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

[Howardlong]

I wonder how many EEs, as opposed to physicists, have had a practical use for directly using Poynting vectors or Maxwell's equations since leaving university? Sure we all know the right- and left-hand rules, and an RF engineer might well have use them indirectly when using an EM or antenna modelling package, put I doubt most EEs will have touched them, or have had a need to do so directly, since leaving the classroom.

My job as an educator (and as a working professional mentoring interns) is to do my best to ensure they have the correct physics understanding of the underlying phenomena so they can apply it to ANY EM problem and arrive at the correct answer. They can make their own shortcuts and tools with this knowledge.

If you're educating engineers, I'd recommend not fixating excessively and unnecessarily on something they're unlikely to ever use, at the expense of something they will. Not to mention, it's pretty difficult to make dry theory engaging when there's not an immediately obvious practical use for it.

I'm doing a disservice to the profession of engineering if I handwave away Maxwell and say "well you'll never actually need this so I'm not going to show you where the shortcut comes from but just give you the shortcut..." and substitute the rote intuition of limited models applied to specific conditions for the actual physical theory whose simplifications have created the models.

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE. As an example, almost all of the ES & EM theory stuff I learned parrot fashion for my degree I've never needed to use since. That hasn't hindered me in designing satellite communication systems, whether it's the antenna, the feed, the LNA, the PA, the mixers, the oscillators, the filters, the quadrature modulators and demodulators, the modulation and coding schemes, or the firmware implementations.

There are reasons this theoretical knowledge gets tested to become a professional licensed engineer.

Except it's not clear to me what those "reasons" are, when compared to other more practical and applicable skills as an engineer.

I'm not suggesting that there is no place for Poytning, Fleming, Maxwell, Faraday etc in engineering, just that it's unlikely to be needed directly in the day job, and that academia places too much priority on them at the expense of other more useful skills to engineers.

At its extreme, it's perfectly possible in my direct experience to go through an entire electronics engineering degree without ever having picked up a soldering iron or used an oscilloscope.

[Bud]

Except it's not clear to me what those "reasons" are, when compared to other more practical and applicable skills as an engineer.

Because the people sitting in those committees are not practical engineers, they are academic rats.

[HuronKing]

Except it's not clear to me what those "reasons" are, when compared to other more practical and applicable skills as an engineer.

Because the people sitting in those committees are not practical engineers, they are academic rats.

Are you licensed? I'm curious what your experience is with the NCEES, the FE exam, or the PE exam, or any state/national licensing board for you to make this claim.

[bdunham7]

The first and most important thing an engineer should learn is: know the limits of your models.
You and Mehdi think the effect of the field propagating from the switch can be modeled by a transmission line that extends in the perpendicular direction? Think again.

Which fields?  If you are talking of the E-field from the positive battery terminal, it should already have propagated to the lamp because if it can propagate over 1 meter of space it can certainly propagate over the switch contacts (and no I don't mean leakage current).  There are no new fields propagating 'from the switch' when it is closed, all of the effects in this circuit are a direct result of current flow--yes, moving charges again--down the wires and the changing fields that result from that. 

As far models go, the transmission line model seems to pretty closely match the experimental results for the scaled-down versions.  And those that used the lumped-element model of a transmission line have acknowledged the limitations such as the spike from the capacitor being first (Mehdi) and the additional propagation delay across the line due to the model not incorporating physical size in that dimension (Dave Jones).  It's not like they're ignorant of these things.

[Bud]

I looked into becoming licensed but decided it was not worth it. It would not give me anything beside being out of $2000 each year in license fees and spam mail from the committee in my community mailbox with invitations to paid events. Now tell me where my $2000 were going to go, in whose pocket ?

[HuronKing]

I looked into becoming licensed but decided it was not worth it. It would not give me anything beside being out of $2000 each year in license fees and spam mail from the committee in my community mailbox with invitations to paid events. Now tell me where my $2000 were going to go, in whose pocket ?

Maybe Canada is a scam then. My fees are $180 every 2 years - not $2000 every year, lol.
Licensure was a requirement for my company to pay for me to be UL508A certified for panel inspections and labeling. I also used my license for eligibility for a government facilities EE role. I'm also involved in FE test prep and keep up on what's tested and what isn't.

[HuronKing]

If you're educating engineers, I'd recommend not fixating excessively and unnecessarily on something they're unlikely to ever use, at the expense of something they will. Not to mention, it's pretty difficult to make dry theory engaging when there's not an immediately obvious practical use for it.

I teach lab courses mainly. I cover 'dry theory' and immediately apply it. I derive the expression for transformer voltage from Faraday's Law and this stays with the course right to the very end where they learn about synchronous machines and DC generators. None of those machines can work without 'the dry theory.' I'm teaching future engineers how to apply physics to solve problems - not 'plug and chuggers.' Of course we create simplified models - but the theory supports the models to the extent that one can know when they don't work.

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE. As an example, almost all of the ES & EM theory stuff I learned parrot fashion for my degree I've never needed to use since. That hasn't hindered me in designing satellite communication systems, whether it's the antenna, the feed, the LNA, the PA, the mixers, the oscillators, the filters, the quadrature modulators and demodulators, the modulation and coding schemes, or the firmware implementations.

I do not agree that teaching how to apply Maxwell's Equations is 'teaching unnecessary details.'

Except it's not clear to me what those "reasons" are, when compared to other more practical and applicable skills as an engineer.

The first exam towards licensure is on the Fundamentals of Engineering. If you look at the list of topics they are... well... the fundamentals of engineering. I wouldn't want someone to have a license for EE who does not understand how to do a simple voltage phasor calculation or what it means.

I'm not suggesting that there is no place for Poytning, Fleming, Maxwell, Faraday etc in engineering, just that it's unlikely to be needed directly in the day job, and that academia places too much priority on them at the expense of other more useful skills to engineers.

Academia places emphasis on passing exams. I personally don't do that. I put emphasis on intuition for the un-intuitive - teaching students about how to learn and how to think about problems. I don't know what kind of engineering my students will end up doing (I personally thought I would do RF engineering, then got an MSEE emphasis in electronics, but have ended up doing control systems automation as a career). So, I teach them the principles and concepts that can be applied to any situation.

At its extreme, it's perfectly possible in my direct experience to go through an entire electronics engineering degree without ever having picked up a soldering iron or used an oscilloscope.

And mine too. And also to have never heard of "NEC" or "conduit fill" or "NEMA rating." I teach about those things too.

But - are we really talking about that? That sounds like a different problem - and engineering school is not technician school (even if there should be some skill overlap). I'm talking about teaching engineers the actual physics. Complaining that students don't learn about soldering irons is a red herring. As evidenced by the discussions about Veritasium's videos online, tons and tons of EEs graduate college, despite all the 'useless theoretical' emphasis they supposedly got, and STILL have no idea where the energy is flowing around wires...

Yea they'll continue to collect their salaries doing whatever they do with their degrees, which is fine of course, but it is not true to claim they understand EM.

[SandyCox]

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE.

Charles Inglis said the following:
'In brief, young people should learn at the university all those parts of electrical engineering which they cannot conveniently learn with us in industry: when they come to us, they should be  able to measure, to use mathematics, and they should be clear about the fundamentals. The rest is not part of the job of the University, and cannot be taught by it in the way that we need.'

[StillTrying]

Going back to the 1st post and video, shirley I could test this with a blue LED, photodiode and ~20m of wire.

I really was going to test it, using a 74AC14 as the fast switch and a 100R as the bulb, perhaps changing to a LED and photo diode depending on the result(s).
But I don't think I'll bother now that we know the answer and that someone's already tested it, although I've not found that post.

As a thought experiment I'm trying to figure what a H shape would do, I suspect the time delay in the bulb coming on would still be only the 1 meter delay time between the switch and and bulb, but that's just a poyntless guess.

[bdunham7]

However, if I ask an engineer, 'where is the energy in the coax cable?' and they respond 'in the wire' then I know they don't actually understand how it works

I can't think of anyone who would get that wrong as long as the problem is in the transmission line domain (not DC).  The discussion might be more interesting at DC.

Another good example of this is voltage transformation in a transformer. Yes - the turns ratio for voltage transformation is described by a simple fraction, but getting that fraction from Faraday's Law is quite interesting and provides tremendous insight into how AC asynchronous induction motors work

Well, showing the turns ratio vs voltage ratio is actually a trivial problem with Faraday's law once you lay it out (not to diminish the challenge of teaching it to students) but I'd be interested in how you extend that to induction motors at that level.  Most everyone seems to take induction motors for granted--and often incorrectly assume that they all share common performance characteristics--but the actual design of them is quite an art.  Or science. 

[bdunham7]

As a thought experiment I'm trying to figure what a H shape would do, I suspect the time delay in the bulb coming on would still be only the 1 meter delay time between the switch and and bulb, but that's just a poyntless guess.

Nice!  Sure, there will be an initial response in 3ns or so, but what happens after that might be interesting. 

[Vtile]

Most everyone seems to take induction motors for granted--and often incorrectly assume that they all share common performance characteristics--but the actual design of them is quite an art.  Or science.

Well if you calculate the difference on motor design shops vs motor implementation shop you soon notice why it is taken as granded another thing is that the Steinmetz model have been the de facto aproximation for ac motors past 100 years, so much that most even don't know anymore where that model originates. Luckily these days any well respected motor and drive manufacturer have a design tool where you can apply the process model (if it is known) to get the right model from hundrets if not thousands of models.

Btw. Another thing that is annoying is that Maxwell equations are referred ad Maxwell equations, while in reality those that are most often referred as Maxwell equations are actually Maxwell-Heaviside equations.

[Howardlong]

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE.

Charles Inglis said the following:
'In brief, young people should learn at the university all those parts of electrical engineering which they cannot conveniently learn with us in industry: when they come to us, they should be  able to measure, to use mathematics, and they should be clear about the fundamentals. The rest is not part of the job of the University, and cannot be taught by it in the way that we need.'

My point is about balance, and in my experience, far too much time and emphasis is put into topics that will remain irrelevant for the rest of an engineer's career at the expense of skills that really would be useful.

"they should be  able to measure"

Given the choice between an EE graduate who can solder up a circuit, use an oscilloscope, and one who's able to quote verbatim Maxwell's four equations, I'm 100% sure who I'd go for.

"to use mathematics"

Yes, although when most of the answers to analytic questions end up being some fractional portion of pi, one questions the relevance sometimes. ;-)

"and they should be clear about the fundamentals"

Yes, but it is the fixation on spending so much time on the details such as Maxwell, Poynting etc that in practice are almost only ever used by engineers indirectly in modelling and design tools.

To reiterate, I'm not suggesting that these are not taught, just that too much time and emphasis is spent on them when there are other skills that are so sadly lacking. It's the lack of balance I am concerned about.

[bdunham7]

Well if you calculate the difference on motor design shops vs motor implementation shop you soon notice why it is taken as granded another thing is that the Steinmetz model have been the de facto aproximation for ac motors past 100 years, so much that most even don't know anymore where that model originates. Luckily these days any well respected motor and drive manufacturer have a design tool where you can apply the process model (if it is known) to get the right model from hundrets if not thousands of models.

Yes, it is a mature and established art/science, the details of which are well understood by a relatively small contingent of engineers AFAIK.  So the solutions for various applications are all documented and motor engineers are probably not designing motors from first principles.  But I think a lot of people, even ones that should know better in my experience, don't realize the vast complexity and variety of induction motor characteristics.  For example, I've heard more than one person who should know better declare that all 3 phase motors inherently have high starting torque.  In one case such a person insisted on using a 3-phase motor unsuited for the task of starting a load with a lot of inertia, only to watch it burn up fairly promptly after not spinning up that load.

[Vtile]

Without clarity from Derek, my take is that the vagueness is deliberate: thus, I take it to be a trick question. Kinda disappointed to be honest, especially as the etymology for "veritasium" is rooted in the latin word for "truth". The more I think about it, the more I['m coming the the conclusion that the original video was more about clicks and engagement than it was about truth.

You don't have to guess at that, Derek himself did an entire video saying that going forward his videos were going to be optimised for viral views and clicks. He succeeded, he knew very well this would bring an avalance of responses from engineers. You can almost see the joy on his face as the professors told him he would get called out on it.

They didn't say Derek would be called out because engineers know best. Quite the opposite. Engineers are essentially dumbed-down "physicists". But that's not a problem. The problem is that most of them don't know that and some of them keep pestering physicists when physicists show them the limitations of their knowledge.

We, engineers, need to stop this. We need to acknowledge that physicists hold all the keys to our knowledge.

Well no, no, no put an physicist to work some practical engineering problems and find out. The same applies to your rather insightfull post as what Feinman said relationship between physicist and mathematicians.

[HuronKing]

However, if I ask an engineer, 'where is the energy in the coax cable?' and they respond 'in the wire' then I know they don't actually understand how it works

I can't think of anyone who would get that wrong as long as the problem is in the transmission line domain (not DC).  The discussion might be more interesting at DC.

Usually these types of questions would start in AC and go to DC. For example, students well understand a transformer when we talk about AC voltages. When I ask them what happens if a DC voltage is applied to the primary of a transformer, then they get confused, and after being confused, the physics becomes much more clear (and they suddenly learn why transformers are used for DC isolation in AV circuits, a practical application!)

Well, showing the turns ratio vs voltage ratio is actually a trivial problem with Faraday's law once you lay it out, but I'd be interested in how you extend that to induction motors at that level.  Most everyone seems to take induction motors for granted--and often incorrectly assume that they all share common performance characteristics--but the actual design of them is quite an art.  Or science.

Indeed it's trivial but it amazes me every semester how many seem so astonished when its laid out. Maybe they had the physics beaten out of them by the time they get to me - I dunno, lol.

As to extension to the induction motor, the extension comes from noting that an induction motor is, essentially, a transformer immersed in a rotating magnetic field. Ampere's Law and Faraday's Law together create the rotor action. This is a video I show in the class:


And this is what I use as a segue to talk about VFDs and harmonic reflection in motor control - again, in the context of Applied EM.
https://www.motioncontroltips.com/faq-what-are-vfd-reflected-waves-and-why-are-they-harmful/

My classes can't get into the designing of these machines from first principles (and that would be beyond my own expertise honestly) but I'd still like them to see how one gets from the fundamental laws to some really important *practical* ideas and problems one could encounter.

[snarkysparky]

Those who know Maxwell's equations may be using them unconsciously.  Same is true for many esoteric math thingies learned in Eng school.  Just because you are not conscious of using them doesn't mean they are not helping.

Suppose one didn't know how to add numbers.  A trip to the grocery store would be a nightmare.  Never knowing if you have enough to pay for your cart and not knowing how to find out. OR if you are being swindled.
But we all know how to add but rarely do we tally up our cart.  A gut feel is often good enough.

The concepts need to be understood by competent Engineers.

[HuronKing]

It's kind of interesting and surprisingly topical how Steve Mould has made this video on the assassin's teapot and has an excellent digression in the middle of it to talk about the usefulness of physical models, when they reach limitations, and why keeping the underlying theory in the back of your mind is important:

[tom66]

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE. As an example, almost all of the ES & EM theory stuff I learned parrot fashion for my degree I've never needed to use since. That hasn't hindered me in designing satellite communication systems, whether it's the antenna, the feed, the LNA, the PA, the mixers, the oscillators, the filters, the quadrature modulators and demodulators, the modulation and coding schemes, or the firmware implementations.

This, I don't really need to know how a P-N junction works.  I want to know how to apply a transistor and diode in a circuit, how they behave, what can go wrong, what configurations they work best in.

My university degree taught me a lot more about how a P-N junction works at the electron-hole model and how to fabricate my own and why quantum theory predicts X and Y behaviours.  I have zero interest in that as a day-to-day EE, and save for if they were planning on going into a semiconductor field, I think that would apply to any of my student colleagues. 

University is too focused on giving engineers a route to a PhD, when it should focus on making good engineers.  Tools like problem solving, systems design techniques, programming/software design, and understanding of lots of little things at a relatively shallow depth with the tools to learn more using the facilities we have (internet, library)

[bsfeechannel]

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE.

How can you say that? As an engineer, you not only need to know, but also understand. That's why you go down the rabbit hole. That's why you are taught the "unnecessary details". So that you understand and avoid the embarassment of establishing a whole audience around misconceptions and pseudo science, like Mehdi does.

As an example, almost all of the ES & EM theory stuff I learned parrot fashion for my degree I've never needed to use since. That hasn't hindered me in designing satellite communication systems, whether it's the antenna, the feed, the LNA, the PA, the mixers, the oscillators, the filters, the quadrature modulators and demodulators, the modulation and coding schemes, or the firmware implementations.

How do you think people figured out they could have satellite communications systems? Learning field theory like a parrot?

At its extreme, it's perfectly possible in my direct experience to go through an entire electronics engineering degree without ever having picked up a soldering iron or used an oscilloscope.

If you think electronics engineering is all about soldering irons and oscilloscopes, you're not an engineer. Perhaps an electronics technician.

[adx]

My view is that you're doing a disservice to the profession of engineering by unnecessarily teaching details at the expense of more useful and widely applicable practical skills in EE.

Charles Inglis said the following:
'In brief, young people should learn at the university all those parts of electrical engineering which they cannot conveniently learn with us in industry: when they come to us, they should be  able to measure, to use mathematics, and they should be clear about the fundamentals. The rest is not part of the job of the University, and cannot be taught by it in the way that we need.'

So if I leave university without really being able to measure (trusting scope probes and calipers, no idea of thermoelectric potentials), with next to zero workable understanding of mathematics, and mud-like clarity on the fundamentals:

[see below]

...then what do I take to industry? Knowledge that these things exist, and a vague osmotic feel for how it might work, assuming I didn't misunderstand too much?

My problem isn't with the intention, it is with how it is done. The enormous void between what academics believe might be useful, and how it is really used, that universities will not allow to be bridged, no matter how much they say they want to (I have tried, at a high level). I'm not arguing to gloss over or omit fundamentals, but for academic institutions to realise that for almost all their students, it will never, ever be used in that form, if at all. I'd much rather understand something, than trawl through all that arcane notation and hurriedly scrawled diagrams that are 'not to scale'. I'd much rather be exposed to pieces of the truth than a sequence of progressively less dumbed-down lies. I think academics seriously believe that it is is useful, and clearly understood, and above all, real. It's none of those things.

(Edit: Trying to move the attachment inline. More edits: giving up.)

[adx]

Charles Inglis was an academic and during the war, government officer. I don't want to belittle his contribution (or that quoted intention above), but he seems to have been on 'the other side'.

[bsfeechannel]

Which model of mine 'doesn't work' ?? 

You criticized those who demonstrate circuits that can't be modeled. I asked first. What model are you talking about? Perhaps those people are trying to show you that it's your model that is broken. Not their circuits of their demonstrations.

No, they used a scaled-down experiment that is similar but not identical.  And I wish they'd held off until you had actually stated how you expected the circuit to respond so we could compare your results with the pretty much correct results from the heathens using LT-Spice and so on (the stepped reflections). 

Correct my donkey. In LT-Spice, currents flow immediately between the terminals of a capacitor giving a spurious spike before 1 m /c seconds. There is no simultaneity in the universe. This is what Einstein deduced from Maxwell's equations when he formulated his theory of special relativity.

The correct modeling of this problem can only be precisely predicted using the Poynting theorem, which can only be deduced from Maxwell's equations. This is why engineers study these "unecessary" things in their respective degrees.

It's sad, however, that many despise that knowledge and become proud of their ignorance.

With superconducting wires and a lamp that lights at any current level?

Yeah. Just like every single schematic you find on the internet.

Yes, the actual phenomenon would be dry and boring so he spiced it up for the 'general audience'.

What do you have against audience engagement?

[adx]

Charles Inglis was an academic and during the war, government officer. I don't want to belittle his contribution (or that quoted intention above), but he seems to have been on 'the other side'.

That quote comes from Werner von Siemens, not Charles Inglis. Siemens was definitely an industrialist. He also last roamed this Earth in 1892. Science as we know it was new, so the concept of "applied science" was evolving rapidly. Blackboards and mathematics were central to the teaching process.

[bdunham7]

You criticized those who demonstrate circuits that can't be modeled. I asked first. What model are you talking about? Perhaps those people are trying to show you that it's your model that is broken. Not their circuits of their demonstrations.

You lost me somewhere.  I didn't say the circuits couldn't be modelled, they can always be modelled but whether the models are correct or not is another matter.  My criticism was of using physically impossible or experimentally impractical circuits to 'demonstrate' a theory.  You can model those all you like, but you can't test your model in the real universe.  I proposed no specific model for this case, others came up with the transmission line.  I think there is  more to it, as even with no resistance it should also radiate energy into space--so even an ideal transmission line is not a perfect model. But that doesn't affect the outcome of the question posed.

Correct my donkey. In LT-Spice, currents flow immediately between the terminals of a capacitor giving a spurious spike before 1 m /c seconds. There is no simultaneity in the universe. This is what Einstein deduced from Maxwell's equations when he formulated his theory of special relativity.

Numerous people, myself included, have readily observed those shortcomings in the lumped-element approximation of the transmission line and even your cretinous bete noire specifically pointed it out as such.  We all assume that any phenomena is limited to light speed.  Nobody (at least not me) ever thought there would be a faster-than-light spike. By correct, I mean the stepped transitions of indeterminate height, indeterminate because we don't know the impedance of the light bulb.  And I think those better models, which seem to match the experiments, were done using an explicit transmission line not lumped elements.

Relativity is one reason that Derek's proposed correct answer is clearly wrong.  If you accept his impossible magical conditions, an observer at the switch will see the light turn on at about 6.66ns, or twice as long as he says.  An observer at the light will observe both events to be nearly simultaneous.  Only an observer halfway between the two or very far away above or below the plane of the wires will see the approximately 3.33ns transition time.  So (E) None of the above--unless you are in just the right spot.

The correct modeling of this problem can only be precisely predicted using the Poynting theorem, which can only be deduced from Maxwell's equations. This is why engineers study these "unecessary" things in their respective degrees.

OK, then I'm willing to learn.  If you can, specify a reasonably buildable scaled down version of Derek's impossible circuit, using real components.  If you then model it using Poynting's theorem for us, we can then model it in LT Spice and compare the results.  If those results differ significantly, I'll build it experimentally if I can.  I have wire, sawhorses, some old 300-ohm twin lead (I'm not sure how much), scopes that can resolve about 1ns and I'll have to work on a fast edge, long period square wave.  It needs to fit in my garage, or worst case in my backyard, so not too big.

What do you have against audience engagement?

Nothing.  Look at this whole discussion!