I understand that the electrons themselves in a material travel fairly slow, but I’m talking about actual signal propagation. The speed of an electrical signal traveling through copper can achieve very high fractions of c, but the speed of sound in copper is only around 5010m/s. What causes the disconnect?
In: Physics
**An electrical signal travels at the speed of light**, which in copper is about 200000km/s.
If electrons were only pushing against each other either by bouncing or through their electrostatic charge, then the wave would be traveling at the speed of sound but this is not what happens in reality.
When you connect a voltage source to a cable, the difference in potential between the positive and negative sides produces an electric field. This field travels through the cable at the speed of light and is responsible of the movement of electrons.
To answer your question, the disconnect happens because electrons are not only pushed by other electrons but also by the electric field traveling through the cable, which acts as a waveguide.
For instance, the average speed of electrons is very low and it’s called “drift velocity”.
EDIT: see the answer below, by u/ChaosSlave51 for a more physically accurate explanation.
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