Question

When current flows through a wire how fast is it flowing? When you want to wire an object that needs electricity to flow through it, it would instantly(Less than a blink of an eye) would work! Do you have any ideas?

Answer 1

@waterineyes @ghazi @henpen @Mikael @shivaniits @eyust707 @Jemurray3 @Carl_Pham

Answer 2

That's not a simple question. It depends on the nature of the conductor -- size, shape, any associated circuit elements. People designing microwave circuits have to worry about these things, and here is a body of methods devoted to it. You might start by googling "transmission line analysis."

The bottom line is that the signal itself propagates at some fraction of the speed of light, probably of order 10-50%. Which is, nevertheless, extremely fast, and for many practical purposes can be regarded as nearly instantaneous.

The electrons themselves also move, generally, back and forth if it's an AC signal, and steadily in one direction for DC, but this "drift velocity" is quite slow, a few mm per second is about the right magnitude.

Answer 3

Im kinda confused... How is that the signal moves that fast but the electron itself does not :S Could you define both of them for me.
I might be mixing up my information here @Carl_Pham

Answer 4

Because the signal can move much faster than the electrons. Take a look at a classic example in mechanics:

http://en.wikipedia.org/wiki/Newton%27s_cradle

You can SEE that the "signal" of "get moving!" is passed through the line of balls much faster than the balls themselves move. That's what's going on with an electric signal. The first electron gets a kick in the pants from the electric field, and starts to move. That generates a new elecrtic field, which along with the original one kicks the next electron in the pants, which then moves, generating still more changes to the elecrtic field, and so forth.

Do not confuse an electrical signal with the actual movement of electrons. The two are not at all connected, just as the motion of a wave does not represent the same kind of movement of the water molecules in the water.

Answer 5

I shouldn't say they're not at all connected, because ultimately the electrical signal is caused by the movement of electrons -- what I mean is the two are not one and the same thing. Movement of elecrtons causes an elecrtical signal, but it isn';t the same as an electrical signal.

Answer 6

"How is that the signal moves that fast but the electron itself does not :"
I think the simplest answer is this:
There already electrons present in the conductor of your circut. As soon electrons begin to flow they "push" the closest ones, which then "pushes" the next ones, which then pushes the next... all the way until the point you are measureing. The electrons themselves move a very short distance relative to the conductor. Since the conductor is generally very long we see results far away in a short amount of time. Thus if you measure the speed of the electron it is minimal, however, if you measure the speed that the signal travels through the wire it is almost instantaneous.

Electrons aren't actually pushing each other but you can think of it that way.

Here is a drawing that might help; imagine you have a really long tube filled with balls, if you push just one ball into the end, almost instantly you will see a ball fall out of the other end. The same concept exists with conductors and the flow of electricity.

Answer 7

interesting! Thank you all!

Answer 8

Now I know the idea.
It all about the signal... And its pretty fast :P

Answer 9

@Carl_Pham
@eyust707

Is the electrical signal the cause of the magnetic field?
That signal is the cause of all the effects of current's flow in a conductor right?
Not the actual movement of an electron?
Magnetic field, heat, any other effect. Is all due to that signal right?

Answer 10

That signal is 96% close to the speed of light in all cases.
In all shapes/sizes/lengths of a copper conductor?