My question is basically what exactly is electricity? I've simply been told before that it's a flow of electrons, but this seems too basic and doesn't show that electricity is instant. What I mean is turning a switch has no delay between that and a light coming on. Is it really instantaneous? Or is it just so fast that we don't notice it?
Answer
It's just so fast you don't notice it. You won't see the effect of the travel time in something like turning on a light, because your eyes aren't fast enough to register the delay, but if you do even moderately precise experiments involving signal transmission and look at it on an oscilloscope, you will find that the travel time is easily measurable. The speed of signal propagation is close to that of light, or about a foot per nanosecond.
(It's worth noting that this is not the speed of electrons moving through the wires, which is dramatically slower. The signal is a disturbance that propagates more rapidly than the drift velocity of electrons in a conductor.)
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