Speed of Electricity in Wiring - Why near light speed?

[rcgldr]

I don't understand the meaning of the dielectric constant.

Briefly covered in the link I posted:

http://hyperphysics.phy-astr.gsu.edu/Hbase/tables/diel.html

The actual wiki link:

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

 

[foxfyr]

Regarding the travel of an electron in a conductor, I might suggest one examine the relationship of drift velocity to Fermi speed (velocity) and its relationship to conductance.

But still there is the category mistake of equating Fermi velocity and actual electron velocity with the propagation velocity of an electromagnetic field. And if you choose to view this from the perspective of a particle (as distinct from a wave model), then you might want to further consider the refractive index modifying the velocity of particles in a medium for an EM field..

 

[antd]

I've read the thread but I still do not understand.

Can someone help explain how the propagation of an electromagnetic wave is near the speed of light, but the speed of electricity is slow? (the water/traffic light analogies don't make sense to me)

Does 'speed of electricity' mean the speed the electrons are traveling?

http://img59.imageshack.us/img59/9545/switchbulb.png
Could someone explain it using this picture of a bulb receiving electricity from a switch

Let's say the distance from the switch to the bulb is 100 meters. Somehow the bulb will receive electricity almost instantly. Maybe someone could show where the propagation of an electromagnetic wave comes into play?

I thought electromagnetic wave was something to do with virtual photon pairs (not sure how classical explains electromagnetic waves). Maybe this is why it can be fast. Hope someone can explain! :)

edit: I think I'm asking what is the relationship between electromagnetic waves and electrons, and how that relationship results in the bulb being quickly lit up.

 

[NruJaC]

It's much simpler than that. As soon as that switch is closed, a driving force (a voltage), is applied to the electrons in the wire. The bulb receives power as soon as the electrons RIGHT next to the bulb receive the signal (voltage change) to move forward; why does the bulb care if it gets the electrons coming out of the switch or not?

Also, electromagnetic waves ARE a classical concept. They follow directly from Maxwell's Laws (a collection of 4 laws that explain electromagnetic phenomena).

 

[antd]

It's much simpler than that. As soon as that switch is closed, a driving force (a voltage), is applied to the electrons in the wire. The bulb receives power as soon as the electrons RIGHT next to the bulb receive the signal (voltage change) to move forward; why does the bulb care if it gets the electrons coming out of the switch or not?

Also, electromagnetic waves ARE a classical concept. They follow directly from Maxwell's Laws (a collection of 4 laws that explain electromagnetic phenomena).

But how can it be explained in terms of speed?
If the speed of electricity is slow (millimeters per second) how can the bulb light up instantly?

Doesn't the 'electricity' have to travel the whole length of the wire? Or is it something like the single electrons pass it on to a neighboring electron?

 

[f95toli]

The "speed of electricity" IS the speed of the electromagnetic waves; in a way you can think of electrons as the "medium" that the wave travels in (this is not quite correct, but close).
The fact that electrons happen to move around in the medium is more or less irrelevant; there is certainly no direct relation between their speed and the speed of the wave (or equivalenty the speed at which energy can be transfered).

The bulb lights up instantly because the necessary energy is carried by the wave; not the electrons (although in order for the bulb to light up that energy has to be converted from electromagnetic energy to heat via various scattering processes).

 

[antd]

I'm beginning to have a better understanding now!

Although, Wikipedia says 'the speed of electricity' is often confused with 'the propagation speed of an electromagnetic wave'. So in that sense 'the speed of electricity' is the speed of the electrons, and not of the EM wave.
http://en.wikipedia.org/wiki/Speed_of_electricity

The bulb lights up instantly because the necessary energy is carried by the wave; not the electrons

What is the wave made of? Photons?

 

[Dale]

Although, Wikipedia says 'the speed of electricity' is often confused with 'the propagation speed of an electromagnetic wave'. So in that sense 'the speed of electricity' is the speed of the electrons, and not of the EM wave.
http://en.wikipedia.org/wiki/Speed_of_electricity

The usual terminology for the average net velocity of the electrons is "drift velocity". In all of my years of experience I have never heard the drift velocity called "the speed of electricity". Wikipedia is notoriously unreliable.

Maybe the hyperphysics page will help:
http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/ohmmic.html

 

[antd]

Thanks.

Slowly learning not to trust wikipedia ;-)