpenter arrives, in 1989.
If you know a bit of multivariate calculus, definitely read his papers: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.205.4488&rep=rep1&type=pdf  http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.205.4597&rep=rep1&type=pdf

What the author is basically saying is that engineers are too dumb to understand energy in the fields (fields are counterintuitive, current as a fluid is not) so the author suggests that we embrace a concept abandoned by Maxwell and Heaviside because of its incompleteness.

As Maxwell himself pondered in his treatise below:

547.] He [Faraday] observes, however, that 'the first thought that arises in the mind is that the electricity circulates with something like momentum or inertia in the wire.' Indeed, when we consider one particular wire only, the phenomena are exactly analogous to those of a pipe full of water flowing in a continued stream. If while the stream is flowing we suddenly close the end of the tube, the momentum of the water produces a sudden pressure, which is much greater than that due to the head of water, and may be sufficient to burst the pipe.

If the water has the means of escaping through a narrow jet when the principal aperture is closed, it will be projected with a velocity much greater than that due to the head of water, and if it can escape through a valve into a chamber, it will do so, even when the pressure in the chamber is greater than that due to the head of water.

It is on this principle that the hydraulic ram is constructed, by which a small quantity of water may be raised to a great height by means of a large quantity flowing down from a much lower level.

548.] These effects of the inertia of the fluid in the tube depend solely on the quantity of fluid running through the tube, on its length, and on its section in different parts of its length. They do not depend on anything outside the tube, nor on the form into which the tube may be bent, provided its length remains the same.

In the case of the wire conveying a current this is not the case, for if a long wire is doubled on itself the effect is very small, if the two parts are separated from each other it is greater, if it is coiled up into a helix it is still greater, and greatest of all if, when so coiled, a piece of soft iron is placed inside the coil. Again, if a second wire is coiled up with the first, but insulated from it, then, if the second wire does not form a closed circuit, the phenomena are as before, but if the second wire forms a closed circuit, an induction current is formed in the second wire, and the effects of self-induction in the first wire are retarded.

549.] These results shew clearly that, if the phenomena are due to momentum, the momentum is certainly not that of the electricity in the wire, because the same wire, conveying the same current, exhibits effects which differ according to its form; and even when its form remains the same, the presence of other bodies, such as a piece of iron or a closed metallic circuit, affects the result.

550.] It is difficult, however, for the mind which has once recognised the analogy between the phenomena of self-induction and those of the motion of material bodies, to abandon altogether the help of this analogy, or to admit that it is entirely superficial and misleading.

A Treatise on Electricity and Magnetism, 3d edition, J.C. Maxwell, pp 195-196.

a) Derek insisted you use a counterintuitive (but correct) understanding of energy flow in a context where it is poyntless, claiming other ones are wrong, without proving they are wrong.
b) everything else is incorrect, except possibly the engineering history of the first transatlantic cables.

Well, we can go back to the epicycles. It is intuitive and we don't even have to learn the counterintuitive laws of Newton. But the scientific paradigm shifted long ago, so saying that the earth is the center of the universe may sound like a misconception these days. Kids don't even learn about epicycles in school.

What Maxwell is saying is that magnetic momentum does not behave entirely like mechanical momentum. He is right.

Perhaps you didn't get the memo, but many scientists are using a terrestrial reference frame, where the origin is at the center of the Earth. And they will continue to do so even if you laugh at them shouting "epicycles!", as they are not impressed.

Now I can see that you did not come up with an example which contradicts the JV law. Can you guess why? (They don't exist.)
So perhaps you should learn physics until you can find one, instead of shouting epicycles.

[Sredni]

Enlarged text mine.
You've found comfort in a text from 1941? Ok, whatever makes you sleep well at night!

Dude, that's Stratton. One of the most cited textbooks in EM.
Do you think Poynting theorem has changed since then? No, it hasn't. In the context of classical electrodynamics Stratton, Schwartz, Panofsky & Phillips, and Jackson are "the" references. I've heard good things about Zangwill, "Modern Electrodynamics" -  I have not read it thoroughly, only a few pages here and there, though - but even if it is a 2012 text, do not expect it to say anything different from Panofsky Phillips or Stratton.

For example, Zangwill says that "The analogy between this equation and the continuity equation [...] reinforces the interpretation of the Poynting vector S as a current density of electromagnetic energy."
Regarding the circuit with a simple resistor it surprisingly goes even further: "It is clear from the diagram that energy flows out of the point dipole source, into the vacuum, and into the wire at every point along its length."

But he acknowledges the same points made by Stratton in 1941 and has a little paragraph that says "It may seem odd that the Poynting vector for a wire circuit does not predict energy flow parallel to the wire itself. This and other unanticipated features of some Poynting flows prompt some authors to define a Poynting vector using S = E x B/mu0 + curl X. The vector field X is chosen to make [the Poynting vector] point in more “natural” directions. The [above] definition does not disrupt Poynting’s theorem because the latter contains only ∇ · S. Relativistic considerations constrain, but do not completely eliminate, this arbitrariness in the definition of S.
There is no real problem in any event because the Poynting vector is not an observable."
Not different from what Stratton wrote in 1941.
And Zangwill is well aware of the progress made in physics since Pearl Harbour.

Point is: you have to choose a theory and stick to it.

Do you use voltages and currents, and consider current as a flow of charge carriers? Stick to classical ED (it automatically incorporates special relativity) and learn how to correctly apply Maxwell's equations (to the point of being able to tell that the Poynting vector does not point directly towards the battery - or even good conducting wires - at DC because you've seen a picture on Feynman where it points radially in, in a resistive wire).
Do you like to think of electrons in circuits as waves of probability? Stick to non-relativistic quantum mechanics. But forget about describing electrons moving inside the conductors and banging ions: it's a wave that's being scattered by the lattice potential. Then that parts in your videos where you say "engineers knows very well that..." becomes all false. Try to use QM consistently to describe EM phenomena and see how far you go in even the simplest circuit.
Are you ready to forgo semiclassical theories and wanna go full quantum? Then stick to QFT and start computing probabilities for everything. But then basically everything you said in your video becomes lies.

You can't have cake and eat it.

[bsfeechannel]

What Maxwell is saying is that magnetic momentum does not behave entirely like mechanical momentum. He is right.

And, because of that, the analogy of current flowing in a wire like a fluid in a pipe is flawed.

Perhaps you didn't get the memo, but many scientists are using a terrestrial reference frame, where the origin is at the center of the Earth. And they will continue to do so even if you laugh at them shouting "epicycles!", as they are not impressed.

Yes. Galileo showed that the center of the earth as a frame of reference is as good as any other frame of reference. I use it all the time.

Now I can see that you did not come up with an example which contradicts the JV law. Can you guess why? (They don't exist.)
So perhaps you should learn physics until you can find one, instead of shouting epicycles.

Cool, let's learn physics together then.

[EEVblog]

Are you ready to forgo semiclassical theories and wanna go full quantum? Then stick to QFT and start computing probabilities for everything. But then basically everything you said in your video becomes lies.
You can't have cake and eat it.

Yes you can.
You can use the tools that work for you in your circumstances AND also have a theoretical debate over whether energy actually flows inside or outside the wire.
Just like you can happily and accurately use Newtonian Theory for most stuff.
Once again, the fundmental question being asked here is whether or not energy flows inside or outside the wire.
You've been going blue in the face saying it's always outside the wire because Poynting and classical theory says so. Now when challenged with QFT you seem to be taking the tact of "whatever way you want to look at it".
Are you now willing to admit that energy may actually flow inside the wire, depending on which way you want to look at it?

[bsfeechannel]

tl;dr : energy flows in wires. Or in vacuum. Whatever.

I'm begining to think that Derek/Ponyting can no more correctly claim that the energy actually flows outside the wires than QFT says it flows mostly inside the wire.

You see? It is you that are saying that. What "QFT" professor said is just that the probability of an electron interacting with another in the wire is greater than that of an electron interacting with another one 1 m apart. You jumped automatically to the conclusion that the energy flows in the wires due to your bias.

That's how misconceptions spread.

The "QFT" professor said that her field of research is not related to QFT QED. I suggest you interview a specialist in the study of QED to analyze Derek's claims and provide an unbiased conclusion.

[Naej]

Yes it's flawed. So you have to correct your intuition about A, or compute the integral.

I mean you literally found no problem in Carpenter's proofs that energy flows in wires. Because it's correct. So just admit it, and move on.

Dude, that's Stratton. One of the most cited textbooks in EM.

Yes. Did he prove that it was wrong to say energy flows in wires? No.

But he acknowledges the same points made by Stratton in 1941 and has a little paragraph that says "It may seem odd that the Poynting vector for a wire circuit does not predict energy flow parallel to the wire itself. This and other unanticipated features of some Poynting flows prompt some authors to define a Poynting vector using S = E x B/mu0 + curl X. The vector field X is chosen to make [the Poynting vector] point in more “natural” directions. The [above] definition does not disrupt Poynting’s theorem because the latter contains only ∇ · S. Relativistic considerations constrain, but do not completely eliminate, this arbitrariness in the definition of S.
There is no real problem in any event because the Poynting vector is not an observable."

That's right it's not an observable. So you can claim that the energy flows in wires. And you can also claim that energy flows from battery to the lamp by going behind the Moon.

Point is: you have to choose a theory and stick to it.

Do you use voltages and currents, and consider current as a flow of charge carriers? Stick to classical ED (it automatically incorporates special relativity) and learn how to correctly apply Maxwell's equations

Yes.

(to the point of being able to tell that the Poynting vector does not point directly towards the battery - or even good conducting wires - at DC because you've seen a picture on Feynman where it points radially in, in a resistive wire).

No. It's not in Maxwell's equations. It's not about an observable.
There you can see 729 variants of Poynting's theorem. You do not have to know for each what it will give in the battery/resistor situation. This is poyntless.
https://physics.princeton.edu//~mcdonald/examples/variants.pdf

[EEVblog]

tl;dr : energy flows in wires. Or in vacuum. Whatever.

I'm begining to think that Derek/Ponyting can no more correctly claim that the energy actually flows outside the wires than QFT says it flows mostly inside the wire.

You see? It is you that are saying that. What "QFT" professor said is just that the probability of an electron interacting with another in the wire is greater than that of an electron interacting with another one 1 m apart. You jumped automatically to the conclusion that the energy flows in the wires due to your bias.

That's how misconceptions spread.

The "QFT" professor said that her field of research is not related to QFT. I suggest you interview a specialist in the study of QED to analyze Derek's claims and provide an unbiased conclusion.

I've used the word "probable" multiple times in relation to this. I may have dropped that word a few times becaus it's getting monotonous. And you kinda can when it's (for example) 99.9% probable it's inside the wire.
Yes, I've tried to do my own research and didn't get very far, but from what I've read, this seems to be what QFT predicts.

You guys don't seem to like it because it seems to predict contrary to what Poynting and classical theory predicts. All of you were all gung-ho beating everyone with a Poynting stick until QTF was brought up. Now it seems like the eyes are darting around, because maybe, just maybe, you might have been trumped.
And even Sredni is posting his own references that say "hmm, maybe it's not quite right/complete".

[Naej]

Once again, the fundmental question being asked here is whether or not energy flows inside or outside the wire.

Just to be clear: this is not a question which can be settled with experimental evidence (unlike what Stratton said or implied).
This is a case of: should you say that the origin is in the center of the Earth, or in the center of the Sun/Solar system.
And the correct answer is: it depends what you're doing, both are correct (until someone finds a flaw in Carpenter's computations… but don't wait for it).

[bsfeechannel]

A lot of the "debate" coming more from using different (or even vague) definitions and a philosophical approach of science rather than experimental, it can probably go on forever. =)
Just like with the KVL one.

The idea that energy flows in the wires creates a lot of problems. For example, a dipole antenna is just an open transmission line. People struggle to understand how the "electrical" energy flowing in the transmission line gets converted to "electromagnetic" energy that can travel in the free space. Wait a minute. Isn't the energy flowing in the transmission line already "electromagnetic"? If you understand that the energy is already in the fields in the space around the wires, it is easy to see that  what the antenna does is just to provide a convenient geometry for the fields to propagate with maximum efficiency. No magic is going on there.

I showed an example of transmission of energy with a linear DC motor. The movable part of the motor is not galvanically connected to the solenoid (the stator). Energy flowing in the wires does not explain how that's possible.

[Naej]

If you want to explain, you use Maxwell's equations.

If you want to tell a story/tale about energy then you can tell yours, or you can tell the following one: a dipole antenna has radiation resistance, so it takes the energy from the wire and removes it (not only in a ohmic way);  and a motor converts the energy coming from the wires into mechanical energy.

[bsfeechannel]

And the correct answer is: it depends what you're doing, both are correct (until someone finds a flaw in Carpenter's computations… but don't wait for it).

Just as the epicycles were also correct. However, as I said, no one uses this theory anymore because it brings a lot of complications to explain certain phenomena. The energy flowing in the wires can be correct, however, you'll have a hard time to explain how energy flows from the primary to the secondary of a transformer, for instance.

So, Carpenter's article is more of an exercise in how it would be easier to understand certain simple situations, using Maxwell's equations, had the pundits who shaped the classical electromagnetism we know today chosen to stick to the initial intuition that the energy is contained in the wires. He doesn't say how it would be complicated to explain the rest.

[Naej]

No one said it was very complicated to consider a battery as a 0Hz RF emitter.
But I'm glad you understand that energy flowing in wires is correct. As correct as Maxwell's equations, to be clear.

Now you're saying that energy flows from the primary to the secondary. Did you compute Poynting's vector? What is the result ?
Here's a McDonald quote: "This problem was posed by Siegman [1], which led to several conflicting responses [2, 3, 4, 5], all of which seem somewhat misguided". So don't look in McDonald's paper nor in Carpenter's and tell us.

[bdunham7]

The energy flowing in the wires can be correct, however, you'll have a hard time to explain how energy flows from the primary to the secondary of a transformer, for instance.

At steady-state DC, the energy flowing in the wires perfectly explains the flow of energy from primary to secondary, just as it also describes the radiation from dipole antenna.  There is none.  So what's the problem?

[bsfeechannel]

The energy flowing in the wires can be correct, however, you'll have a hard time to explain how energy flows from the primary to the secondary of a transformer, for instance.

At steady-state DC, the energy flowing in the wires perfectly explains the flow of energy from primary to secondary, just as it also describes the radiation from dipole antenna.  There is none.  So what's the problem?

OK. Fine. Stick to it. Until Derek posts a video with a battery, a switch, a piece of wire and a lamp and you don't know how to explain why the lamp will receive energy before the current manages to travel the whole extension of the wire, and you accuse him of being a troll, or worse, like others did.

[Naej]

@bdunham7: There's no problem in DC nor AC, he knows that energy flows in the wires, he just doesn't find it convenient.

And somehow we need to speak about Poynting's vector to know that current appears to flow through capacitors now?

[bsfeechannel]

You guys don't seem to like it because it seems to predict contrary to what Poynting and classical theory predicts. All of you were all gung-ho beating everyone with a Poynting stick until QTF was brought up. Now it seems like the eyes are darting around, because maybe, just maybe, you might have been trumped.
And even Sredni is posting his own references that say "hmm, maybe it's not quite right/complete".

That's not what we, whoever the "we" are, feeling (dislike).

For macroscopic events like the one proposed by Derek's thought experiment, Quantum and Classical ED converge. So what the "QFT" professor said tells only part of the story. She says she's not a specialist on the subject. So we need the complete picture if you're going down that rabbit hole.

[bsfeechannel]

Now you're saying that energy flows from the primary to the secondary. Did you compute Poynting's vector? What is the result ?
Here's a McDonald quote: "This problem was posed by Siegman [1], which led to several conflicting responses [2, 3, 4, 5], all of which seem somewhat misguided". So don't look in McDonald's paper nor in Carpenter's and tell us.

I read McDonald's article long ago. I didn't see anything problematic with it. In fact he shows the misconception (the responses [2, 3, 4, 5]) that the energy has to flow inside the transformer when it in fact flows around it.

he knows that energy flows in the wires, he just doesn't find it convenient.

As inconvenient as considering the earth flat. T'works for short distances. Fails in the long haul.

[EEVblog]

Once again, the fundmental question being asked here is whether or not energy flows inside or outside the wire.

Just to be clear: this is not a question which can be settled with experimental evidence (unlike what Stratton said or implied).

That's what I suspect.

[EEVblog]

For macroscopic events like the one proposed by Derek's thought experiment, Quantum and Classical ED converge. So what the "QFT" professor said tells only part of the story. She says she's not a specialist on the subject. So we need the complete picture if you're going down that rabbit hole.

I didn't suggest she was a major authority on this, she was just the first AFAIK to raise a QTF response to this.
As it turns out though, it seems she has published a book involving QFT
https://www.amazon.com.au/Quantum-Space-Time-Dynamics-Hontas-Farmer/dp/0578007320


And published a few things: https://www.researchgate.net/profile/Hontas-Farmer

It never occured to me that QFT might apply to this, I thought Poynting was the best explanation we had, and that the energy must flow outside the wire, but it seems I might have been wrong.

[bsfeechannel]

As it turns out though, it seems she has published a book involving QFT
https://www.amazon.com.au/Quantum-Space-Time-Dynamics-Hontas-Farmer/dp/0578007320

It is important to notice that QED (Quantum Electrodynamics) is one of the fields (pun intended) of QFT. She's a specialist in a different area: the gravitational field. For us, electronics engineers, QED is what interests us. That's why it is important to look for the insights of someone specialized in QED.

[EEVblog]

As an aside, I just found this video.

[Naej]

he knows that energy flows in the wires, he just doesn't find it convenient.

As inconvenient as considering the earth flat. T'works for short distances. Fails in the long haul.

Carpenter's theorem states that if Maxwell's equations are correct, then JV is a valid energy flow. And with JV, energy flows only in wires.

So either:
a) you find a flaw in the 3 lines proof of the theorem
b) you find a counter-example to the theorem
c) you compare Maxwell's equations to flat earth-theory.

Conclusion: the statement "energy flows only in wires" is correct.

Dave: could you transmit the first message to Derek please?

[EEVblog]

he knows that energy flows in the wires, he just doesn't find it convenient.

As inconvenient as considering the earth flat. T'works for short distances. Fails in the long haul.

Carpenter's theorem states that if Maxwell's equations are correct, then JV is a valid energy flow. And with JV, energy flows only in wires.

So either:
a) you find a flaw in the 3 lines proof of the theorem
b) you find a counter-example to the theorem
c) you compare Maxwell's equations to flat earth-theory.

Conclusion: the statement "energy flows only in wires" is correct.

But that can't be entirely true in the transient scenario. It's demonstrably true that energy reaches the bulb at 1m/c, and that can't go through the wire.
Am I missing something? Sorry, I have not been following this thread for 2 weeks.

Dave: could you transmit the first message to Derek please?

He's already been bombarded with enough information.

[SandyCox]

I'm still working through Farmer's papers.
In Farmer’s paper entitled:
“Electromagnetic energy and power in terms of charges and potentials instead of fields”,
equation (2) is the same as Haus and Melcher’s equation (24) from chapter 11.
So, the two are the same under static conditions.

My question is: how does energy flow from the battery to the resistor (bulb) under static (dc) conditions?
There is no displacement current nor induction under static conditions. How do we explain this flow of energy by relying on the concepts of electric and magnetic fields?

[Naej]

he knows that energy flows in the wires, he just doesn't find it convenient.

As inconvenient as considering the earth flat. T'works for short distances. Fails in the long haul.

Carpenter's theorem states that if Maxwell's equations are correct, then JV is a valid energy flow. And with JV, energy flows only in wires.

So either:
a) you find a flaw in the 3 lines proof of the theorem
b) you find a counter-example to the theorem
c) you compare Maxwell's equations to flat earth-theory.

Conclusion: the statement "energy flows only in wires" is correct.

But that can't be entirely true in the transient scenario. It's demonstrably true that energy reaches the bulb at 1m/c, and that can't go through the wire.
Am I missing something? Sorry, I have not been following this thread for 2 weeks.

Carpenter's energy flow goes from the battery to the wires connected to it.
Current "goes through" (and Carpenter's flow does the same) the capacitor, and on the other side, wires move energy into the bulb.
Yes the theorem is entirely true.