Electricity And How Fast Does It Travel?

Question

This may sound like a bit of a silly question. But I am no electrician so do not know the answer!

I was cutting the lawn yesterday and whilst pulling the plug from the extension my fingers were close to the contact pins going to the main source.
And I thought gawd that was close. And started wondering how fast does electricity travel?

For instance: You plug your hair dryer or whatever into the wall socket you switch it on and hey presto hot air comes through it.
Does it travel to the hair dryer at a certain speed or what? Or is it instant? I don’t know!

I am not very good at explaining myself on this question. But am hoping some person will be able to suss out what I am asking

Answer 1

Imagine a hollow cylindrical tube, several yards in length, and filled with spheres lined in its inside. (A diagram would help here, but the idea is that the spheres completely fill the tube, and can move to either side).



Now, picture this 1) If you insert an additional ball in one of the sides of the tube, almost instantaneously, another will drop at the other end of the tube; 2) If you continue to insert additional balls on your side, a stream of balls will be dropping out of the other side, but the actual speed of the individual balls is small. Actually you will recognize that the first ball you inserted will only come out on the other side after all the original balls in the tube were replaced.



This is what happens with electricity. When you drive electrons into a wire, they push the electrons already there in the metal, which push further into it, and further into it, and further into it. The result is that the electrons entering the conductor create a signal that propagates very fast to the electrons on the other side, but the electrons themselves are not making the trip immediately. Physically, they have two speeds: random thermal motion which is fast but in position averages out to zero, and the drft velocity (about 1 millimeter / second) that carries them along the conductor.



Notice that, for an electron that has entered, to exit on the other side, you'd need to replenish all electrons initially in it, so to speak, and that number is trully very high.

Answer 2

Your question is unclear: if you mean by electricity the electric field or potential in a conductor: this travels at the speed of light (in that material) so a little slower than the speed in vacuum c= 2.99E8 m/s. The exact answer is that the speed c' depends on the relative electrical permittivity (eps_r) and the relative magnetic permeability (mu_r) of the material: c ' = c/sqrt(eps_r mu_r).. If you mean the average velocity of the electrons along the conductor: this is called the drift velocity of the electrons. The relation between current and drift velocity is I = A * n * e * v. Here I is the current (Ampere) , n the density of the conduction electrons (1/m^3) , A the cross-sectional area of the wire (m^2) , e the charge of an electron (Q) and v the drift velocity (m/s). Plugging in the numbers for a typical copper wire of cross section .5 mm^2 and a current of 1 Ampere, you find a drift velocity v that's approximately only 35 cm/hour... !! The difference between electron drift velocity and signal velocity can be made clear through an analogy: In pushing a stick across the floor, you might start pushing the entire stick at a speed of 1cm/s, but the moment you start pushing, the other end (almost) instantaneously moves, so the signal "start moving" travels at a much higher speed (in this example the speed of sound in the stick actually) than the stick itself moves...

Answer 3

the direct electric current density j through a conductor is proportional with the number of electrons in the unit volume (n) the charge of an electron (e) and its (drift) velocity v, the velocity at which the electrons move i.e.

j=nev

if you have in mind that velocity it is surprisingly small

When electric current in a material is proportional to the voltage across it, the material is said to be "ohmic", or to obey Ohm's law. A microscopic view suggests that this proportionality comes from the fact that an applied electric field superimposes a small drift velocity on the free electrons in a metal. For ordinary currents, this drift velocity is on the order of millimeters per second in contrast to the speeds of the electrons themselves which are on the order of a million meters per second. Even the electron speeds are themselves small compared to the speed of transmission of an electrical signal down a wire, which is on the order of the speed of light, 300 million meters per second.

Answer 4

well electrons on the conductors travels 0.15mm/s

or to travel 1 meter the electrons requires almost 2 hrs.

really really slow

negligible compare to the speed of light which is 300,000,000 m/s.

electrons can be compared to a train when you push at the end automatically the front of the train will move with the same speed.

the end of the train does not have to go suddenly in front to

say that the train is moving

Answer 5

Depends on the medium, i.e. is there alot of resistance and what is the potential difference applied.



Electron carrying materials are things which have ions floating around (free moving electrons), some conductors may not have as many or may not be made out of 100% ionised material.

Answer 6

Through a good conductor, its close to the speed of light. But through a bad conductor, its considerably less. When I was a kid, I'd put a wooden stick on an electric fence and I'd feel the electricity build up slowly till I had to move it -- it wasn't instantaneous.

Answer 7

it's a lil less then half the speed of light i think. probably depends on the medium

Answer 8

Wow,even the big boys don't know.....exactly.



http://newton.dep.anl.gov/newton/askasci/1995/eng/ENG51.HTM

Answer 9

186,000 miles per second