forgive me -- "sloppy" use of the term "alternating current".

Current 'flow' is not energy, it is a Mechanism for the transfer of energy.

Yes you are quite correct true alternating signals must cross zero.

However as spook points out the effect of interest or importance of a periodically varying direct current (the correct term) may be the same.

On the other hand it may not.

This is manifest in magnetising currents in cores where remanent mangetism builds up if the current is always unidirectional.

Equally a true AC can be extracted by changing the position of the zero line, just as wave energy can be extracted by a mechanism bobbing up and down on the surface of the sea or lake.

 

This is manifest in magnetising currents in cores where remanent mangetism builds up if the current is always unidirencional.

Remanent/ferromagnetism results are primarily quantum mechanical, there is a exchange energy that modifies the quantum spin properties.

 

Hello again, all. I have a different but related question. For the sake of this question, let's let "1 gazillion" equal 6.2*10^18, which makes 1 amp equal to 1 gazillion electrons flowing past a given point in 1 second. Here's the circuit:



The secondary on the transformer has twice as many turns as the primary. Everyone I've asked so far (in private conversation) seems to agree with the figures shown, assuming the transformer is 100% efficient. My question is this:

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?

Thanks!

 

My question is this:

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?

Thanks!

None of the above directly related to electron speed.

 

None of the above directly related to electron speed.

Sorry, but I don't understand. Current is defined as so-many electrons passing a certain point per second -- so speed must enter into it somewhere (eg, if the speed was zero, no electrons would pass the point in question; and all other things being equal, greater speed obviously means more electrons passing the point per second).

Or take this case where all other things are not equal (ie, a fat wire vs a thin wire):

On the top we have lots of balls (electrons) moving slowly, on the bottom fewer balls (electrons) moving four times as fast. Yet both give us an equal number of balls passing the red line per second (current). Surely one of the critical variables in this example is speed, yes?

 

I answered your question "the result of" as a cause and effect. The reduced flow of electrons through the ammeter on the secondary is caused by the load resistance/conductors on the secondary at the secondary voltage. The current (number of electrons) in the primary is caused by that load (calculated by transformer action) in a 100% efficient transformer.

What you say is true in the isolated context of slow electron drift speed at the microscopic view of electricity but a wire is not a space charge device and the ammeter doesn't directly count electron speed, it measures the magnetic field (by various means) generated on it's sensor by the total flow.

~ average drift velocity of electrons in a copper 12 AWG wire
1A: 8.41 cm/hour
2A: 16.83 cm/hour

because they just alternate the net drift electron velocity in that hour is zero, the net movement in one total cycle is zero and the movement in 1/2 cycle is tiny.
So while it's critical in your simple example, for practical circuits the drift speed is so slow while the number of electrons available to flow at the smallest speeds at the required amperage is so huge it becomes an extremely small factor in a circuit.

 

A wire is not a space charge device.

I have been emailing with this person so I ask as Amicus Curiae (friend of the court),
Is a 12AX7 vacuum tube a space charge device?
If it is, please elaborate on electron velocity in a space charge device.
For instance, the suppressor grid in a pentode is said to suppress secondary effects of the electrons hitting the plate at velocity. I suspect that relatively few electrons escape from the cathode and they are all involved in the function of the tube, as opposed to electrons in a solid where the movement occurs in a massive sea of electrons (so the average speed is slower than a snail).

 

I have been emailing with this person so I ask as Amicus Curiae (friend of the court),
Is a 12AX7 vacuum tube a space charge device?
If it is, please elaborate on electron velocity in a space charge device.
For instance, the suppressor grid in a pentode is said to suppress secondary effects of the electrons hitting the plate at velocity. I suspect that relatively few electrons escape from the cathode and they are all involved in the function of the tube, as opposed to electrons in a solid where the movement occurs in a massive sea of electrons (so the average speed is slower than a snail).

All (normal) vacuum tubes operate in space charge conditions where the field accelerates and adds kinetic energy to the particles. The 'space charge' is the effect of those particles to the electric field in vacuum that modifies the distribution of energy of a 'cloud' or beam of those particles that also usually limits the current unless its accounted for. A 12AX7 is a space charge device but its just a regular audio triode tube with no special electron 'cloud' elements like you see in a beam power tetrode or pentode where the electron flow is deflected to a ribbon or sheet to reduce the current limiting effects of space charge.

Space Charge/tube effects:
https://wiki.brown.edu/confluence/download/attachments/29136/Electronic+Tubes.pdf?version=2
https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part9/page1.html
Electron speed in a electric field:
http://farside.ph.utexas.edu/teaching/302l/lectures/node38.html

 

Let me ask you folks a simpler question. A section entitled "The Width of One Coulomb" on ( http://amasci.com/miscon/speed.html ) says, in essence, this:

In copper, one coulomb of movable electrons has a certain size: a cube approximately 0.016 inches across. [In other words] a coulomb in copper is about the size of a grain of salt. And an Ampere is one saltgrain-sized blob moving each second. In 30-gauge wire the saltgrains would be almost undistorted, and so the charges would move at about 0.016 inches/sec.

Now here's a close-up of a 30-guage wire with sky-blue saltgrain-size 1-coulomb globs of electrons (as above) flowing through it:

We have to move one of those globs past the red line, per second, to push one amp of current through that wire. And we have to move two of those globs past the red line, per second, to get two amps of current through that wire. Here's the question:

Do the globs move faster when we're pushing two amps instead of just one?

 

Do the globs move faster when we're pushing two amps instead of just one?

Yes the electron drift velocity is more, but it's not something you would want to do in a real circuit unless you were making a heater. The 'rapid' speed causes even more collisions (resistivity) and the kinetic energy that normally would be in the fields to be transmitted to the load is lost as heat due to those collisions in the wire.

In a wire 'speed kills' electricity so we increase wire size to reduce speed by increasing the conductor cross-section to increase electron density for the same amperage.

 

I think I just landed on a good idea. A coulomb of electrons does not always take up the same amount of length along a wire. Every time you charge a capacitor, you are stuffing more electrons into a confined space with every added volt, therefore, coulombs are compressible. Therefore, velocity is variable.

Good idea? Bad idea?

 

I think I just landed on a good idea. A coulomb of electrons does not always take up the same amount of length along a wire. Every time you charge a capacitor, you are stuffing more electrons into a confined space with every added volt, therefore, coulombs are compressible. Therefore, velocity is variable. Good idea? Bad idea?

So you're picturing this (top 30-guage wire with 1 amp flow, bottom 30-guage wire with 2 amp flow, all electrons moving at the same speed, but with the saltgrain-size globs compressed in the lower wire):


How can that be? The top globs were defined to be exactly as big as necessary to hold a coulomb's worth of electrons -- they can't, by definition, be further compressed.

So how do we get more electrons in a capacitor to charge it up? I would think like this:


Where the white balls represent globs of protons without associated free electrons. We can only fit so many free electrons into a given space in a given material. But every space isn't always full of free electrons. So we can "charge up" that space by filling in the blanks with more electrons, up to the material-defined limit.

 

I don't think so. Free electrons are, by definition, not associated with a proton.

Did you think I was asking you, @Gerry Rzeppa ? I was trying to represent you to the crowd-source of intellect on AAC by phrasing your questions in a way that would be more familiar with this group, and you come up with yet another groundless theory to muddy the water?

Your intense need to defend your ignorance has convinced me to quit wasting my time with you.

Number Twelve

 

First you don't simply stuff more electrons in a space when you 'charge' a parallel-plate capacitor (Capacitors store energy). It takes great force (at the micro-scale) to push many electrons into a isolated plate in space. The net amount of electrons remains the same but you separate charge by having deficit on one side and an excess on the other (sometimes the other side is not a plate but the 'earth' or universe) in a simple circuit. The energy of the capacitor is stored in the electric field from that charge separation. Second the number of free electrons on both conductor plates is astronomical even when compared to the number of free electrons separated to form that electric field.

 

Maybe a better way for you to look at the tube amplifier is to use Passive sign convention for power flows if you want work to be done by charges.

 

Maybe a better way for you to look at the tube amplifier is to use Passive sign convention for power flows if you want work to be done by charges.

Here's my problem. I'm working on a description of the workings of a guitar amp that will be accessible to strongly-right-brained musically-inclined kids. So I need something completely void of all but the simplest math, with an absolute minimum of concepts and terms, and most importantly with an analogy that, while not distorting the facts, is (a) intuitive, (b) concrete, and (c) at a single level of abstraction; in short, something that can be explained almost entirely in pictures.

As I've mentioned before, my inspiration is Ken Amdahl's delightful and informative book, There Are No Electrons: Electronics for Earthlings ( http://www.amazon.com/dp/0962781592 ). My book will be similar, though restricted to a single guitar amp circuit, and with a little less "story" -- but a lot more pictures.

So if you (or anyone here would like to work on that challenging analogy with me), please write me directly ( gerry.rzeppa@pobox.com ). But you'll have to swear off terms like "passive sign convention" and "isolated plate in space" and "electron drift velocity" for the duration, and somehow figure out how to convert the thoughts behind those terms to household words and phrases, easily understood by a 10 year old with an electric guitar in his hands.

 

Here's my problem. I'm working on a description of the workings of a guitar amp that will be accessible to strongly-right-brained musically-inclined kids. So I need something completely void of all but the simplest math, with an absolute minimum of concepts and terms, and most importantly with an analogy that, while not distorting the facts, is (a) intuitive, (b) concrete, and (c) at a single level of abstraction; in short, something that can be explained almost entirely in pictures.

Right-brained (I'm not sure what that really means) doesn't mean stupid. Challenge them with simplified fun facts and you just might be pleasantly surprised at what they are capable of.

 

Right-brained (I'm not sure what that really means) doesn't mean stupid. Challenge them with simplified fun facts and you just might be pleasantly surprised at what they are capable of.

By right-brained (in this context) I mean the kind of person who learns more from a diagram like that on the right, below, than that on the left:


And you're right, they're not stupid; they just speak a different (mental) language. And I'm the translator. But while the picture on the right above is great for getting across a few basic concepts, it's doesn't scale well; I can't describe an entire guitar amp that way. Which is why I'm still searching for just the right analogy and presentation.

 

Most of the musically-inclined people my age somehow managed to complete very technical/engineering schools without the use of cartoons by hard work and study of the needed information.

http://www.livescience.com/39373-left-brain-right-brain-myth.html
https://www.braindecoder.com/neil-d...-debunk-right-left-brain-myth-1120713524.html

 

Can we have some more cartoons by hard work and study please?
He could rival Rockwell.