Last week Marilyn Von Savant answered the question how long does it take for electricity to travel from NY to LA? She said that since it travels at the speed of light, or approx. 186,300 miles per second, it would take about 0.01 seconds.
I think that that answer is wrong for several reasons, and I would appreciate it if the teeming millions can set me straight.
(1) Electromagnetic waves travel 186,300 miles per second in a vacuum, but travel more slowly through a wire. As an adjunct:
(2) Wires provide friction (resistance, impedance) further slowing down the speed.
(3) My understanding is that the electrons that are energized in NY do not travel to LA, but by a series of chain reactions energize existing electrons in LA. I don’t know if this has any relationship to the speed.
(4) In order to get a current, the circuit must be completed. I realize that the electrical stream does not have to return to NY, but can merely be gounded. That won’t appreciably increase the time, but can some one tell me how that completes the circuit?
In a class on Data Communications, the number we used for signal propagation down a wire was 2X10[sup]8[/sup] [sup]m[/sup]/[sub]s[/sub]. This is [sup]2[/sup]/[sub]3[/sub] the speed of light.
Naturally, this should be considered an average value for an average set of conditions. YMMV.
There are two speeds, I think, the first being that 2/3rds bit, the second being the actual speed of electrons down the wire, which I think is about 1 m/s.
Yet another proof that MvS really ought to read up on her competition: Cecil covered this briefly (but accurately) a few years ago.
As for the speed of the electrons themselves, a very thin wire carrying a very high current might be able to reach a meter per second, but it’s usually more like millimeters. The speed of the signal and of the energy is constant for any given material, and is exactly equal to the speed of light in that material, which is always slower than the speed of light in vacuum.
The speed of electricity is a vague term. The electrons travel slower than the signal or power. In any case even the signal travels much slower than the speed of light in a vacuum. Wires have resistance, capacity and inductance which retard the signal.