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

[adx]

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.

I guess I asked for that, so I will take it on the back / shoulder (where a punch would land if I were in the process of running away, but not motivated or focussed enough). You have a point and I should have sucked it up and done the math. When given a choice between "veggie maths" and the class taken by Roy Kerr, I should have stuck with the latter (I think I did some), and various other mild or moderate regrets associated with my academic "choices" (but it really was a one size fits all conveyor belt, except for aforementioned veggie maths).

But you know what I'm going to say:

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

QFT. Whatever comes next.

[bsfeechannel]

QFT. Whatever comes next.

Maxwell's equations and the Poynting theorem explain the phenomenon perfectly. But I have no problem with QFT. Maxwell's equations are just QFT for when the Plank constant is made zero. Or, if you prefer, when we have a large number interactions between particles. Since we are dealing with a macroscopic phenomenon, and not the interaction of a few particles, h = 0 is a good enough approximation.

[bsfeechannel]

And Derek is a marketing genius.

So are the others who said he is wrong. All of them have talked out of their butts. Lots of views. All opinion. No facts.

[bdunham7]

So are the others who said he is wrong. All of them have talked out of their butts. Lots of views. All opinion. No facts.

Like your post right there?

Maxwell's equations and the Poynting theorem explain the phenomenon perfectly.

Did I miss the post where you used those to accurately predict the behavior the circuit in question before experiments were done?  If I did could you link it for me or give me the reply#?  I apologize in advance if you did post such an analysis.  And I don't mean the trivial answer of 1m/c that despite allegations of engineers not understanding light speed due to dumbness, very few people here actually missed. 

[adx]

... Maxwell's equations are just QFT for when the Plank constant is made zero. ...

I know. That's why I said "like radio, and QFT" (I wrote that before all this QFT stuff came up over the last few days). QED essentially derives from Maxwell's equations, and QFT generalises on that, extremely effectively.

Yet, like it or not, QFT has provided a 'worldview' which assists in 'debunking' (intentionally being loose with that wording) Poynting's vector as a source of truth for power flow at DC, a situation which is not far off being untestestable. It would require the experimental capabilities of Henry Cavendish's Earth density determination squared.

[bsfeechannel]

So are the others who said he is wrong. All of them have talked out of their butts. Lots of views. All opinion. No facts.

Like your post right there?

Views? I have not published any videos about the subject. And haven't collected a single penny from it. How can I be a marketing genius?

Did I miss the post where you used those to accurately predict the behavior the circuit in question before experiments were done?  If I did could you link it for me or give me the reply#?  I apologize in advance if you did post such an analysis.  And I don't mean the trivial answer of 1m/c that despite allegations of engineers not understanding light speed due to dumbness, very few people here actually missed.

But, but, but, Derek did that in his video! Why should I redo what is already perfect?

[bsfeechannel]

Yet, like it or not, QFT has provided a 'worldview' which assists in 'debunking' (intentionally being loose with that wording) Poynting's vector as a source of truth for power flow at DC, a situation which is not far off being untestestable. It would require the experimental capabilities of Henry Cavendish's Earth density determination squared.

Debunking? You got to be kidding me. QFT in fact confirms the Poynting vector at DC or at any frequency. The idea that nothing is happening at DC so the energy cannot flow through the fields is a misconception. At DC, AC, whatever, the electrons are exchanging virtual particles. That's why energy flows in the fields, even if the fields are not changing or moving.

Dave thinks that the Poynting vector does not work at DC because he is a circuit-headed engineer. The only way he can think of the energy traveling through space is when you have AC or RF. At DC no worky, because capacitors, transformers, and antennas, which are the only devices he knows that allow the transmission of energy through space, block DC.

I understand what Dave feels because a lot of engineers have trouble to reconcile their practical experience with the underlying concepts of the physical phenomena they are dealing with. In fact this is not new. Since scientists started to study electromagnetism they were faced with the non intuitive character of this phenomenon and expressed their puzzlement in their treatises.

The Poynting vector is weird, but it is what is really going on there. Welcome to reality.

[Sredni]

Consider this other example:

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

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.

What I see here is that each resistor takes the energy that competes to it and let the rest go.
Much in the same way a partially absorbing glass will let most of the light through. Energy is still coming from the source, not the glass. (the main difference is that the wires makes it irrelevant what the positions of the glass pan--- the resistors are with respect to the source)

Energy is transferred from the source to each resistor and not from one resistor to the other!

And yet, if you consider the fact that in this system the magnetic field is uniform inside the loops (the circuit is a 2D slice of infinitely long cylindrical circuit to simplify the math), the direction of the Poynting vector is the same as that of the equipotentials of the electric field. And you cannot deny that the electric field is in the space between the resistors (there is none in the wires) and its configuration depends on the the surface charge on all resistors. The wires make it easier to 'conduct' the electric field at the resistors and do so with relaxation times, but once the surface charge has settled, the resultant field is in the space between resistors (and inside the resistors).

Enclose each resistor in a gauss surface and compute the net flux of S through that closed surface to find the power absorbed and you will see that each resistor is getting the power corresponding to V times I. Do the same with the battery and you will see that the battery is losing power corresponding to that absorbed by the three resistors, not the first one alone. Battery spits power out, resistors suck 'their' power in.

[rfeecs]

You can't argue with math.  The Poynting theorem derived from Maxwell's equations in 2 and half minutes flat:

[adx]

Enclose each resistor in a gauss surface and compute the net flux of S through that closed surface to find the power absorbed and you will see that each resistor is getting the power corresponding to V times I. ...

Do the same procedure on some space inside the loops but not where wires or resistors are. Then tell me how the result in any way supports the concept that "power doesn't flow in the wires"?

(Yes I'm aware of what will happen if you include some wire. That's not the question.)

[adx]

The Poynting vector is weird, but it is what is really going on there. Welcome to reality.

I think you're probably right. But that's not certain, and no amount of introspection on the mathematical details of some theory is going to answer that last part.

I get it now, and I can see the attraction. Some people just want to believe.

[Sredni]

Enclose each resistor in a gauss surface and compute the net flux of S through that closed surface to find the power absorbed and you will see that each resistor is getting the power corresponding to V times I. ...

Do the same procedure on some space inside the loops but not where wires or resistors are. Then tell me how the result in any way supports the concept that "power doesn't flow in the wires"?

(Yes I'm aware of what will happen if you include some wire. That's not the question.)

I guess we can get to the conclusion that vacuum does not absorb energy?
(I wonder what a QFT theorist would say about that...)

[bsfeechannel]

I think you're probably right. But that's not certain, and no amount of introspection on the mathematical details of some theory is going to answer that last part.

I get it now, and I can see the attraction. Some people just want to believe.

What is funny is that the Poynting theorem was independently studied by Oliver Heaviside, the same guy who developed the transmission line model, that you attempted, without success, to use to try to "debunk" Derek. His study of energy flow through fields is what made it possible for him to come up with the modern version of Maxwell's equations, without which we wouldn't have the transmission line model, nor the high frequency electronics we have today, from computers to radio.

[bsfeechannel]

[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.

Your simple experiment is so brilliant that the Poynting-haters didn't even realize it.

[bsfeechannel]

...
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.

I will let Maxwell talk. But you can see that already in the beginning of the 19th century scientists who discovered the electromagnetic phenomenon were beginning to suspect that energy didn't flow in the wires because of experimental data, not because of some "academic sermonizing scientific hypothesis".

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.

There you have it. Maxwell is the Veritasium of the XIX century.

[bdunham7]

The idea that nothing is happening at DC so the energy cannot flow through the fields is a misconception. At DC, AC, whatever, the electrons are exchanging virtual particles. That's why energy flows in the fields, even if the fields are not changing or moving.

Yes, in QFT the fields are explained as exchanging virtual particles.  But I think you missed the point of Farmer's video.  As she pointed out, those exchanges are much, much more likely to occur along the wire rather than across the space.  If you actually used QFT and math to map all that out, you would indeed get fields that would match up with classic EM and the results would not 'disprove' Poynting or anything else in non-QFT physics.  But, if you actually DID all that--and I'm sure you aren't--the resultant fields, Poynting vectors and S-fields would not look like much the dramatized versions we have been seeing here with big arrows going through space from a battery to a load (and, b/t/w, omitting the equally big arrow going the other way from the battery).

Now as far as Derek's video, you continually misstate what others have said in order to prove them 'wrong'.  I didn't agree with Dave when he called you a troll, but I'm starting to wonder.  If you were to open the ends up on the long pairs of wires, you know full well that no current would flow through the load in the fully settled DC steady state and no power would be exchanged over that space via virtual particles or Poynting vectors.  You know that full well not because you will examine it with math, Poynting, QFT or advanced physics concepts, but rather because you simply apply Ohms law just like the rest of us blockheads.

Dave thinks that the Poynting vector does not work at DC because he is a circuit-headed engineer. The only way he can think of the energy traveling through space is when you have AC or RF. At DC no worky, because capacitors, transformers, and antennas, which are the only devices he knows that allow the transmission of energy through space, block DC.

IIRC, Dave and almost everyone else here has not somehow stated that Poynting's Theorem is incorrect.  You keep bringing that up and it just isn't true.  However...

The Poynting vector is weird, but it is what is really going on there. Welcome to reality.

...I think you may be misinterpreting the meaning of the Poynting vector as opposed to the integration of the S-field over a closed surface.  Maybe.  I really don't know.  I'd have to think about that.  I'm not a Poynter.

But, but, but, Derek did that in his video! Why should I redo what is already perfect?

Because his answer was the trivial 1m/c 'gimme' that we all understand, despite you attempting to repeatedly claim we don't whenever we omit the obvious.

[bdunham7]

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?

I downloaded that and was unable to get it to run (yes I read the instructions) and apparently you haven't either since you just posted the sample shot.  I'm not sure that it is complete or accurate, but maybe it doesn't matter.  What happens if you disconnect the first resistor right at the two ends?

[bsfeechannel]

But I think you missed the point of Farmer's video.  As she pointed out, those exchanges are much, much more likely to occur along the wire rather than across the space.

What she said is that an electron has a much higher probability of interacting with another electron a billionth of a meter apart than with one 1 m away. Just that.

She says nothing about how this interaction will finally get to the lamp along a wire 300.000 km long with gazillions other electrons and protons. Not even how these electrons will rearrange themselves in the wire as a function of this interaction.

So her video was yet just another stunt to capitalize on the polemic generated by Derek's video.

Dave says that QFT contradicts Poynting, but it is in fact he who said that. Not QFT.

IIRC, Dave and almost everyone else here has not somehow stated that Poynting's Theorem is incorrect.

Dave says it doesn't apply to DC. He's wrong. But the issue here is not technical, as Maxwell himself pondered on. It's difficult to accept that an analogy that you held dear turns out in the end to be superficial and misleading.

[HuronKing]

...
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.

I know this was already a page ago, but can we pause for a moment to appreciate that John D. Kraus, the inventor of the helical antenna and corner reflector array, is being called a sermonizing academic?
https://en.wikipedia.org/wiki/John_D._Kraus

I mean, you can call him wrong, and you'd be wrong to call him wrong, but Kraus was hardly an ivory tower academic who didn't build anything practical... he used his exquisite knowledge of Maxwell's equations and Poynting theory to create entirely new types of antennas and waveguides - and all without numerical EM-simulators that we take for granted.

[SandyCox]

Let’s look at Haus and Melcher’s example 11.3.1 in more detail. We look at the example from the point of view of conservation of energy. We can calculate the power entering the washer from the voltage source. We can also calculate the power entering the rod from the voltage source.
We then use Poynting’s theorem to calculate the power that is dissipated in the rod and the power that is dissipated in the washer. It all ads up correctly. All the power that is delivered by the voltage source to the rod is dissipated in the rod.  All the power that is delivered by the voltage source to the washer is dissipated in the washer.
According to our misinterpretation of the Poynting vector, Fig 11.3.1 leads to the conclusion that power is being transferred from the washer to the rod through region (a). This simply isn’t happening.

[Sredni]

Let’s look at Haus and Melcher’s example 11.3.1 in more detail. We look at the example from the point of view of conservation of energy. We can calculate the power entering the washer from the voltage source. We can also calculate the power entering the rod from the voltage source.
We then use Poynting’s theorem to calculate the power that is dissipated in the rod and the power that is dissipated in the washer. It all ads up correctly. All the power that is delivered by the voltage source to the rod is dissipated in the rod.  All the power that is delivered by the voltage source to the washer is dissipated in the washer.
According to our misinterpretation of the Poynting vector, Fig 11.3.1 leads to the conclusion that power is being transferred from the washer to the rod through region (a). This simply isn’t happening.

We can say the same for the three parallel resistors: in the middle section we see lines of Poynting field coming out of the first resistor and getting into the second one. The first resistor is in the way of power transfer to the second resistor but is not the source of the energy (no more than the empty space between battery and first resistor is). Didn't Haus and Melcher warn the reader about the dangers of ascribing meaning to S evaluated at a point, rather than integrated over a closed surface?

And besides, you say

"All the power that is delivered by the voltage source to the rod is dissipated in the rod.  All the power that is delivered by the voltage source to the washer is dissipated in the washer."

The same happens with the parallel resistors: all the power delivered to the first resistor - which you can compute by integrating over a closed surface containing it - is dissipated in the first resistor (where else?)
In the convoluted geometry of H&M cylinder, washer and rod share the power delivered by the battery. Change the resistivity of the material and you should be able to have one glow red hot, while the other stays cool.

[Sredni]

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?

I downloaded that and was unable to get it to run (yes I read the instructions) and apparently you haven't either since you just posted the sample shot.

Yes, I downloaded it as well and got an error at runtime. But my laptop is so old that almost nothing works anymore. I am relieved to see I am not the only one not being able to run it.

I'm not sure that it is complete or accurate, but maybe it doesn't matter.  What happens if you disconnect the first resistor right at the two ends?

The total power deliver by the battery will be less, and the Poynting field lines will go through the region of space where the disconnected resistor is as if it were empty space.

Also, I see in another post someone - maybe you - noticed the absence of lines outside the circuit. This is a consequence of the 2D simplification to make computations easier. The circuit is a 2D slice of an infinite cylindrical circuit with infinitely long linear battery and infinitely long linear resistor. This will make the magnetic field much like that of an infinite solenoid: exactly zero outside and uniformly constant inside. This is why the Poynting field lines are directed as the electric field equipotentials.

You might argue that this is an unphysical situation, but it's at least a very reasonable approximation of finite length cylindrical circuits (much in the same way infinitely long solenoids are a reasonable approximation of finite length real-life solenoids). The difference with respect to a flat circuit in 3D is the magnetic field decreasing with distance from the conductor and its presence outside. The Poynting field will be present all around the conductors and will be stronger near them. Still, it will be in space between them.

[SandyCox]

Let’s look at Haus and Melcher’s example 11.3.1 in more detail. We look at the example from the point of view of conservation of energy. We can calculate the power entering the washer from the voltage source. We can also calculate the power entering the rod from the voltage source.
We then use Poynting’s theorem to calculate the power that is dissipated in the rod and the power that is dissipated in the washer. It all ads up correctly. All the power that is delivered by the voltage source to the rod is dissipated in the rod.  All the power that is delivered by the voltage source to the washer is dissipated in the washer.
According to our misinterpretation of the Poynting vector, Fig 11.3.1 leads to the conclusion that power is being transferred from the washer to the rod through region (a). This simply isn’t happening.

We can say the same for the three parallel resistors: in the middle section we see lines of Poynting field coming out of the first resistor and getting into the second one. The first resistor is in the way of power transfer to the second resistor but is not the source of the energy (no more than the empty space between battery and first resistor is). Didn't Haus and Melcher warn the reader about the dangers of ascribing meaning to S evaluated at a point, rather than integrated over a closed surface?

And besides, you say

"All the power that is delivered by the voltage source to the rod is dissipated in the rod.  All the power that is delivered by the voltage source to the washer is dissipated in the washer."

The same happens with the parallel resistors: all the power delivered to the first resistor - which you can compute by integrating over a closed surface containing it - is dissipated in the first resistor (where else?)
In the convoluted geometry of H&M cylinder, washer and rod share the power delivered by the battery. Change the resistivity of the material and you should be able to have one glow red hot, while the other stays cool.

I fully agree with everything you are saying. We are making the same point.
You are just applying Poynting’s theorem. Poynting’s theorem is absolutely correct.
The point I’m trying to make is indeed about the dangers of ascribing meaning to S evaluated at a point. People have incorrectly come the conclusion that the Poynting vector points to some kind of conduit through which electromagnetic energy is transferred. Ascribing meaning to the Poynting vector at a point leads us to the wrong conclusion, as shown by Fig. 11.3.1.
I’m not quite sure what you a trying to say by “glowing red hot”. Are you saying that energy is now transferred through thermal radiation?

[Sredni]

Ascribing meaning to the Poynting vector at a point leads us to the wrong conclusion, as shown by Fig. 11.3.1.

I didn't see Haus and Melcher recant what they wrote

"Even with the fields perfectly stationary in time, the power is seen to flow through the open space to be absorbed in the volume where the dissipation takes place."

Did you?

I’m not quite sure what you a trying to say by “glowing red hot”. Are you saying that energy is now transferred through thermal radiation?

No, I'm saying that by making rod and washer of very different materials you can have one glow red hot while the other stays cool, and viceversa. There still will be Poynting field lines in the space inside the can and they will account for the difference between the total power delivered by the battery and the power absorbed by the rod.
In one case you will see a lot of lines coming out of a cool washer to impinge into a red hot rod.

[adx]

... It makes my point even clearer. ...

Good point.

I'm wholly unsatisfied with that diagram as any sort of level-headed description for where the power "really" flows. It's warped and wrong-looking. This is not just intuition:

You've got a single-valued proxy for "current flowing around this loop", and a(n electric) field gradient which basically says "this voltage between these wires divides over this space in this way". That is to say, exactly(?) what I was saying earlier in that the power flow is a combination of moving charge carriers and potential difference. Except to map this out over space requires some fast and fancy guesswork. Kind of a geometrical mean between apples and oranges - which is what this diagram is. But that's not beyond someone with no appreciation of concepts like induction, capacitance, speed of light, EM etc to draw it up. All it requires is an extremely simplistic grasp on magnetics (not even any 1/r law), P= V*I, and an ability to graphically divide voltage up into equipotential lines.

So there's 2 problems for the statement that it is the true physical nature of power flow at DC:

1/ The only 'evidence' supporting its physical truth is that it works at AC, with induction, where a location for fields induced by said induction is defined by Maxwell's equations, leading to an easily testable idea of where the power is as it tries to travel over space. (And perhaps the fact that steady state doesn't really exist.) But in the situation that it looks wrong and warped as a model at DC, that's not enough to make it acceptable.

2/ My first guess to resolve the conundrum of where power flows if it must partly go as a difference between two paths of movement, gives the same result but as a self-fulfilling image of "the energy is here" based on rather uneducated guesswork. That's even less satisfying.