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

[Sredni]

Yes, I'm aware of Feynman's explanation of radiation pressure - that's why I question the statements Naej is making in their interpretation of Carpenter. After all, Feynman remarks a moment later,

Therefore the force, the “pushing momentum,” that is delivered per second by the light, is equal to 1/c times the energy absorbed from the light per second! That is a general rule, since we did not say how strong the oscillator was, or whether some of the charges cancel out. In any circumstance where light is being absorbed, there is a pressure. The momentum that the light delivers is always equal to the energy that is absorbed, divided by c:
⟨F⟩=dW/dtc.(34.24)
That light carries energy we already know. We now understand that it also carries momentum, and further, that the momentum carried is always 1/c times the energy.

Carpenter denies there is any experimental evidence that light carries momentum:

The most obvious is momentum. The idea of electromagnetic
radiation carrying with it a momentum, and
hence exerting a force on any absorbing surface, epitomises
the properties which are customarily taken as
direct experimental evidence of the existence of the field.
But, as is well recognised [4-9], these properties are
unsupported by any evidence which is independent of the
way in which they are defined.

I'm not buying it.  I suppose he means that the way he defines things, it is charges acting on each other at a distance rather than fields acting on particles.

This would require reformulating lots of physics since Maxwell.

I printed the paper but I haven't read it yet. Just skimmed through it and also to the letter at the end.
Anyway, regarding the balance of momentum in a static system I have found interesting an example in Zangwill

Application 15.3 "The hidden momentum of a static system" p. 521

You might find it interesting as well.

[Naej]

Yes, I'm aware of Feynman's explanation of radiation pressure - that's why I question the statements Naej is making in their interpretation of Carpenter. After all, Feynman remarks a moment later,

Therefore the force, the “pushing momentum,” that is delivered per second by the light, is equal to 1/c times the energy absorbed from the light per second! That is a general rule, since we did not say how strong the oscillator was, or whether some of the charges cancel out. In any circumstance where light is being absorbed, there is a pressure. The momentum that the light delivers is always equal to the energy that is absorbed, divided by c:
⟨F⟩=dW/dtc.(34.24)
That light carries energy we already know. We now understand that it also carries momentum, and further, that the momentum carried is always 1/c times the energy.

Carpenter denies there is any experimental evidence that light carries momentum:

The most obvious is momentum. The idea of electromagnetic
radiation carrying with it a momentum, and
hence exerting a force on any absorbing surface, epitomises
the properties which are customarily taken as
direct experimental evidence of the existence of the field.
But, as is well recognised [4-9], these properties are
unsupported by any evidence which is independent of the
way in which they are defined.

I'm not buying it.  I suppose he means that the way he defines things, it is charges acting on each other at a distance rather than fields acting on particles.

This would require reformulating lots of physics since Maxwell.

Yes. He says momentum, which is just like energy, is just as arbitrary. You can observe a charge at point A accelerating a charge at point B but you can't tell from the experiment whether:
- the charge A transferred momentum to the ether, which then transferred momentum to the charge B
- the charge A lost momentum; the charge B gained momentum.

Sredni: yes this can also be seen as the potential momentum of the charge, which is a far simpler computation.
See equation 15 in https://physics.princeton.edu/~mcdonald/examples/thomson.pdf
If you don't believe me that momentum is arbitrary, you can read the conclusion of Zangwill's 15.8.3 right after.

[SiliconWizard]

Let's insert another coin.

Why is it that to illustrate the fact that the energy would flow "in fields" rather than "in wires" (again, whatever that really means), you have to resort to a transient phenomenon, and that you can't observe it at DC?

Can you transfer energy from one wire to another distant (but unconnected to the first) one, at DC steady state? If you can't, why? =)
And if you can, how close would the wires have to be?

[adx]

Let's insert another coin.

Why is it that to illustrate the fact that the energy would flow "in fields" rather than "in wires" (again, whatever that really means), you have to resort to a transient phenomenon, and that you can't observe it at DC?

Can you transfer energy from one wire to another distant (but unconnected to the first) one, at DC steady state? If you can't, why? =)
And if you can, how close would the wires have to be?

Me? Small coin, brief energy for now.

Because: It is the nature of it. The wave solution is waves, and manifests as transient, even at DC. The transient phenomenon I drew attention to is pure, unadulterated, 100% DC except for the tiny end of the signal extending into space. If ignoring the mathematical fields, all the effect happens (at this end) over the scale of angstroms. I was hopefully careful enough to limit my description to in the transmission line so it can properly be called "DC". Sredni's post talks of a single electron (or "a charge") moving at constant velocity as essentially DC. Which it is. But it isn't at all when you think about it (it's a travelling Dirac pulse, the very antithesis of DC). So yes, you can transfer energy from one wire to another at DC steady state and it happens all the time. The field effect does not reduce with distance, that is an illusion caused by objects appearing smaller as they go further away in space(time), so there is no limit to the spacing.

My point being that the "waves are strange" vs force times distance for charge carriers contexts are different.

[SiliconWizard]

So yes, you can transfer energy from one wire to another at DC steady state and it happens all the time.

Can you show us? =)

The field effect does not reduce with distance, that is an illusion caused by objects appearing smaller as they go further away in space(time), so there is no limit to the spacing.

That's quite fascinating. Can you show us?

[Bud]

That is because " Engineers are essentially dumbed-down "physicists". "
 

To me it is the other way around. Engineers spend time at the whiteboard writing equations and then go to the bench and use the soldering iron and physical artefacts to proof the model. Physicist only spent time at the witeboard writing equations unable to prove in real world, and therefore they are dumber than engineers.

[ogden]

That is because " Engineers are essentially dumbed-down "physicists".

To me it is the other way around. Engineers spend time at the whiteboard writing equations and then go to the bench and use the soldering iron and physical artefacts to proof the model. Physicist only spent time at the witeboard writing equations unable to prove in real world, and therefore they are dumber than engineers.

Time out

Scientists are indeed capable of doing experiments and proving them in real world, yet they are less experienced in real world applications compared to engineers. On contrary engineers are not that experienced in whiteboards. In short: both are needed. Best innovations usually come out of teams containing both kinds of professionals - scientists and engineers.

[ogden]

Can you transfer energy from one wire to another distant (but unconnected to the first) one, at DC steady state? If you can't, why? =)

Sure. Electron beam it is. Reference: vacuum tubes, CRT monitors.

[SiliconWizard]

That is because " Engineers are essentially dumbed-down "physicists". "
 

To me it is the other way around. Engineers spend time at the whiteboard writing equations and then go to the bench and use the soldering iron and physical artefacts to proof the model. Physicist only spent time at the witeboard writing equations unable to prove in real world, and therefore they are dumber than engineers.

I was merely quoting someone else here. In a tongue-in-cheek way. It seems to be getting more reaction when I post it, though.

As I said in the other thread, I do not even think this is true in general. That would assume "physicists" (as if, btw, it covered a homogenous reality) are a "superset" of engineers, thus being able to do the same things, and of course, more. Which is only marginally the case, and can't be generalized.

[bsfeechannel]

That is because " Engineers are essentially dumbed-down "physicists". "

LOL Quite accurate. Engineers are taught to be effective - to *not* dig into deep details of underlying physics and calculations as long as simplified model gives results within target tolerance.

Nope. Engineers are taught to build machines, structures, systems, etc. And if required dig deep in the underlying physics and calculations. These days they resort oftentimes to simulations and other tools, but they need to understand the meaning of the data they are inputting  and know how to interpret the results. They get the appropriate training for that in their degrees. Of course there are all kinds of specialization and post-graduate courses in engineering, but many can get away with their basic education. My experience has shown me that knowledgeable engineers are highly esteemed in the industry because they help solving problems much quicker and with much more precision. And that's efficiency.

[adx]

Lets have two slides with almost no friction and with the same slope. One is at one meter above ground level (plus the minimum height to get the minimum slope to compensate for friction), the other is at 100 meters above ground. We make two one ton stones slide for 1 km to their destination: a machine that will make the block fall and turn all gravitational potential energy into heat (eat your heart out, Carnot!).

The block falling one meter generates m g (1 meter) J of energy. The block falling 100 meters generates one hundred times that energy.
Has the energy travelled along the slide?
Both slides are identical, both stone blocks are identical, and the both moved at the same speed on the slide.

Has one slope really carried 100 times the energy of the other one? ...

It has to carry the same, and it has to be the absolute amount of energy, so any expenditure of energy comes off what it was sent with, solving the paradox of unknown potential or unrealisable energy. If the block is returned over the direction of "travel" then relative energy is easy to define.

[SilverSolder]

Lets have two slides with almost no friction and with the same slope. One is at one meter above ground level (plus the minimum height to get the minimum slope to compensate for friction), the other is at 100 meters above ground. We make two one ton stones slide for 1 km to their destination: a machine that will make the block fall and turn all gravitational potential energy into heat (eat your heart out, Carnot!).

The block falling one meter generates m g (1 meter) J of energy. The block falling 100 meters generates one hundred times that energy.
Has the energy travelled along the slide?
Both slides are identical, both stone blocks are identical, and the both moved at the same speed on the slide.

Has one slope really carried 100 times the energy of the other one? ...

It has to carry the same, and it has to be the absolute amount of energy, so any expenditure of energy comes off what it was sent with, solving the paradox of unknown potential or unrealisable energy. If the block is returned over the direction of "travel" then relative energy is easy to define.

If we ignore that G varies with altitude....   

The gravitational potential energy of the blocks is converted to kinetic energy as they accelerate down the slides.  The OP does not explain what happens to the kinetic energy of the blocks at the end of the slide... (do they hit a sand pit?)  but is there any doubt that the energy "followed the blocks" and traveled from the top to the bottom of the ramps?

[TimFox]

G is the universal gravitational constant, and does not vary with altitude.
g is the acceleration of gravity, and does vary with altitude.

[adx]

The gravitational potential energy of the blocks is converted to kinetic energy as they accelerate down the slides.  The OP does not explain what happens to the kinetic energy of the blocks at the end of the slide... (do they hit a sand pit?)  but is there any doubt that the energy "followed the blocks" and traveled from the top to the bottom of the ramps?

I took it to be that the kinetic energy was small enough to not be important (there to stick with the analogy of resistance in wire, show that part of the experiment is the same, and block makes its way under its own steam). The difference is that one block dumps 100m of mgh of energy (and arguably had that extra to start), and the other only 1, plus subtle nonlinearities like you mentioned. We can go on about as much "potential" energy as we want, but the question is over whether the slide "carried" more energy. If you don't like the fact it is 100m higher, then allow the block to fall in a 99m hole and rest there until the end of the universe where this potential energy never becomes "real" (no work), and depending on the situation with the big bang, might never have been. This implies a weak form of acausality. Not mathematically because we can tack imaginary quantities in to match experiment, but conceptually, where the whole meaning of an energy flux rests. To add insult to injury, we don't get our blocks back, so we might not even know what happened to them. We don't know how long it took. Confuse-o-land.

[Sredni]

The gravitational potential energy of the blocks is converted to kinetic energy as they accelerate down the slides.  The OP does not explain what happens to the kinetic energy of the blocks at the end of the slide... (do they hit a sand pit?)  but is there any doubt that the energy "followed the blocks" and traveled from the top to the bottom of the ramps?

No,  the blocks slide at constant velocity at very low speed (ideally on a frictionless slide there is no need for a slope). They arrive at the machine with the same velocity (ideally near zero).
All the energy when falling is converted by the machine into heat, so the blocks reach the bottom with zero velocity.  Imagine the machine is the perfect brake.

The EM case has the following differences, tho.

1.  The charge carry a field that can significantly alter the overall field of the system (while a rock does not alter in a perceptible way the gravitational field of the earth - it will be essentially constant near the surface).
The electrons that travel along the wire contribute to maintain the dynamical equilibrium where there is an excess on one side of the resistor and a lack of charge on the opposite charge. It is this charge imbalance that creates the 'hole in the ground' - the potential difference that confer the electron the energy that will be lost into heat.

2.   Momentum and energy are not necessarily independent. For electromagnetic waves, it is well known that we have E = c p. What about the EM field of our system? I have read something interesting on Panofsky and Phillips bit I want to merge it with what I've read in Zangwill and right now I have zero time.

[adx]

So yes, you can transfer energy from one wire to another at DC steady state and it happens all the time.

Can you show us? =)

The field effect does not reduce with distance, that is an illusion caused by objects appearing smaller as they go further away in space(time), so there is no limit to the spacing.

That's quite fascinating. Can you show us?

Yes and yes. Though conveniently I've run out of time. I was going to draw some diagrams, starting with a vacuum - an Airflo model I'll have to check what type. And a few more calculable facts to check, lest I pull a John Titor.

[SilverSolder]

The gravitational potential energy of the blocks is converted to kinetic energy as they accelerate down the slides.  The OP does not explain what happens to the kinetic energy of the blocks at the end of the slide... (do they hit a sand pit?)  but is there any doubt that the energy "followed the blocks" and traveled from the top to the bottom of the ramps?

I took it to be that the kinetic energy was small enough to not be important (there to stick with the analogy of resistance in wire, show that part of the experiment is the same, and block makes its way under its own steam). The difference is that one block dumps 100m of mgh of energy (and arguably had that extra to start), and the other only 1, plus subtle nonlinearities like you mentioned. We can go on about as much "potential" energy as we want, but the question is over whether the slide "carried" more energy. If you don't like the fact it is 100m higher, then allow the block to fall in a 99m hole and rest there until the end of the universe where this potential energy never becomes "real" (no work), and depending on the situation with the big bang, might never have been. This implies a weak form of acausality. Not mathematically because we can tack imaginary quantities in to match experiment, but conceptually, where the whole meaning of an energy flux rests. To add insult to injury, we don't get our blocks back, so we might not even know what happened to them. We don't know how long it took. Confuse-o-land.

Let's ignore the variation in "g" for a moment.

We can't ignore the kinetic energy! Unless the friction is so high that the blocks never start moving at all, the blocks will start moving down the ramp, accelerating all the way until some terminal velocity at the end of the ramp.   

Energy cannot be created or destroyed, it can only be transformed into another form!  In the case of the blocks it gets converted into two separate new forms:  kinetic energy, and heat due to the friction.  Each has to be accounted for separately.


Re. block falling into a hole:  The block will keep accelerating the whole way down the hole.  The potential energy that it had at the top is constantly being converted to kinetic energy at each point along the way as its speed increases.  So it seems totally fair to say that the energy follows the block in this case too, no matter what point along the path of the fall you freeze time! 

[SiliconWizard]

So yes, you can transfer energy from one wire to another at DC steady state and it happens all the time.

Can you show us? =)

The field effect does not reduce with distance, that is an illusion caused by objects appearing smaller as they go further away in space(time), so there is no limit to the spacing.

That's quite fascinating. Can you show us?

Yes and yes. Though conveniently I've run out of time. (...)

Yes, this is convenient. =)

Vacuum tubes require heating (to a highish temperature) some material to "emit" electrons.
Note that I was merely talking about, say, two pieces of wire - ideally with zero resistance. Just like in the original circuit. With no significant heating.
The point was not to reinvent the vacuum tube. Now the alternative to heating that I know of (cold cathode) requires ionizing some gas, so it wouldn't work in a vacuum. But please elaborate, because I'm pretty sure I've missed something. Just keep in mind it shouldn't require more than "wires" in a vacuum.

The point, is, again, to see if the original example in Veritasium's video is really relevant in showing what was claimed when the system reaches steady state.

[SiliconWizard]

Energy cannot be created or destroyed, it can only be transformed into another form!

I suppose you are assuming conservation of energy, which holds if we consider an isolated system.
Is the universe an isolated system? I'm not sure this has been fully answered yet. =) But this sure goes beyond the points made in this thread.

[SilverSolder]

Energy cannot be created or destroyed, it can only be transformed into another form!

I suppose you are assuming conservation of energy, which holds if we consider an isolated system.
Is the universe an isolated system? I'm not sure this has been fully answered yet. =) But this sure goes beyond the points made in this thread.

Can you think of an example where energy is created or destroyed,  rather than transformed?  -  I have always thought it a very basic law of the known universe...

[TimFox]

At the quantum level, energy and time have an uncertainty relationship like momentum and position.
"Virtual" particles are created and die in very short times, temporarily violating the conservation of energy.

[EEVblog]

The point, is, again, to see if the original example in Veritasium's video is really relevant in showing what was claimed when the system reaches steady state.

The question was clearly intended toward getting the 1/c instant response.
The question could also of course be used to show transient behaviour without any reference to Poynting or Maxwell at all. It could be used as just interesting tricky circuit fundamentals question.

[adx]

Note that I was merely talking about, say, two pieces of wire - ideally with zero resistance. Just like in the original circuit. With no significant heating.
The point was not to reinvent the vacuum tube. Now the alternative to heating that I know of (cold cathode) requires ionizing some gas, so it wouldn't work in a vacuum. But please elaborate, because I'm pretty sure I've missed something. Just keep in mind it shouldn't require more than "wires" in a vacuum.

The point, is, again, to see if the original example in Veritasium's video is really relevant in showing what was claimed when the system reaches steady state.

Yes, that's exactly what I mean - wires, DC, vacuum, and Poynting. But it's hardly anything controversial or new it turns out. I even spelled it out a fair few pages back but no one seemed to notice so I left it hidden in plain sight in the hope I might work it out. More a technicality of the wording, than any useful power transfer unfortunately! What I was more interested in was deriving something Poynting-like to illustrate why that weirdness works. But I think my "Got it" post is far more useful, the key to that is the energy moves along at the speed of light. Some weeks back now I worked out (didn't post) the longitudinal wave (acoustic) velocity of the electron fluid in a wire if acting on its neighbours only, based on the assumption of compressibility same as bulk metal (where the effect is basically that) and rest mass of electrons rather than whole metal ions. That is much slower than the speed of light, which shows that there has to be some longer-range field / interaction effects. The Poynting vector is of a phenomenon that travels at the speed of light, so can't be expected to have a direct physical relevance to something that moves slower. The energy has to transfer from each 'cell' (whatever that is) to the next at the speed of light, whatever the frequency, if there is to be a "flow" of something tangible (rather than a "flux" of something intangible which we are desperately trying to avoid treating energy (and therefore matter) as). I'd guess, like most things wavey, that it is the sum of a whole lot of small contributions, like the way a line of circular point sources sums to produce a line wave, that produces the result. And electrons moving to offset fields that would otherwise show energy flow (because they are carrying it in a different form / view) makes it appear zero in the wire, not any fact that it is zero. This isn't about searching for an accurate model (which we have), but understanding of something that appears incorrect.

Oops, walltext. The second paragraph will have to wait. And some other replies.

[adx]

adx: if you follow Poynting then copper wires are the low-frequency equivalent of light fiber, a transformer is impedance matching, and a resistor is a low-frequency black-body.

I'm reasonably happy with that occult-like thinking. Metal is a shiny reflector, transformers are used in RF for purposes other than isolation, and a microwave-powered incandescent emitter might not be such a silly thing in some piece of equipment. But there comes a point where even the silliest engineer will reject something too silly for even their silliest of comedic senses .

For acoustic waves, half the energy is in the pressure, and half in the velocity (much like in light, half is in E, half is in B).

I'm fairly sure if I learned facts such as that (for E and B) and it was presented as something understandable, then EM would have made a lot more sense to me. Instead I got invisible mathematical concepts, and things like the graph you see so often repeated (with the arrows, that I can only assume is as utterly opaque to others starting from nothing as it was to me - no one says it is a graph of field strengths along the line of propagation, leaving less mathematically inclined people to guess it is a picture of some kind of magical aether strings being poked at by sharp sticks which physically wave about).

Anyway, the acoustic wave thing might help explain (to others and myself) about Poynting and the 'difference' between DC and steady state.

A hydraulic circuit works a bit like an electric circuit (balls in a pipe), so turning on a switch (opening a valve) allows pressure to 'flow' at the speed of sound to the load, and current flows at the same time. This description (and hence model) of course has little to do with the pieces of fluid that carry the pressure and end up in the load, it's about a pressure wave causing the molecules to accelerate and flow almost instantaneously (compared to how long it would take the fluid to go around the circuit). Once this transient settles, and flow becomes steady state, nothing changes in the nature of how energy is delivered to the load - it is still described by a transverse (between pipes) pressure difference being sent back and forth, and how fast all the fluid molecules are moving around the circuit. If either end changes the pressure, the other end will see it at the speed of sound. Same if poking at something with a stick. If modelling that, a wave effect governs that transfer of pressure at only two possible velocities: + and - speed of sound (to and from load). Anything which uses that model to calculate power, can only assume it travels at that same speed and from a transverse pressure difference. If DC steady state, there are still molecules pushing on each other electrically, with mass, and a limit to how quickly that can do work at the other end.

For a hydraulic circuit at DC it is easy(er) to poo-poo the notion of a Poynting-like vector where the current is represented by some out of pipe "field", because the momentum part of the wave transfer is due to the inertial mass of the molecules (which is thought to reside in the molecules and pipe). It also doesn't change, so the energy transferred via pressure isn't mediated by the mass (so you could then turn around and say it clicks over to infinite speed at exactly 0Hz).

But for an electrical circuit, the momentum arises from electrical field effects, which can be outside the wire. Because the momentum isn't located to inside the electron, it is possible that the field changes as it passes by other parts of the circuit - with no net energy change but more possibility for action than with a particle with internal inertia.

And oops that's me again for the night.

[bsfeechannel]

Derek has done an an entire video on how he is deliberately chasing the algorithm and views. he's quite up front about it and explains his reasons at 14:45 and I think they are solid. And I know he's genuine about wanting to get mainstream people into science.

I think the "clickbating" aspect of his videos are of secondary importance. In this other video he discusses how misconceptions restrain people's ability to learn. That's why all Vertitasium videos start discussing the misconception first and then they introduce the scientific concept about the topic, because he saw that, that way, people invest mental effort in watching his videos and actually learn.