Electron Flow in a Vacuum Tube Guitar Amplifier

crutschow

Joined Mar 14, 2008
27,231
....................
Is the reduced flow of electrons through the ammeter on the secondary side the result of:

(a) half the number of electrons flowing the same speed as the electrons on the primary side? or
(b) the same number of electrons flowing 1/2 as fast as the electrons on the primary side? or
(c) twice the number of electrons flowing 1/4 as fast as the electrons on the primary side? or
(d) some other ratio?
It's not clear if you every got a straight-forward answer to this question.

The answer is that, for the same size copper wire in the primary and secondary, the electron velocity of the secondary will be 1/2 the primary velocity (although in both cases the velocity is very slow). That obviously is true, since current is charge moved per unit time, thus the secondary has half as many electrons per second going past a give point as the primary, since the number of free electrons per unit volume of copper does not change.
Think of it as water moving in a given size pipe. The number of water molecules past a given point would be directly proportional to the flow rate (velocity).
 

nsaspook

Joined Aug 27, 2009
8,390
It's not clear if you every got a straight-forward answer to this question.
For good reason, his questioning wasn't really about electron drift velocity. It was really about his attempt to make electron speed a factor in the power triangle so the dancing electron mythology could represent energy/power flows.
 

crutschow

Joined Mar 14, 2008
27,231
For good reason, his questioning wasn't really about electron drift velocity. It was really about his attempt to make electron speed a factor in the power triangle so the dancing electron mythology could represent energy/power flows.
How do you know what his question was "really about"?
He had a simple question and the answer is simple. Nothing to do with mythology.
 

nsaspook

Joined Aug 27, 2009
8,390
How do you know what his question was "really about"?
He had a simple question and the answer is simple. Nothing to do with mythology.
I know because a little bird told me. There is more background on this subject than you would know about by just reading this thread.
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
It's not clear if you every got a straight-forward answer to this question. The answer is that, for the same size copper wire in the primary and secondary, the electron velocity of the secondary will be 1/2 the primary velocity (although in both cases the velocity is very slow). That obviously is true, since current is charge moved per unit time, thus the secondary has half as many electrons per second going past a give point as the primary, since the number of free electrons per unit volume of copper does not change. Think of it as water moving in a given size pipe. The number of water molecules past a given point would be directly proportional to the flow rate (velocity).
Excellent! Thank you. Big help. Let me make sure I've got it straight. Here's an image I've got in the right side of my brain:

transformer flow 4.jpg


And here's the corresponding description on the left side of my brain:

1. Since we've got roughly twice as much wire on the secondary side, we've also got twice as many electrons on the secondary side (represented in the drawing by twice as many little balls -- each of which, in reality, is about the size of a grain of salt, and each of which contains about 6.2*10^18 or 1 coulomb's worth of electrons).

2. Now let's say the primary balls are moving fast enough so that two of those balls pass the red mark at the bottom every second. That's 2 amps of electron or current flow. And let's also say that it takes a "pressure" of 120 volts to make those balls move that fast. Then...

3. On the secondary side, we'll see twice as many balls moving through twice as much wire at half the pace set by the primary. 1 ball will pass the line at the bottom every second, and we'll thus get 1 amp of current flow. But we'll also see the "pressure" doubled (to 240 volts) on the secondary side...

And that's where I need help because I want to say why we see double the pressure on the secondary side. I want to say something like, "Because we have to push twice as hard to move twice as many balls." Or, recalling to the student's mind that we're talking AC here, "Because it's hard to get more balls moving, stopping, moving the other way, etc, than fewer balls." Or perhaps, assuming I've introduced a picture of the magnetic field earlier, "Since the magnetic field is acting on twice as many electrons." Or maybe, "The movement of the balls on the secondary side generates it's own magnetic field that conflicts with the primary field." But I've got to say something there to explain the greater pressure. Help!
 

nsaspook

Joined Aug 27, 2009
8,390
Then pardon me for not being clairvoyant. :rolleyes:
I understand but this was completely at the request of the OP to take things off-line so his questions on this thread are not sequential to the questions and answers in total and is a major reason why side PM's should be avoided in a technical thread.
 

crutschow

Joined Mar 14, 2008
27,231
..................... But I've got to say something there to explain the greater pressure.
It's confusing to try to think about the number of electrons when talking about transformer voltage since it is independent of the number of electrons in the wire.
There is a force exerted on each electrons in each winding that is proportional to the time varying magnetic field. So whether it's one electron or a zillion, its the same force.
It's rather like the pressure in a water pipe, which is independent of the amount of water in the pipe.
The total voltage is determined by the magnitude of the field multiplied by the number of turns, regardless of the number of electrons.
Thus twice the turns gives twice the voltage, and that's why we see "double the pressure".
 
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crutschow

Joined Mar 14, 2008
27,231
I understand but this was completely at the request of the OP to take things off-line so his questions on this thread are not sequential to the questions and answers in total and is a major reason why side PM's should be avoided in a technical thread.
Understood.
This confusion is a good reason side PM's should probably be prohibited (or the main thread locked after a PM).
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
It's rather like the pressure in a water pipe, which is independent of the amount of water in the pipe. The total voltage is determined by the magnitude of the field multiplied by the number of turns, regardless of the number of electrons. Thus twice the turns gives twice the voltage, and that's why we see "double the pressure".
So we've got (a) the field, growing and shrinking; and we've got (b) the electrons in the wire moving this way and that as a result. My question is: Why do more turns act as a voltage multiplier? It seems like it must have something to do with how many electrons are affected (moved, energized) by that field. What else could it be?

UPDATE: This site (http://www.sparknotes.com/testprep/books/sat2/physics/chapter16section1.rhtml )
and a number of similar others describe what appears to me to be an analogous situation -- a conducting bar moving across a uniform magnetic field. In every case the field is said to move the electrons in the bar in a particular direction, and that the more electrons that get moved, the greater the induced EMF. They also say that a longer wire (which would obviously expose more electrons to the field, and make more electrons available for movement) can be used to induce a greater EMF. Which makes me think, as above, that the more electrons a field can operate on, the greater the EMF we're going to get. Hence the secondary of our transformer, with twice as much wire (and thus twice as many electrons exposed to the field) ends up with twice as much voltage. Ya think?
 
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studiot

Joined Nov 9, 2007
4,998
Why do more turns act as a voltage multiplier?
After your last brush off I wasn't going to bother addressing issues in this thread again but here is one more try.

Every turn acts independently and all the turns are in series.

It is as simple as that.
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
After your last brush off I wasn't going to bother addressing issues in this thread again but here is one more try.
I'm not sure what you're referring to, but if I've inadvertently offended you, I apologize. If you're referring to my preference for private communications, it's simply because (a) I can use software I'm more familiar with, and (b) I can generally get answers more efficiently (at least 7 of the 12 posts on this page do not even attempt to answer my questions).

Every turn acts independently and all the turns are in series. It is as simple as that.
So kind of like two batteries in series -- we get twice the voltage because there are twice as many electrons ready, willing, and anxious to move around. Yes?
 

crutschow

Joined Mar 14, 2008
27,231
So we've got (a) the field, growing and shrinking; and we've got (b) the electrons in the wire moving this way and that as a result. My question is: Why do more turns act as a voltage multiplier? It seems like it must have something to do with how many electrons are affected (moved, energized) by that field. What else could it be?...............
Sorry, it may seem but that's not true and not what I previously said.

The magnetic field applies the same force to every electron in a loop of wire whether it's one or a zillion. Thus the voltage introduced in each turn is independent of the size of the wire and thus the number of free electrons in a given length of the wire. If it's 30GA wire or 5GA wire, the induced voltage is the same.

Each turn has the same voltage induced so the voltage of each secondary turn adds an equal amount of voltage, making the total voltage proportional to the number of turns..
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
The magnetic field applies the same force to every electron in a loop of wire whether it's one or a zillion.
I get that part. So more electrons must move if there are more to start off with; but they may move with either more, less, or equal effect (due to collisions, etc). I don't know which, but let's not get stuck there.

Thus the voltage introduced in each turn is independent of the size of the wire and thus the number of free electrons in a given length of the wire. If it's 30GA wire or 5GA wire, the induced voltage is the same.
Which must mean that all of the electrons in each loop respond more or less as a "unit" -- perhaps because of the geometry of the thing, or self-inductance, reactance, whatever. (That's why I brought up the analogous case of single wire moved across a magnetic field in my UPDATE above; it seemed a simpler place to start.)

But while we're here, how about a little thought experiment: Let's say our secondary coil had every odd loop made of copper, and every even loop made of a different conductor with half as many free electrons as copper. Will the voltage induced in each turn be equal? Why or why not?

Each turn has the same voltage induced so the voltage of each secondary turn adds an equal amount of voltage, making the total voltage proportional to the number of turns..
I get the "loops in series" part as well. And I can see, if I may speak analogically for a moment, that more words (electrons) don't necessarily make a fatter (higher voltage) book; it's more pages (loops) that make a fatter (higher voltage) book, whether each page (loop) has more words (electrons) or not. That's an advance in my understanding, I think. But there must be limits related to number of words (electrons). A book (transformer) with no words (free electrons) on any page (loop, eg, windings made of cotton strings) isn't really a book (transformer) at all. And, conversely, a book (transformer) with too many words (free electrons) per page (loop) will have a lot of words (electrons) that never get read (moved) since there simply isn't enough time or energy.

My mind is still not at rest on the subject. It would help if I had the answer to the thought experiment I proposed just above: surely the number of free electrons in each coil must have some effect. And I'm pretty sure a transformer made with iron wire (having less free electrons per cubic unit) will not perform as well as one made with copper wire (more free electrons), all other things being equal; I don't know if the voltage would differ, but I suspect it would.

Thanks for your patience.
 

studiot

Joined Nov 9, 2007
4,998
All I see is a dichotomy here.

You say you want to provide a measure uf understanding for the non tecnically minded.

Don't get me wrong I think this is a great idea and that cartoon of yours I plussed is a great way as a teaching aid to stimulate flagging interest in circuit theory rather than the girl in the next desk .

Understanding of what?

Electic Circuit theory

or

The Physics of Electrodynamics

They are quite different subjects.

The electron stream model is not a particularly good one so why introduce electrons at all?

Ohm's law, the power equation, and many more make no more reference to electrons than to little blue martians and have no need of them. That is they might well still be the same if electricity worked by some other means entirely.

In fact, just as the bulk of matter in this universe is hydrogen, which we do not much encounter directly in our lives, so the bulk of electric current is not carried by electrons but by ions.

We happily say that we put 'heat' into a kettle when we boil it or pressure into a tyre when we inflate it, because they are a convenient fictitious model.
Much more convenient that working with the real Physics for ordinary purposes.

So why not do this for electricity?

Especially when you are offering an incorrect view of electric wave motion, in your description of alternating current.

It is one of the planks of wave motion that the wave and its motion is a separate entity from the elements of the medium that carries it and their motion.
In particular the wave goes somewhere but the elements do not.
Alternating voltage is not a stream of particles rushing (or strolling) to and fro.
It is a wave of changing polarity that passes each particle in place as it goes by.
 
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crutschow

Joined Mar 14, 2008
27,231
.......................
My mind is still not at rest on the subject. It would help if I had the answer to the thought experiment I proposed just above: surely the number of free electrons in each coil must have some effect. And I'm pretty sure a transformer made with iron wire (having less free electrons per cubic unit) will not perform as well as one made with copper wire (more free electrons), all other things being equal; I don't know if the voltage would differ, but I suspect it would.
I suggest you put your mind at rest. As I've said for the umpteenth time, the number of electrons has nothing to do with the amount of voltage introduced. You seem to be fixated on this incorrect view and I seem unable to dissuade you from that. :confused: Using different words to say the same thing doesn't change that.

Certainly a transformer with iron windings will have a much higher resistance and thus have a higher voltage drop for a given output load, but the open-circuit output voltage is identical to one with copper wires of the same number of turns.

Look at the transformer equations. There's nothing in them about the number of electrons, and introducing that into a discussion of transformers for students will only confuse them, not enlighten them as you seem to think.
I went through 4 years of electrical engineer schooling and electrons were never once mentioned in conjunction with transformers.

I worry about your students. :rolleyes:
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
You say you want to provide a measure uf understanding for the non tecnically minded... Understanding of what? Electic Circuit theory or The Physics of Electrodynamics?"
A little of both, I think. I want to start with free electrons in the atoms of conductors (using the atom model with the different electron shells) and end up with a working guitar amp. With as few auxiliary concepts in between as possible.

The electron stream model is not a particularly good one so why introduce electrons at all?
Because the key element in a guitar amp is the vacuum tube. And the operation of a vacuum tube is invariably described with electrons boiling off a heated cathode and rushing across a void, slamming into a plate, and... and that's where this simple, concrete, easy-to-understand description typically ends. I want to complete it (in those same simple, concrete, easy-to-understand terms).

...you are offering an incorrect view of electric wave motion, in your description of alternating current... It is one of the planks of wave motion that the wave and its motion is a separate entity from the elements of the medium that carries it and their motion. In particular the wave goes somewhere but the elements do not.
It seems I'm more a "particle" man than a "wave" man. I find the particle-oriented view of atoms, light, etc, easier to understand than the wave-oriented view. And since, as above, vacuum tubes are invariably described as "particle" devices, and since an amp of current is defined as 6.2*10^18 "particles" of electricity (electrons) moving past a point in one second (in copper, about one salt-grained-sized blob per second -- see how tangible and accessible that is?), it doesn't seem (to me) an unreasonable thing to attempt.
 

Thread Starter

Gerry Rzeppa

Joined Jun 17, 2015
170
Certainly a transformer with iron windings will have a much higher resistance...
Why? Because iron is not as good a conductor as copper. Why? Because copper has more free electrons per cubic unit of material. And I'm back to electrons.

Look at the transformer equations. There's nothing in them about the number of electrons
Let's take that simpler case of a conducting rod being dragged across a uniform magnetic field. What happens is invariably described as free electrons moving toward one end of the rod as the field applies force to them. And this imbalance in the location of the free electrons is the essence of the induced EMF. In other words, it seems to me that "the bottom line" is that we have magnetic fields causing free electrons to move -- the rest is effect, not cause. I'm trying to stick with the causes (as above with why iron windings don't perform like copper ones). But bear with me.

The formula usually associated with this rod-moving-across-a-uniform-magnetic-field experiment says the length of the rod is a determining factor in the magnitude of the induced EMF. Why? I'd like to answer that question in the same terms as those used to describe the original effect (ie, the movement of electrons toward one end of the rod). It appears to be a rank-and-file (row and column) problem. It doesn't seem to matter how many "columns" of electrons one has in his rod, but it does matter how many "rows"; ie, a wider rod will not effect the induced EMF, but a longer one will. I don't know how to explain why this is so without referring to the arrangement of the electrons in the rod.

I went through 4 years of electrical engineer schooling and electrons were never once mentioned in conjunction with transformers.
Academia is infamous for conveying to the student the WHATs and HOWs of things without imparting an understanding of the WHYs. It's that "why gap" I'm trying to fill.
 

studiot

Joined Nov 9, 2007
4,998
And therein lies your problem.

You are taking an inappropriate theory in physics and trying to force it onto circuit theory in electronic engineering.

There are no atoms in conductors or semiconductors, only giant molecules connected by metallic bonding.
This is why they work.

No the definition of alternating current is not a particular number of electrons rushing past a particular point in a particular time.
And within conductors and semiconductors no electrons are rushing anywhere.
In fact if you took that model to the extreme you would have to explain why the electrons in a vacuum tube are not rushing back to the cathode every half cycle.

Your physics is untenable and you are not listening to those who offered help.

But why worry, I still think it counterproductive to work in terms of some assumed physics model unless you have to.

Ordinary electric circuit theory is much easier to carry out and understand

because it was designed for that express purpose.
 
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