Question

I have a question about the speed of electricity how fast can DC travel through a wire?

Answer 1

well....drift speed of electrons is few mm/sec......but since there r electrons everywhere in wire the electricity reaches other end of wire in no time!

Answer 2

do you want to know how to calculate the drift speed of electrons ?

Answer 3

Electricity is incredibly slow, it's just that electrons are everywhere so they can move just a little bit and their neighbor moves and that causes their neighbor to move, and since they're all crammed together they push each other along.

For example, if you take a bunch of sticks and tape the ends together to make a really long stick. If you poke someone, it's not like the stick in your hand traveled to the end of the stick to touch them and traveled the whole distance, it just sort of had to move a little bit because they were all attached causing them all to move at the same time. So now you see the sticks are little metaphors for electrons where the electric field between them is KIND OF LIKE tape holding them together. (In reality the electrons are really just pushing each other apart and trying to make as much space between them and all other electrons as possible.)

Answer 4

A better idea might be to think of a circuit as you wearing a beaded necklace around your neck. If you start pulling on one side of the necklace all the beads move at the same time.

ALSO:

http://en.wikipedia.org/wiki/Drift_velocity

lol

Answer 5

now i have a question !

for a good conductor like copper, while the drift speed is in order of mm/s, how come the metal discharges so quickly in less than femto second ?

Answer 6

Thank Wikipedia:
"The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave, not the movement of electrons. Electromagnetic wave propagation is fast and depends on the dielectric constant of the material. In a vacuum the wave travels at the speed of light and almost that fast in air. Propagation speed is affected by insulation, so that in an unshielded copper conductor ranges 95 to 97% that of the speed of light, while in a typical coaxial cable it is about 66% of the speed of light.[1]" http://en.wikipedia.org/wiki/Speed_of_electricity

@onaogh That's an awesome question. Does anyone here know?

First, what do you mean by discharging? I think that you might be talking about how the voltage will settle to nothing quickly? Maybe the answer is similar to the main question. The electrons are everywhere. Maybe it takes an incredibly short time interval to spread to a point of what I guess is near equilibrium, where the electrons are staying far away and the electrical potential is the same across the copper.

Answer 7

I'm wondering about that question but in the case of a lone charged capacitor that becomes short circuited. I wonder if it's the intense electrical fields at the capacitor's terminals. Wikipedia uses the formula \(v=\Large\frac{I}{n\ A\ q}\) at http://en.wikipedia.org/wiki/Drift_velocity . Substituting in \(I=\Large\frac{V}{R}\) from Ohm's Law as an approximation, that is \(v=\Large\frac{V}{R\ n\ A\ q}\). Low \(R\) that rises with wire temperature, \(V\) depends on the capacitor and its charge, \(n\) is charge density and would be greater at the terminals, \(A\) is the cross-sectional area, and \(q\) is the charge carrier's charge.