# How fast does electricity travel?

Discussion in 'Off Topic' started by Clair de Lune, May 25, 2009.

1. ### Clair de Lune Banned

Joined:
Sep 24, 2008
Messages:
762
1
I don't think it's as fast as light right?

If there is a 100 mile long metal rod and I charge the one end, how long will it take til the party on the opposite end feel it?

How about a glass tube filled with water?

I assume the speed of conductivity depends on the material.

#1

Joined:
Oct 9, 1999
Messages:
11,929
12
#2

Joined:
Oct 8, 2003
Messages:
6,967
0

#3
4. ### spidey07 No Lifer

Joined:
Aug 4, 2000
Messages:
65,481
2
It depends.

Same as the speed of light though fiber optic cabling - it depends.

#4
5. ### Crono Lifer

Joined:
Aug 8, 2001
Messages:
22,995
1,027
"Free electrons in a copper wire move to random directions with the speed of 1.3e6m/s even in the case of no electric current, which means it is not in electric field. This velocity is called "Fermi velocity" and it exists even under 0 absolute temperature. It is not heat energy and originated from indefinite theory of quantum mechanics. Since electric current is average flow of free electrons, in other word "drift velocity", electric current doesn't exist under this circumstance.

When voltage is put on both sides of a conductor, free electrons increase the speed in proportion to the electric field and by lattice oscillation, lattice defect, and collision with impurities, they will be scattered to different directions from the electric field and lose the speed to the direction of the electric field. Therefore it doesn't increase the speed infinitely and it will keep certain average velocity. That means collision functions as a kind of friction.

As for copper, the time interval between collisions is 5.26e-45 seconds and average drift velocity is,

4.62e-3 (m/s) / (v/m).

It means that when 1V voltage is put on both ends of 1m long copper wire, the velocity of free electrons to length direction is 4.62 mm/s. It seems amazingly slow but since electric charge of electrons is -1.6e-19c, 12.6A electric current flows in the 0.5mm copper wire with this speed. You see how large the number of free electrons is."

http://www.cartage.org.lb/en/t.../Mysteryofelectric.htm

#5
6. ### tasmanian Diamond Member

Joined:
Dec 22, 2006
Messages:
3,813
1
Depending on the medium, some percentage of 299,792,458 m/s.

#6
7. ### Crono Lifer

Joined:
Aug 8, 2001
Messages:
22,995
1,027
Depending on my energy, I move at some percentage of 299,792,458 m/s

#7
8. ### heymrdj Diamond Member

Joined:
May 28, 2007
Messages:
3,800
11
Depending on what I had for dinner, I too move at some percentage of 299,792,458 m/s .

#8
9. ### newb111 Diamond Member

Joined:
Oct 8, 2003
Messages:
6,967
0
Depending on what my roommate had for dinner, i too move at some percentage of 299,792,458 m/s

#9
10. ### Jeff7 Lifer

Joined:
Jan 4, 2001
Messages:
41,601
7
Text

(Not mine, like many things, it's just something I found somewhere.)

#10

Joined:
May 19, 2003
Messages:
23,120
64
Fast.

#11
12. ### edro Lifer

Joined:
Apr 5, 2002
Messages:
24,338
66
The speed of light.

#12
13. ### her209 No Lifer

Joined:
Oct 11, 2000
Messages:
56,361
4
Instantaneous. Think of a a cylinder packed with BBs. Now if you shove a BB in at one end, at the other end, a BB pops out at the other end.

#13
14. ### Pheran Diamond Member

Joined:
Apr 26, 2001
Messages:
5,822
30
As some have already pointed out, the answer to your question is however long it takes light (electromagnetic waves) to travel through the medium in question. In unshielded copper, that's .96c, so the voltage will propagate to the other end in about 559 microseconds. Some people have mentioned the speed of electron flow, which is actually quite slow, but what you asked about is voltage (EM field), which does propagate at lightspeed.

#14

Joined:
May 6, 2007
Messages:
4,819
1
No.

#15

Joined:
May 6, 2007
Messages:
4,819
1
No.

#16
17. ### Pheran Diamond Member

Joined:
Apr 26, 2001
Messages:
5,822
30
Congratulations, you have invented time travel.

#17
18. ### RESmonkey Diamond Member

Joined:
May 6, 2007
Messages:
4,819
1
I'm still LOLing at the comment.

#18
19. ### her209 No Lifer

Joined:
Oct 11, 2000
Messages:
56,361
4
speed of electricity != speed of electron

#19
20. ### olds Elite Member

Joined:
Mar 3, 2000
Messages:
48,863
86
Cheaters. Let him do his own homework. :laugh:

#20
21. ### heymrdj Diamond Member

Joined:
May 28, 2007
Messages:
3,800
11
Why, when i thought of his analogy, did i think of an enema .

#21
22. ### RESmonkey Diamond Member

Joined:
May 6, 2007
Messages:
4,819
1
I fail to see the relevance of this post. Are you saying electricity is instantaneous? Because it isn't.

#22
23. ### Fox5 Diamond Member

Joined:
Jan 31, 2005
Messages:
5,958
1
Electricity travels near the speed of light. The electron mobility is much much slower.
Her209's thinking isn't entirely off. It's not instantaneous, but when that first electron goes into the wire, the first electron at the other end pops off at something close to the speed of light, but it will be quite some time before the electron that started it all reaches the other side.

#23
24. ### spidey07 No Lifer

Joined:
Aug 4, 2000
Messages:
65,481
2
It depends on your school of thought. Our measured understanding of this force is just that - measured. Faster then light state changes have been observed. You idea of instantaneous electricity is not that far fetched. But with our current misunderstanding then it isn't.

We can't even understand gravity.

#24

Joined:
Aug 4, 2000
Messages:
65,481