Re: How fast does electricity travel through a wire?

The speed of electricity through a wire is a bit of a complex question. It 
depends on whether you are considering the rate at which electrons 
themselves flow along a wire or whether you are considering the rate at 
which an electrical signal passes along a wire. 

In the first case, electrons themselves move quite slowly - about 100 
micrometres per second (or, from another perspective, 1 metre in about 2.8 
hours!) Clearly, this is not what we observe when we turn on a light switch.

Ideally, electricity moves at the speed of light. Imagine a tube full of 
marbles. If you push a marble in at one end of the tube, another marble pops 
out the other end almost instantaneously. Even if the individual marbles are 
moving very slowly, the marble "wavefront" is travelling at a very high 
velocity. 

In the real world, things are not quite so tidy. Electricity flowing through 
a gas, or having to work its way through electronic components such as 
resistors or capacitors, can be slowed to speeds of 60 to 80 percent of 
light speed. However, that's still fast enough that you can safely expect 
the light to come on as soon as you flick the switch.

See this site for more detailed information:
 http://www.itwlinx.com/protection_reference.htm