Electron Re-arrangement and Flow in Power Lines

[Gerry Rzeppa]

Isn't [Senior Model for Dummies] this just an oxymoron? The Senior model contains a lot of well established maths and empirical evidence (doesn't it?). How can this be for dummies?

If the 613 laws of the Old Testament can be summed up in just two ("Love God, love your neighbor"), and if all of the broad and deep field of ethics can be reduced to seven one-syllable words ("Do what you want done to you"), then surely the gist of Senior Model can be described in a way that is accessible to someone like me. There are scores of interesting and informative "Relativity for Dummies" books and videos; why should this be so different?

Gerry: your model contains just pictures and a main reference that contains very little Maths (iirc).

It's true that my model is essentially a qualitative one (since I'm trying to explain a vacuum tube guitar amp to a ten year old). But it's not true that Chabay and Sherwood are light on the math. Their text is chock-full of stuff like this:

But they're smart enough to remember that statements like that are simply thoughts recorded in another language, a language that can be translated, albeit more verbosely, into plain English. And they understand the importance of this translation from a pedagogical standpoint. Nikola Tesla understood the need for this kind of translation even better: "Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality." Translations for Dummies are reality checks.

What do you actually want out of this exercise?

I'm looking for someone who can give me the gist of the Senior Model, using illustrations and words like Chabay and Sherwood, regarding these three circuits:

And why those three? Because they focus on the points where the Senior Model doesn't make sense to me (and apparently others -- the questions that come to mind are right there in the text.) Chabay and Sherwood resolve these difficulties by talking about surface charges instead of "differential waves," essentially setting the Senior Model aside. Yet intelligent and informed people here insist that the Senior Model is a better, more realistic model. It would help if I could compare apples to apples. I've got the circuits; I've got the Surface Charge model and explanation; what I don't have is the Senior Model explanation at a similar level of abstraction. So I ask again: How might the functioning of these three circuits be described, with the Senior Model in mind, both (a) when the battery is first connected, and (b) after a steady state is reached. What happens in and around the battery, the wires, and the bulb that makes it light up?

 

[nsaspook]

And why those three? Because they focus on the points where the Senior Model doesn't make sense to me (and apparently others -- the questions that come to mind are right there in the text.) Chabay and Sherwood resolve these difficulties by talking about surface charges instead of "differential waves," essentially setting the Senior Model aside. Yet intelligent and informed people here insist that the Senior Model is a better, more realistic model. It would help if I could compare apples to apples. I've got the circuits; I've got the Surface Charge model and explanation; what I don't have is the Senior Model explanation at a similar level of abstraction. So I ask again: How might the functioning of these three circuits be described, with the Senior Model in mind, both (a) when the battery is first connected, and (b) after a steady state is reached. What happens in and around the battery, the wires, and the bulb that makes it light up?

Did you ever think that the reason the other models exist is that they are the simplified abstractions of the 'Senior Model' (it is the whole apple).

It's possible but unnecessary at to field level to completely analyze these three circuits to some mystical level you need to reconcile them all in your head unless you need information about transient effects that are close to zero in human terms at low power levels. Now if you're switching on a main HVDC utility feed instead of a tube amplifier the magnitude of the transient effects on components might warrant a full analysis as the energy levels before steady state are significant. So if you want to understand the 'Senior Model' that many have taken years to build an mental framework about then it's up to you IMO to do the work yourself as I believe in the end your answer will be the only one you accept.

 

[Gerry Rzeppa]

Did you ever think that the reason the other models exist is that they are the simplified abstractions of the 'Senior Model' (it is the whole apple).

Okay, so the Senior Model is to the Junior Model as Einstein's physics is to Newton's. I wonder. The difference, it seems to me, is that Einstein's physics look like an extension of Newton's -- we can delete the terms that don't apply at human speeds and scales and we're back in Newton-land. That doesn't appear to be the case with the Senior Model. As Baluncore put it a few posts back:

"In the junior science model we see a return circuit where a current flows out of one end of the battery, along the wire, down through the load and back through the return wire to the other terminal of the battery. With the senior physics model we see a wave travel from the source towards the load. It travels as a differential wave on the two parallel wires, away from the battery, until it reaches the load. There is no later 'return current path' concept needed."

In the Junior Model we have electrons flowing in the wires around the circuit and back to the source; in the Senior Model we have waves emitted from the source that never return. Surely you can see why I'm having trouble picturing the former as a mere simplification of the latter.

It's possible but unnecessary at to field level to completely analyze these three circuits to some mystical level you need to reconcile them all in your head unless you need information about transient effects that are close to zero in human terms at low power levels. Now if you're switching on a main HVDC utility feed instead of a tube amplifier the magnitude of the transient effects on components might warrant a full analysis as the energy levels before steady state are significant.

That sounds like you're saying the Senior Model isn't very useful when we're dealing with relatively low frequencies and low power levels; is that it? That circuits like the battery-and-bulb and guitar amps are better analyzed and understood in other terms?

 

[Gerry Rzeppa]

Earlier sophiecentaur asked, "What do you actually want out of this exercise?" Perhaps this will help you folks understand what I'm looking for.

Chabay and Sherwood discuss, under the heading "Some Peculiar Circuits," the following:

They then make a modification:

And finally they ask the student to apply what he has learned:

What I'm looking for is a way to analyze circuits like those above qualitatively, so I can get the right answers without doing a lot of math. So I can kind of just "look at the circuit" and "intuitively divine" what will happen. Now the key in this case is the parenthesized comment in the former illustration, obscured by a lot of formulae, that in Loop 3 there is no current because "(no flux enclosed)". With this tidbit in hand, I can look at the above circuits and say, with some degree of confidence, that in (1) only the bottom bulb will light, in (2) they will both light, in (3) only the top bulb will light, and in (4) both bulbs will light. (Boy, I hope I got those right!)

Now all of the current just discussed is obviously induced; the effect on the electrons in the wires is the almost magical result of their interaction with the invisible field emanating from the coil. But I'm pretty sure that if we connected a battery directly to those wires in an appropriate spots, the effects of the solenoid field would be minimal in comparison (unless, of course, the current in the solenoid was unusually strong). Kind of like the way we get hum in a guitar amp if the power transformer is too close to the pre-amp tubes, though the overall operation of the amplifier -- the "through the wires stuff" -- remains essentially the same. So tidbit number two is that a direct connection typically beats an inductive connection, and usually by quite a bit.

Get the idea? I'm looking for (a) a consistent model plus (b) a handful of such "tidbits" that I can pass along to my ten-year-old. And the better I understand the choices, the better I'll be able to pick and choose. So if there are elements of the Senior Model that will help me in this endeavor, please elaborate them. If not, let me know I'm wasting my time and I'll go shopping elsewhere.

 

[anorlunda]

What I'm looking for is a way to analyze circuits like those above qualitatively, so I can get the right answers without doing a lot of math.

I think you are being selfish. You read physics books while skipping the math. Your math phobia is extreme.

The language of physics is math. Why should the advisers and mentors make the extra effort to translate stuff for you when you are unwilling to make the effort to learn the math necessary to study field theory the way other students to?

I think they have been very patient with you. It shows ingratitude if you challenge what they say.

 

[Gerry Rzeppa]

The language of physics is math.

Every language is "a systematic means of communicating by the use of sounds or conventional symbols." English is one, math is another. English is very broad in scope and is accessible to every native speaker; math is narrow in scope though much more precise. I don't need exacting precision to accomplish my ends: if the amp hums, my son and I turn the transformer or move it a little to the left until the hum subsides while I wave my hands around the thing and remind him about the push and pull of his magnets; there's no need to calculate the exact strength, direction, and extent of the field.

I think you are being selfish... Why should the advisers and mentors make the extra effort to translate stuff...

First, because this is where people come for help with physics questions, both qualitative and quantitative. My questions just happen to fall almost exclusively in the qualitative realm and thus require qualitative answers. And secondly because it's a win-win. Translating formulae into words helps not only me, but the experts as well. I know that every time I'm in the expert role and attempt to explain something to a less-developed mind I end up understanding the thing better myself -- and very frequently get insights and ideas that I wouldn't have gotten without that "extra effort." Do I need to quote Einstein here?

 

[nsaspook]

In the Junior Model we have electrons flowing in the wires around the circuit and back to the source; in the Senior Model we have waves emitted from the source that never return. Surely you can see why I'm having trouble picturing the former as a mere simplification of the latter.
That sounds like you're saying the Senior Model isn't very useful when we're dealing with relatively low frequencies and low power levels; is that it? That circuits like the battery-and-bulb and guitar amps are better analyzed and understood in other terms?

Actually I can't see how you are still having trouble after being told the same thing in 10 different electronic circuit web sites across the Internet and yes, in the context of building circuits the battery-and-bulb and guitar amps are usually better analyzed and understood in terms of circuit theory.

 

[Gerry Rzeppa]

...yes, in the context of building circuits the battery-and-bulb and guitar amps are usually better analyzed and understood in terms of circuit theory.

What I'm finding is that both the Senior Model and Circuit Theory are less than ideal for my purposes. The Senior Model for the reasons seen above, and traditional circuit theory because it requires the kid to think one way inside the vacuum tube, and another way outside. At this point, the model espoused by Chabay & Sherwood seems best suited since my son and I can talk about electricity in terms of what the electrons are doing everywhere in the circuit: the readings on his ammeter indicating the flow of electrons through the wires and across the voids in the tubes, the readings on his voltmeter and on the scope reflecting electron surpluses and deficits on the surfaces of the wires and devices. If you re-read my initial and earlier posts in this thread, you'll see that the question I was (and still am) asking is whether my application of Chabay & Sherwood's model to AC circuits (at power-line and audio frequencies) is sound (no pun intended).

Actually I can't see how you are still having trouble after being told the same thing in 10 different electronic circuit web sites across the Internet...

It's a sad fact that no one on any of those "10 different electronic circuit web sites" recommended the Surface Charge Model or the textbook by Chabay & Sherwood to me. I had to find out about those myself, via Google. Hopefully others like myself will stumble on this thread and not have to look so long and hard for the answers they seek.

 

[nsaspook]

What I'm finding is that both the Senior Model and Circuit Theory are less than ideal for my purposes. The Senior Model for the reasons seen above, and traditional circuit theory because it requires the kid to think one way inside the vacuum tube, and another way outside. At this point, the model espoused by Chabay & Sherwood seems best suited since my son and I can talk about electricity in terms of what the electrons are doing everywhere in the circuit: the readings on his ammeter indicating the flow of electrons through the wires and across the voids in the tubes, the readings on his voltmeter and on the scope reflecting electron surpluses and deficits on the surfaces of the wires and devices.

and Bingo, you are back to electrons in electrical science being the focus instead of electrical energy. Completely off the wagon again.

 

[nsaspook]

It's a sad fact that no one on any of those "10 different electronic circuit web sites" recommended the Surface Charge Model or the textbook by Chabay & Sherwood to me. I had to find out about those myself, via Google. Hopefully others like myself will stumble on this thread and not have to look so long and hard for the answers they seek.

Dude, you were talking about this months ago.
http://forum.allaboutcircuits.com/threads/motional-emf-from-an-electron-flow-perspective.113172/page-5#post-882662
and it ended the way most of your thread do.
http://forum.allaboutcircuits.com/threads/motional-emf-from-an-electron-flow-perspective.113172/page-11#post-887074

 

[Gerry Rzeppa]

Let's please get back to my question. This is as far as Chabay & Sherwood take me:

Unfortunately, they don't specifically address variations in surface charge in AC circuits and I thus need to extrapolate. And this is what comes to mind:

The "final steady state" of the circuit isn't so "steady." Since the flow of electrons in the wires is reversing itself many times per second, the surface electrons must also re-arranging themselves continuously, at a similar rate. In other words, it appears that the movement of electrons in a wire carrying alternating current involves both constant re-arrangement and flow of electrons, where the blue surface electrons form, not at the speed of light but in the 60-hertz range, a kind of three-dimensional sine wave in the wire, pushing the pink current electrons back and forth. Like so:

At time 0 we have the wire in equilibrium. The sine wave is at 0, start of a cycle.

At time 1 the blue electrons on the left have made it all the way to the surface, while the blue electrons at the other end of the wire have hardly moved at all. This creates a potential difference that sucks the pink electrons leftward. The sine wave has reached it's positive peak.

At time 2 all the blue electrons have reached the surface. There is no potential difference and the pink electrons have thus stopped moving. The sine wave is again at 0, in the middle of the cycle.

At time 3 the blue electrons on the left have fallen inward while the ones on the right are still on the surface. This creates a potential difference that shoves the pink electrons to the right. The sine wave now reaches it's negative peak.

At time 4 all the blue electrons have fallen back to the initial state, and the pink electrons have again ceased to move. The sine wave is again at 0, ready for the next cycle.

Question: Is that a reasonable extrapolation of the Chabay & Sherwood Surface Charge model?

(And yes, nsaspook, I'm "back to electrons in electrical science being the focus" because I thought we agreed that it isn't helpful to apply the Senior Model in cases like this where the wires are anything but parallel.)

 

[Baluncore]

Question: Is that a reasonable extrapolation of the Chabay & Sherwood Surface Charge model?

It is as reasonable as is your reasoning. You can extrapolate C&S any way you want if it makes you happy.

I don't believe a word of it. Your surface charge model denies the presence of the magnetic fields that accompany all electron motion. If electrons suck each other along then it is because they are mobilised by the presence of a magnetic field outside the wire.

 

[Gerry Rzeppa]

Your surface charge model denies the presence of the magnetic fields that accompany all electron motion. If electrons suck each other along then it is because they are mobilised by the presence of a magnetic field outside the wire.

First of all, it's not my surface charge model. Chabay & Sherwood were inspired by the work of Herman Haertel (his seminal paper can be found here: http://files.eric.ed.gov/fulltext/ED287730.pdf ) and they further developed his ideas into a complete course and textbook for college-level physics students (their reasonings can be found here: http://www.matterandinteractions.org/Content/Articles/circuit.pdf ).

Secondly, nowhere do they deny the existence or the efficacy of either electric or magnetic fields; on the contrary, their text is chock-full of them (and the vectors and formulae that go with them). They do, however, take the position that electromagnetic fields are caused by certain arrangements and movements of electrons, and thus tend to view the subject matter from that perspective. Their pedagogical reasons for eliminating "field lines" from their text can be found in Section IX of their paper here ( http://www.matterandinteractions.org/Content/Articles/AJP-EandM.pdf ).

That electric and magnetic fields are caused by certain arrangements and movements of electrons seems perfectly reasonable to me: scramble the electrons in a magnetized piece of ferrous metal and we find the magnetic field disappears; stop the movement of electrons in a wire and we find the same thing; pair up each and every electron with a proton and the electric field is neutralized.

What makes the subject difficult, of course, is that the very electrons that cause the fields are also affected by the fields. But electrons seem more real (since they can be easily pictured as part of the "matter" category) and are thus easier to describe to a ten-year-old. Electrons in certain arrangements and motions cause fields; but fields -- though they can cause certain arrangements and motions in electrons -- don't cause electrons themselves to exist. J. T. Bell puts it like this:

"Electric fields, magnetic fields, energy, and many other things, are all concepts that we use to explain the observed relationships involving physical objects and their motions. But 'energy' is not a substance in and of itself; it exists only in the context of two or more objects. We cannot observe energy in isolation, or measure it directly. We can only infer the amount of energy involved in any process by measuring the positions and locations of objects before, during, and/or after that process, and performing some calculations. Similarly for electric and magnetic fields. After all, we define the presence of electric and magnetic fields by the observation that certain objects placed in proximity to each other move in ways that cannot be explained by simple contact-type pushes or pulls. I'm not trying to denigrate or belittle these concepts, or suggest that there's any useful replacement for them. They're amazingly useful, and I would not want to try to do physics without them. But we need to keep in mind the dangers of excessive reification of the concepts that we invent to explain what we actually observe. That is, we need to be careful not to ascribe 'too much reality' to them."

 

[Drakkith]

Thread locked for moderation.

 

[berkeman]

Thread will remain closed. Just as back in August, the OP is refusing to listen, and is being argumentative. Thanks everybody for trying.