Difference Of Electron Flow Thru Ac & Dc, and at what speed?

Is it true that electrons flow THRU a DC circuit, but not THRU an AC current?

In ac, electrons just jiggle, and that this jiggling is what is sent along a wire at the speed of light?
How is that so?

In dc, electrons flow thru a wire but at a very slow rate.
How then, can we hear long distance land-line phone conversations, relatively instantaneously ?

Thanks
...Vern

This an analogy only - not perfect...

Imagine a tube filled with balls that just fit in the tube. If you push the first ball, the last ball will move. It is this kind of effect, with the energy being transferred down the wire via lots of 'speed of light' interactions between electrons which are interacting by passing photons between them.

In DC, electron flow always averages to the same direction (not necessarily the intuitive direction - electron flow is from negative terminal to positive terminal, opposite to the direction of current)

In AC, you're right, the electrons are effectively 'pushed' then 'pulled', by repetitively reversing the polarity of the terminals. The average flow turns out to be zero.

Please then, what is current flow.?
What (stuff) is flowing?
Thanks

Current flow was defined as flowing from positive to negative before electron flow was understood. It was defined as a flow of positive charge; it flows from high voltage to low voltage.

However, nothing actually physically moves in the direction of current, since it is negatively charged particles (electrons) which are free to move, and they move from negative to positive.

Ok, so this is true?:
In dc, electrons flow thru a wire but at a very slow rate.

How then, can we hear long distance land-line phone conversations, relatively instantaneously ?

Sorry, I still don't understand what is whizzing down the "dc" line at the speed of light, given that actual "dc electron flow" is so very slow.
Thanks for your help!

It comes down to the 'balls in a tube' analogy again. If the balls begin to flow slowly through the tube, it might take hours before the one you started pushing reacges the other end. However, the one at the far end will react to the push and will fall out of the tube 'almost' instantaneously (if it was right on the edge before the push)

So although the electrons are flowing slowly, they are all interlinked by electromagnetic force and any 'inputs' (talking on the phone being converted to an electric signal, for instance) will be transferred right down the line very quickly, and converted to an output (the speaker on the other phone)

Keep asking questions until you think you have it clear and correct (as I'm sure my answers are nowhere near text book quality! lol)

I would add that it is actually an AC signal that is converted into sound at the receiver, not the DC part. Another popular analogy that also works well to describe this situation is the water pressure analogy.

This sounds similar to something I have been wondering about for a long time. I have one of those glass balls that has a center from which electricity of some sort spurts out and touches the edge of the glass. If I touch it with my hand, the little "lightnings" attract to my hand. I feel a certain charge go through me, but it does not hurt. (I think they are called plazma balls or tesla coils...but I am not sure). Is it ac or dc? What is the little lightnings made of exactly? Why does it go to my hand? (It almost feels alive). When I bought it, the box gave no explanation about it.

Electrons barely move at all in a circuit, but their energy ... ZIP! ... it moves through faster than THE SPEED OF LIGHT. I'm not actually sure about the difference in speed/energy/movement in AC and DC, although AC (alternation current) sends through alternating pulses of electricity, like a wall socket, but DC (direct current) sends a continuous blast of electricity all at the same rate, like a battery.

If the energy moved faster than the speed of light, I very much doubt that propagation delay in asynchronous electronics would be an issue.

Be clear - it is not the energy of the electrons; electrons transfer the energy.

AC is alternating current, not alternation current.

A 'know nothing' cretinoid #1 on steroids.






This post has been edited by fivedoughnut on Jun 28 2007, 08:15 PM

In AC the electrons may be wiggling but the current flow through.
Could one compare it to an energy transfer created by their continuous hitting
like you shoot pool, the only difference being there are two players hitting the balls from opposite sides :)

But then again, what exactly are transmitted, in physical terms?
I know, the current right, but what is it? Please don't say Ampere :)
Also why does it wander one way, why not both ways?
Entropy?

I remember when i learned Electronics, this kind of thing wasn't discussed at all. If that would have been the starting point then i would have become much more interested. They didn't even discuss that the electrons flowed the opposite way as described in the schematics. I think the States have changed its schematics to describe it right but Europe hasn't?

i have goggled on it but seen no physical explanation, only the math describing it?
Could it be? naaee.. Magic? :)

This post has been edited by yor_on on Jul 17 2007, 08:59 AM

Energy is transmitted in the form of electric waves, in ac the energy moves in waves of alternating polarity, while in dc the electric field is constant. In either case the electric field creates a potential across any load in the circuit and energy is transfered via the field from the power source to the load. Energy flows from the source to the sink (load) because of a difference in potential, which is essentially, because of entropy (I think).

Now my friends, after long and diligent searching i've come to the conclusion that current are,, Dare i say it Dare I! Y E S .. are the life giving force of Ra.
Prove me wrong :)

If we don't have a good physic's explanation of current after what? 100 years we should tip toe very quietly around Teslas theories i think :)

This post has been edited by yor_on on Jul 19 2007, 11:00 AM

Simply put, current is the average rate of charge passing through a x-sectional area. It is not a physical entity. Charge is a fundamental physical property - current is the measure of how quickly it is 'moving'.

This post has been edited by bm1957 on Jul 19 2007, 11:37 AM