Q How fast do electrons flow in copper wire?
A It turns out that the electrons in copper travel quite slowly even though electricity travels at almost the speed of light. That’s because there are so many mobile electrons in copper (and other conductors) that even if those electrons move only an inch per second, they comprise a large electric current.
The fact that electricity itself travels at almost the speed of light just means that when you start the electrons moving at one end of a long wire, the electrons at the other end of the wire also begin moving almost immediately. But that doesn’t mean that an electron from your end of the wire actually reaches the far end any time soon. Instead, the electrons behave like water in a long hose. When you start the water moving at one end, it pushes on water in front of it, which pushes on water in front of it, and so on so that water at the far end begins to leave the hose. In a wire, the motion proceeds forward at the speed of light in the wire (actually the speed at which electromagnetic waves propagate along the wire), which is only slightly less than the speed of light in vacuum.
From QST June 2000
