Electric charge flow in AC and DC

AI Thread Summary
Energy transmission in both AC and DC circuits occurs through the electromagnetic field, not merely through electron flow. While DC can be likened to a continuous flow, and AC involves alternating directions, the analogy of electrons as ants or water waves is misleading. Electrons exhibit random thermal motion, with a superimposed drift in DC and alternating drift in AC. The concept of conventional current, where current is modeled as positive charge flow, predates the discovery of electrons and helps simplify circuit analysis. Understanding electricity fundamentally involves recognizing the role of the electromagnetic field rather than focusing solely on electron behavior.
Nihad Nazmul
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Can I say that energy transmitted in DC by electrons flow like ants walking align and in AC by electron vibration like water wave ?
 
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No, because it isn't true. In both AC and DC the energy is transferred through the electromagnetic field. Current flow in a DC circuit is vaguely like ants marching in a line, but even that technically isn't accurate.

Try the following article. It's a little advanced, so don't worry if some of it doesn't make a lot of sense.
http://www2.warwick.ac.uk/fac/sci/physics/current/teach/module_home/px263/lectures/sefton.pdf
 
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From my understanding Direct current and alternating current only flow differently. The protons neutrons and electrons are in the same order. Direct-current is a continuous flow. Alternating current alternates from positive to negative.
 
Electrons wiz about in random directions due to them having thermal energy.
In a DC circuit there is a drift super imposed on this random motion.
In an AC circuit the super imposed drift is first one way then the other.

If I remember correctly..
Typical thermal velocity is order 105m/S
Typical drift velocity is order 10-5 m/S

It might be a surprise that electrons take a long time to drift any significant distance. It's order cm per hour depending on the current.
 
Nihad Nazmul said:
Can I say that energy transmitted in DC by electrons flow like ants walking align and in AC by electron vibration like water wave ?
Pictorial models of something as complicated as Electricity will just manage to confuse you. There is no short cut to understanding Electricity. One thing I can tell you is that using electrons when you want to describe what goes on in circuits is worse than unnecessary. Going back a few decades, schools taught electricity without introducing electrons (despite the fact that it was know how they are 'involved'; that is night here nor there.) We had no trouble in our electrical learning. Most of the electrical devices that you use were designed without using 'electrons' in the analysis. That goes for generators, radio antennas and motors, to name but three)
 
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I agree. About the only time you need worry what the electrons are doing is when you are trying to understand the inner workings of semiconductors. You don't usually need worry about that stuff to actually use them.
 
I just can't understand how anyone can be telling the OP (and millions of others) information that results with the words in that post. It isn't his/her fault - it just makes life harder for students these days when they have to undo such ideas for themselves.
 
Drakkith said:
In both AC and DC the energy is transferred through the electromagnetic field.

Thank you. I think now I have a clear view of electricity. Let's set a conclusion,
1. Electric current is caused for potential difference.
2.Potential difference push electric field and electric field pile up the electrons.
3. As electron in motion it proceed magnetic field.
4. The energy transfers via electromagnetic field, specifically it is photon . As photon provide the convulse to electrons speed remains about 0.8c-0.9c and electrons gain drift velocity.
But I couldn't specify one thing that why electrons and current ( flow of electromagnetic field) flow inverse ? Perhaps I've got a reason . That direction of electric field and its push that means force is inverse, the equation F=(-e)E is the precision.
Are my decisions right? Please confirm me .
 
No, it looks like you've gotten everything mixed up and I don't even know where to begin to help you. Any ideas, Sophiecentaur?

Edit: I'm having a little trouble understanding you, so you may have a few things correct but just didn't word them correctly.
 
  • #10
Okay, let's conclude individually . My first decision is 'Electric current is caused for potential difference' . As electric field is involved with Potential difference I think I can tell that . There is also an equation, V=Ed . At first confirm this?
 
  • #11
Do you mean, 'caused by a potential difference'?
 
  • #12
Yes.
 
  • #13
Okay, then yes, current flow is caused by applying a voltage (potential difference).
 
  • #14
Now,second one." Potential difference push electric field and electric field pile up the electrons" . I said that because there is an equation, F=(-e)*[V/d] . I've got the decision as a answer of this question "Why electric field will pile up the electrons ? " . Isn't it the real deal?
 
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  • #15
The potential difference is the result of an electric field, not the other way around. The electrons 'pile up' due to this electric field. Note that potential difference is measured in units of electric potential, which is defined as: the amount of electric potential energy that a unitary point electric charge would have if located at any point of space, and is equal to the work done by an electric field in carrying a unit positive charge from infinity to that point. (Full article here: http://en.wikipedia.org/wiki/Electric_potential)

This just means that voltage, also known as potential difference, is a measure of the potential energy of a charge between two points in an applied electric field. This could be anything from a single particle in a vacuum under the influence of an electric field, to a complicated circuit with multiple power supplies and loads.
 
  • #16
So electric field pile up the electrons by electric force[ E=F/(-e) ]. Third decision was " As electron in motion it proceed magnetic field ". This one maybe right, because without motion magnetic field can't manifest itself. But , it also may true that without electron only for motion of electric field magnetic field can be revealed.
 
  • #17
If by that you mean that a moving charge creates a magnetic field, yes. I thought you meant that 'an electron in motion is preceded by a magnetic field', which doesn't make any sense.
 
  • #18
I exactly meant that . Now, last one " The energy transfers via electromagnetic field, specifically it is photon . As photon provide the convulse to electrons speed remains about 0.8c-0.9c and electrons gain drift velocity." I've already tried to clear this one . What do you say?
 
  • #19
I'd forget you ever heard the word 'photon' for now. It's only going to confuse you. It is utterly unnecessary to understanding energy transfer in electronic circuits and the actual theory of mediating particles is so complicated that you don't have a chance of understanding it in any detail at this time. (Heck, neither do I) Energy transfer in electronic circuits is easily covered by classical electromagnetic theory.
 
  • #20
I will never ever use the word "photon" rather electromagnetic field. Okay, now come to my problem "I couldn't specify one thing that why electrons and current ( flow of electromagnetic field) flow inverse ? Perhaps I've got a reason . That direction of electric field and its push that means force is inverse, the equation F=(-e)E is the precision. " There may have more reason for this .
 
  • #21
In an AC circuit, the current flows in alternating directions because the polarity of the voltage alternates as well. That's it.

Also, just to be clear, the flow of current is not the same thing as the transfer of energy via an EM field. The EM field doesn't even flow.
 
  • #22
Then what means by flow of current? Flow of charge per time?
 
  • #23
Yes! That is exactly what amperage (the unit of current) is measuring! The number of charges flowing past a point per second.
 
  • #24
Okay. Which charge flow Is the current? Answer is electron . Then why it is reverse electron ?
 
  • #25
I don't understand what you mean by 'reverse electron'.
 
  • #26
Direction of current flow is reverse to the direction of electron's flow .
 
  • #27
Are you talking about what is known as 'conventional current' where current flow is envisioned as positive charges flowing?
 
  • #28
Drakkith said:
Are you talking about what is known as 'conventional current' where current flow is envisioned as positive charges flowing?
Yes.
 
  • #29
It turns out that modeling current as positive charges gives you the exact same predictions as using negative charges, provided that the direction of current flow is opposite in each case. Prior to the discovery of the electron, current was modeled as positive charges flowing through a circuit. It's stuck around since then.
 
  • #30
I knew these before . But what is the role of electromagnetic field?
 
  • #31
What do you mean?
 
  • #32
Maybe I messed up energy and current together. Now I have the conclusion. Glowing a light bulb current has no role and it is done by electromagnetic magnetic field .
 
  • #33
Nihad Nazmul said:
Maybe I messed up energy and current together. Now I have the conclusion. Glowing a light bulb current has no role and it is done by electromagnetic magnetic field .

As with most things, it isn't quite that simple and I'm afraid that we've reached the limit of my knowledge in this area. Just consider that power, which is energy transferred over time, can be find by: P=VI, where P is power, V is voltage, and I is current. In other words, the amount of energy transferred over time is equal to the product of the voltage times the current flow. So I'm not sure I'd say that current has no role in causing a light bulb to glow.

I hope I haven't managed to lead you astray. Perhaps someone with more knowledge than myself can take over from here.
 
  • #34
Nihad Nazmul said:
Maybe I messed up energy and current together. Now I have the conclusion. Glowing a light bulb current has no role and it is done by electromagnetic magnetic field .

The filament heats up because electrons collide with metal ions. So the current is important.
 
  • #35
Electromagnetic field transmits energy. As electromagnetic field acts in quanta that means photon. Then glowing up of bulb filament easily can be explained. Filament produce radiation when photon collide with electron (in filament orbital) and electron completes the Bohr's quantum jump . In glowing the bulb maybe current doesn't interfere . But electromagnetic field depends on current that means flow of electron. So, the more electron the more work therefore the more energy.Note that I may have mistakes.
 
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  • #36
Nihad Nazmul said:
I will never ever use the word "photon" rather electromagnetic field. Okay, now come to my problem "I couldn't specify one thing that why electrons and current ( flow of electromagnetic field) flow inverse ? Perhaps I've got a reason . That direction of electric field and its push that means force is inverse, the equation F=(-e)E is the precision. " There may have more reason for this .
This is a problem that many people have but it is not a real problem. The Conventional Current was a concept which was used long before anyone had an idea of the existence of electrons. Electric current was just some quantity - a substance, of a sort, that could (and still can) be treated as a fluid that flows according to Potential difference ('downhill'). Someone chose a Sign for the connections on a standard battery (or on a piece of insulator that had been rubbed with something) and that choice was adopted universally and classical electromagnetic theory was developed using this convention. It is all perfectly consistent, with Current flowing from + to -. A long time later, the particle that conveys charge in metals were discovered- the electron. You can just accept this and there is no problem with the fact that these charge carriers happen to have a negative charge. Negative charges flowing one way will correspond to the positive charges flowing the other way. (If you look at solid state Physics, you can have electrons flowing one way and holes flowing the other - that's fine. Also you could imaging positrons flowing in a 'wire' made up of 'Anticopper' and then students would have no problem. (Ignore the practical problem of actually producing a wire of Anticopper!)
Personally, I think it is a very bad idea to try to include what electrons do, in questions of simple circuit behaviour. Electrons in a semiconductor junction or a thermionic diode will behave in a way that you can get your head around. Electrons in a piece of metal are just not amenable to any treatment that relates to your average resistor network. It is not a copout to refuse to use electrons - it's just a pragmatic thing that tells us it is not worth the aggravation and that there are better ways of analysing things. If you don't agree with me then I would ask you whether you would seriously want to consider the way a random gas of electrons flows around a piece of copper when you want to predict its behaviour when you stretch it mechanically. I think you would agree that it is a level too far down for any useful understanding.

@Drakkith - I just got back from a short trip or I would have got stuck in here sooner. You seem to be doing fine, aamof.
 
  • #37
Drakkith already cleared this.I also think that conventional current flow is nothing but a garbage of past . Actually, I was trying to figure out what actually happens about electricity. Surprisingly, I had to receive the info. that electromagnetic field transmits energy instead of electron. It's a crucial truth that average percent of people still believe it . Gradually, my misconceptions are going away . Now ,I have a clear view actually what happens when a battery attached light bulb glow up . But " Electrons those create current flow are supplied by battery?" I think the answer is yes . Because of charge separation the electrons flow from positive terminal to negative terminal of battery through the wire along the electric field direction. These moving electron has magnetic field which is perpendicular to the electric field. Besides the distributed surface charges have electric field parallel to the internal electric field . The combination of both electric and magnetic field results in electromagnetic field. So now we have electromagnetic field that can easily transmit energy from battery to globe with light speed. Therefore the energy used to glow up the bulb. The radiation of the bulbs filament not only produced by that electromagnetic field but also dipole radiation. The radiation of the bulbs filament ( consequence of Bohr's quantum jump) caused by electromagnetic field .We have to remember this electromagnetic field created by current. The conclusion is glowing of bulb depends on current.
Note: Don't forget to confirm me.
 
  • #38
I think you're about as close to the truth of the matter as you're going to get in this thread. :wink:
 
  • #39
I thought I've already known the real fact . But ,are you saying something more I need to explore? What is that?
 
  • #40
Nihad Nazmul said:
Bohr's quantum jump
It is not a 'quantum jump" as in the Bohr atom because it is happening in condensed matter and not just a single atom. I really think you should read (or re-read) a decent textbook, now that you have a number of correct ideas about all this. Your problem is that you are not joining them up in a coherent way. Asking a whole random selection of questions is not the best way to get on top of this. You need a structure for your knowledge and one cannot build one on ones own (unless one is exceptionally gifted - like Max Planck). I have a feeling that, even if you were to get answers to this particular list of questions, you would simply come up with another set. Try to approach this in the conventional way and it will deal with questions, one at a time, and in a formal way. It really does work very well for other people, you know.

PS My view is that there is never any answer to the question "What is 'really happening' here". It's just a set of layers of a model which need to be cleared, one at a time, rather than trying to delve too deeply into a few localise regions of a subject.
 
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  • #41
Nihad Nazmul said:
But what is the role of electromagnetic field?
As Drakkith said, the field transports the energy. Are you familiar with the Poynting vector and Poynting's theorem? I think that would be the next thing for you to explore.

In an AC or DC circuit, such as those you find in residential wiring or household appliances, energy is not transported by the current inside the wires. Instead, energy is transported by the fields outside the wire.
 
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  • #42
DaleSpam said:
In an AC or DC circuit, such as those you find in residential wiring or household appliances, energy is not transported by the current inside the wires. Instead, energy is transported by the fields outside the wire.
In other words, an electrical energy is transported through the insulators, not through the conductors. Quite shocking but true :smile:
 
  • #43
SO steer clear of live spaces! :rolleyes:
 
  • #44
I know Bohr's quantum jump doesn't act main role here . But it happens in a little quantity with other radiations. As electromagnetic field transmits energy I brought that in description . My random question was for messing up current and energy transmission and maybe for the reason questions have stopped peeking. It is true that what really happens can't be watched by shooting camera ? But ,explaing reasons real fact can be depicted and models do that. I was trying to understand by applying models. @sphiecentecur

Yeah,I have idea about poynting vector .Energy transmits by electromagnetic field as electromagnetic wave and the quantity of energy in area per unit is called poynting vector. The direction of energy is perpendicular to that electromagnetic wave . In a battery attached light bulb, from battery converted energy transmits through poynting vector by electromagnetic field of surface vacuum in wire. @DaleSpam

That is why Arnold Sommerfeld (1952) has pointed out, metals are good conductors of current but nonconductors of energy. Metals conduct current but space conducts energy and the best conductor of electromagnetic energy is the vacuum! @zoki85
 
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