Understanding the Nature of Electricity: Flow of Electrons or Electric Charge?

[toneboy1]

I've always been given conflicting messages like that we only use conventional current because they were confused years and years ago. Anyway I'm wondering if 'electricity' is the flow of electrons or "electric charge" like I heard once, I assume they meant like a flow of empty valency shell holes.

Any thoughts as to which it is?


Thanks again!

 

[jambaugh]

It is the flow of electric charge. However this is typically the flow of electrons. The flow of empty valence shell holes in one direction corresponds to the flow of electrons (each filling the prior hole) in the opposite direction. It is just two ways of describing the same thing.

But if you have say, a radioactive source emitting alpha particles (helium nuclei with charge +2e) then this flow of particles is also an electric current.

 

[toneboy1]

Right, I see, so if you were to apply that to a battery in slow motion and super-vision and just to focus on the empty holes, would they move out of the positive terminal through the wire, through the circuit back into the negative terminal?

Cheers.

 

[Averagesupernova]

I don't think you have what people refer to as hole flow in conductors. Just semiconductors.

 

[toneboy1]

I don't think you have what people refer to as hole flow in conductors. Just semiconductors.

There must be, otherwise the shell of the conducting atoms would fill up.

 

[Bassalisk]

Electricity is not flow of electric charge. What we think of electricity is a impulse of energy. Yes electrons do move, but very very very slow. Like a half a centimeter a second. But they bump into each other and create this impulse, like a wave which travels with speed of roughly half speed of light. (depending of which material are we talking about)

 

[RJK]

I've often wondered just how far the electrons (or electric charge) travel per unit of time. Not as fast as light, right. But if the power generating station is say 100 miles away, would one power cycle (60Hz) or 17mSec travel to my homes and back to the generator?

 

[jambaugh]

I've often wondered just how far the electrons (or electric charge) travel per unit of time. Not as fast as light, right. But if the power generating station is say 100 miles away, would one power cycle (60Hz) or 17mSec travel to my homes and back to the generator?

As I recall, the actual electron drift speeds are suprisingly slow...(googling)... Here's a figure from http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ohmmic.html"

Drift speed of 4.3mm per second.

 

[RJK]

4.3mm/sec? But when I flip on a light switch 100 yards away it comes on immediatly. Something isn't right with that.

 

[jambaugh]

4.3mm/sec? But when I flip on a light switch 100 yards away it comes on immediatly. Something isn't right with that.

What travels at near speed c, is the voltage which is the electromagnetic interaction between the electrons. Voltage = electromagnetic interaction which propagates at speed c. Note the electrons do vibrate around thermally at substantially faster than 4.3mm/sec.

Here's a partial analogue. If you turn on or off a faucet, the drop/jump in pressure along the pipe propagates at the speed of sound in water even though the actual flow rate of the water is much less than that speed... and a good thing to or you'd be cut to ribbons taking a shower

 

[Bassalisk]

Like jam said, they do move, but in that process of moving they bump into each other, because they are tightly packed. That bumping is also form of movement. And that movement propagates at the speed, roughly half the speed of light. (Why half? Material reasons)

If you really want to understand this movement, you will have to uptake solid state chemistry etc, thermal movement, drift speed, thermal speed etc.

http://phet.colorado.edu/en/simulation/signal-circuit

In this circuit you will see this bumping, if you watch carefully.

I repeat, current is NOT movement of electric charges, this is common misunderstanding. Current is a impulse of energy. And even that last one cannot be taken for granted.

Life sworn physicists deny even the concept of current. They say that only electric potential exists. Everything else is derived.

 

[I_am_learning]

I would like to put up my views. Electricity is invisible liquid that flows in wire/ Electricity is flow of electrons/Electricity is flow of charge/Actually elctrons flow // etc etc are all theories.
First decide which phenomenum you want to study, the choose thories. Theories are just means of explaining out things. There is not any theory that provides the 'actual fact' for it don't exist. However, there is a general trends that newer theory are supersets of older theory's so explain more things. So we are led to believe that the most recent theory explains the actual thing.
For example, its not that bad to assume that the sun revolves round the Earth and design a solar panel that faces the sun. You don't need to know that its actually the Earth that revolves round the sun. However, if you want to make a solar system voyager, then you may even need to consider that the Earth don't rvolve round the sun in nice circle.

So, in nutsell, my view is that: Don't run after theories, for there is no ultimate theory. Choose just the sufficient theory that explains the phenomenum of your corncern.

 

[Bassalisk]

I would like to put up my views. Electricity is invisible liquid that flows in wire/ Electricity is flow of electrons/Electricity is flow of charge/Actually elctrons flow // etc etc are all theories.
First decide which phenomenum you want to study, the choose thories. Theories are just means of explaining out things. There is not any theory that provides the 'actual fact' for it don't exist. However, there is a general trends that newer theory are supersets of older theory's so explain more things. So we are led to believe that the most recent theory explains the actual thing.
For example, its not that bad to assume that the sun revolves round the Earth and design a solar panel that faces the sun. You don't need to know that its actually the Earth that revolves round the sun. However, if you want to make a solar system voyager, then you may even need to consider that the Earth don't rvolve round the sun in nice circle.

So, in nutsell, my view is that: Don't run after theories, for there is no ultimate theory. Choose just the sufficient theory that explains the phenomenum of your corncern.

I believe I know what are you talking about. But that only goes to the level when you are solving problems.
And I think you are wrong when you say that theories don't explain things. Explaining really goes down how much vocabulary you have to describe a certain event.

Classical physics was fine and dandy until you went to molecular level, and still quantum physics is made in such way that it applies to macroscopic ways too. How do you think people felt when Schrodinger derived almost all quantum laws from his equation?

Leibniz and Newton came to the same formula. One from physics one from mathematics. All things are connected. So theories do explain a lot of things. But some theories are not meant to explain, but rather to help in some problems.

Take an example of Maxwell's contour currents. He developed an system of equations to easily solve some complex circuits. But in a real theory, there is no such thing as contour current.

I believe that this fellow is asking what is happening when u put a light bulb connected with wires to the battery terminal. Why does it light up? Of course there is a explanation that is reasonable and correct.

Quantum physics, solid state can verify this easily. But right now we are trying to give some RIGHT directions, so a guy can go on his own and explore the concept.

Of course you cannot explain current and electricity in one forum thread. People spend their whole lives just studying that.
And like I said in one forum thread before, conventional way of current is used because Franklin put it that way. Why it didn't change? Because it would took too much effort and you would get not so much of a result. They didn't know back then what is going down on the microscopic level. He chose from + to - for the same reasons people chose left to be left and right to be right. There is no special reason for it, just you have to set some things. Later when other electronic elements where made, there was no conflict with it so, things stood like they are today.

 

[sophiecentaur]

I would like to put up my views. Electricity is invisible liquid that flows in wire/ Electricity is flow of electrons/Electricity is flow of charge/Actually elctrons flow // etc etc are all theories.
First decide which phenomenum you want to study, the choose thories. Theories are just means of explaining out things. There is not any theory that provides the 'actual fact' for it don't exist. However, there is a general trends that newer theory are supersets of older theory's so explain more things. So we are led to believe that the most recent theory explains the actual thing.
For example, its not that bad to assume that the sun revolves round the Earth and design a solar panel that faces the sun. You don't need to know that its actually the Earth that revolves round the sun. However, if you want to make a solar system voyager, then you may even need to consider that the Earth don't rvolve round the sun in nice circle.

So, in nutsell, my view is that: Don't run after theories, for there is no ultimate theory. Choose just the sufficient theory that explains the phenomenum of your corncern.

There are good theories and there are poor theories. A good theory doesn't only explain your chosen phenomenon. it can accurately predict what will happen in brand new situations. Unless you can come up with a theory that explains significantly more than the conventional theories for 'electricity' then stick with them. They work well enough to make this computer talk to your computer, wherever you happen to be.

Only an eejit would call any theory an "ultimate" theory. But,also, no one but an eejit would say that all 'old' theories are wrong. They just have a limited scope.

 

[sophiecentaur]

btw, does this "invisible liquid" also flow across the plates of a Capacitor, through air or an insulator?

 

[I_am_learning]

I am sorry if I tried to mess up the learning process of the OP. But, I simply wanted to warn him about what theories really are. You guys of course have told much better than me on that subject.

 

[jambaugh]

...I repeat, current is NOT movement of electric charges, this is common misunderstanding. Current is a impulse of energy. And even that last one cannot be taken for granted.

Life sworn physicists deny even the concept of current. They say that only electric potential exists. Everything else is derived.

I take some exception to these statements. Current IS movement of electric charge BY DEFINITION. Signals on the other hand...

On the other, I don't know to which physicists you've been listening. Electric potential is a convention we can implement since electrical forces are conservative. Electromagnetic Force (the E and B fields) are what exist as they are empirically observable (by virtue of their effect on a test charge). Likewise charge is observable and thence too changes in charge and hence flow of charge a. k. a. currents. The physicist qua physicist believes in the empirical and understands theoretical constructs as speculation.

 

[Bassalisk]

I take some exception to these statements. Current IS movement of electric charge BY DEFINITION. Signals on the other hand...

On the other, I don't know to which physicists you've been listening. Electric potential is a convention we can implement since electrical forces are conservative. Electromagnetic Force (the E and B fields) are what exist as they are empirically observable (by virtue of their effect on a test charge). Likewise charge is observable and thence too changes in charge and hence flow of charge a. k. a. currents. The physicist qua physicist believes in the empirical and understands theoretical constructs as speculation.

I strongly disagree with definition that current is MOVEMENT of electric charge. This is wrong, in my opinion, on some very important levels. Current is, for me impulse of energy. It is in some cases movement of charge, but in general theory where circuit is analysed, its not.

If that is definition, that means that charges in the wires move at speeds near speed of light, which we all know don't. They move very slow at drift velocity. Further this would mean that the wire would get super hot in very short time.
Current is a wave, similar to electromagnetic wave that propagates through medium.

 

[Studiot]

I strongly disagree with definition that current is MOVEMENT of electric charge. This is wrong, in my opinion, on some very important levels. Current is, for me impulse of energy. It is in some cases movement of charge, but in general theory where circuit is analysed, its not.

Perhaps if you had grown up in the age of vacuum tubes you would have had a different view?

 

[Bassalisk]

Perhaps if you had grown up in the age of vacuum tubes you would have had a different view?

What's your point mate?

 

[Studiot]

The anode current is a stream of electrons moving through space.
Exactly what you have rejected as a a current.

 

[Bassalisk]

The anode current is a stream of electrons moving through space.
Exactly what you have rejected as a a current.

Maybe definition and formulas say that current is charge/time, but here at my university, if you say that current is directional flow of charge you would be corrected. And I think i know what are you talking about.

It is in some cases movement of charge, but in general theory where circuit is analysed, its not.

Read my statements carefully.

Then we have to distinct what are we talking about, current in wire.

 

[Studiot]

Are you (and your university) denying that is how a vacuum tube (including old fashioned computer monitors so it was not so very long ago) works?

Why should this thread be limited to current in wire?

the title is 'What is electricity, exactly?'

 

[Bassalisk]

Are you (and your university) denying that is how a vacuum tube (including old fashioned computer monitors so it was not so very long ago) works?

Why should this thread be limited to current in wire?

the title is 'What is electricity, exactly?'

Then well, I wandered off the subject, because i mainly study circuits. I deal with resistors and electronic elements and not vacuum tube. Electricity, for my needs, is what I said. Maybe in general physics is defined like you said.

I've always been given conflicting messages like that we only use conventional current because they were confused years and years ago.

He mentioned conventional current, so I figured he was talking about circuits.

 

[Studiot]

Don't forget, this is an electric universe.

The theory of man made circuits is one very small corner of electricity which runs everything from our minds and bodies to chemical reactions to planetary magnetism to...

 

[sophiecentaur]

. . . . This is wrong, in my opinion, on some very important levels. Current is, for me impulse of energy. It is in some cases movement of charge, but in general theory where circuit is analysed, its not.
. . . . . .

You need to be very careful when you make statements like that. The units of Current and energy are quite different so they just cannot be the same thing. If you are trying to tell people 'the way things are' then you must obey the basic rules! Current is the time differential of Charge - by definition. That charge may not be yer actual particles but it's still charge.

 

[Bassalisk]

You need to be very careful when you make statements like that. The units of Current and energy are quite different so they just cannot be the same thing. If you are trying to tell people 'the way things are' then you must obey the basic rules! Current is the time differential of Charge - by definition. That charge may not be yer actual particles but it's still charge.

If we are still talking about circuits, then I disagree. I will continue this discussion tomorrow.

 

[sophiecentaur]

I really don't think that you are in any position to argue with dimensional analysis. You would need to invent a whole new Science if you wanted to do that. The point is that Current and Energy exist as concepts inside and outside of circuit theory and you just have to be consistent about that.

 

[Bassalisk]

I really don't think that you are in any position to argue with dimensional analysis. You would need to invent a whole new Science if you wanted to do that. The point is that Current and Energy exist as concepts inside and outside of circuit theory and you just have to be consistent about that.

Ok if you say so.

 

[f95toli]

Maybe definition and formulas say that current is charge/time, but here at my university, if you say that current is directional flow of charge you would be corrected. And I think i know what are you talking about.

It is likely that one of the changes that will be made to the SI within the next few years is that the Ampere will be defined by fixing the value of e; this means that the base unit Ampere will be realized by counting the number of charges that passes through a circuit in a second. Hence, the Ampere (and therefore arguably current) will be defined to be flow of charge.

Note that there are already current generators out there that generate a current by pumping electrons one-by-one. The main problem with the ones we have is that the current they can generate is to small (pA) but that is a problem that will hopefully be solved.

 

[sophiecentaur]

Ok if you say so.

It's not just I who says so!

 

[Bassalisk]

It is likely that one of the changes that will be made to the SI within the next few years is that the Ampere will be defined by fixing the value of e; this means that the base unit Ampere will be realized by counting the number of charges that passes through a circuit in a second. Hence, the Ampere (and therefore arguably current) will be defined to be flow of charge.

Note that there are already current generators out there that generate a current by pumping electrons one-by-one. The main problem with the ones we have is that the current they can generate is to small (pA) but that is a problem that will hopefully be solved.

My whole point here is: IF the current is defined as the directional flow of charge(in a wire), then by calculations and given parameters you would find that propagation of current is very slow, which we all know isn't.

 

[Studiot]

As to the question of what is electricity I commend the introductory chapter of Professor Hammond's book where he addresses exactly this question on pages 12 - 13.
He provides several explanations one of which is intriguingly

Every student of electricity is likely to be asked by his friends to explain what electricity is....

..."I do not know"
This will also be true and often gives a pleasing sensation to the questioner.

 

[sophiecentaur]

Current is the Time derivative of Charge. NOT the speed of charge carriers. Do you not see the difference? This is so basic.

 

[Bassalisk]

Current is the Time derivative of Charge. NOT the speed of charge carriers. Do you not see the difference? This is so basic.

Ok i rest my case.

 

[sophiecentaur]

Which one?

 

[Bassalisk]

Everything.

 

[sophiecentaur]

Everything.

Meaning that the "propagation of current" (whatever that means) is very fast? But we know the charge carriers in a metal move verrry slowly but in a CRT they go very fast. Perhaps you mean the Energy is transferred very fast. Yes - quite near the speed of light.
You could, at least, try to use the right terms if you want to change the course of Physics.

 

[Bassalisk]

Well yes, when u put it that way.

 

[toneboy1]

This was a great thread.

 

[sophiecentaur]

Well yes, when u put it that way.

 

[DragonPetter]

I strongly disagree with definition that current is MOVEMENT of electric charge. This is wrong, in my opinion, on some very important levels. Current is, for me impulse of energy. It is in some cases movement of charge, but in general theory where circuit is analysed, its not.

If that is definition, that means that charges in the wires move at speeds near speed of light, which we all know don't. They move very slow at drift velocity. Further this would mean that the wire would get super hot in very short time.
Current is a wave, similar to electromagnetic wave that propagates through medium.

Current can be defined as actual charge carrier flow. I think the mix up is thinking of flow rate as speed (displacement rate) - they are not the same thing. Is it safe to say current flow is more similar to a flux concept than a displacement concept? If you look at a certain cross section, current is the number of charge passing through that surface at a given time. You can have a lot of charge move really slowly (and so displace very little distance), and it will still be a high current because the number of charges is so high.

 

[sophiecentaur]

Just consider a CRT circuit. The same number of electrons per second going all the way round. The ones in the wires going at snail's pace and the ones in the tube going at a speed not much lower than c. Flux not speed.

 

[Kholdstare]

Its flow of electric charge.

 

[sophiecentaur]

Its flow of electric charge.

Nothing wrong with that but the term flux gets further away from the implication of speed which we need to avoid, perhaps.

 

[toneboy1]

Nothing wrong with that but the term flux gets further away from the implication of speed which we need to avoid, perhaps.

h'mm, ok that confuses me a bit, we agreed that I = time derivative of charge = charge/time
(I think)

So as the electrons are drifting IN THE WIRE quite slowly SOMETHING is moving near the 'speed' c depending on material. But we also said that current = flow of electric charge ??

*EDIT*
could we model the flow of charge like a sound wave, electrons pushing on each other but not really moving position?

 

[sophiecentaur]

Better. Whatever the 'amount' of current, the signal / energy / wave gets there at the same speed.

 

[Kholdstare]

Nothing wrong with that but the term flux gets further away from the implication of speed which we need to avoid, perhaps.

Well, basically flow of charge is what defines current. However, one can draw a relationship between drift velocity and current. I = q x n x A x vd. But saying that the current is all about speed and nothing else is false. The (average) speed of electron multiplied by electron concentration per unit length (nA) gives the number of electron passing a particular point (actually area) of the conductor per unit time.

 

[toneboy1]

Well, basically flow of charge is what defines current. However, one can draw a relationship between drift velocity and current. I = q x n x A x vd. But saying that the current is all about speed and nothing else is false. The (average) speed of electron multiplied by electron concentration per unit length (nA) gives the number of electron passing a particular point (actually area) of the conductor per unit time.

That seems completely different to:

Current is the Time derivative of Charge. NOT the speed of charge carriers. Do you not see the difference? This is so basic.

I'm sure Bassalisk would have a fit...

 

[DragonPetter]

That seems completely different to:
I'm sure Bassalisk would have a fit...

They are not different, only different levels of describing the same concept. Kholdstare is explaining the physical description of how it comes about which shows that you can derive the flux (what the definition of current flow hinges upon) as being dependent on the charge drift velocity. Because something is dependent on a variable does not make that variable the definition of what that something is - there are other factors in the context, being q, n, and A, that allows the inclusion of drift velocity to derive current flow.