Electron Waves in Copper

Now that the electron is knocked out of orbit and is flowing down a copper wire, is it still a "cloud"? But a "cloud" implies revolving around a nucleus, unless, "flowing" really means hitting every nucleus along the way, forming an instantaneous cloud and then continue flowing.
- James (age 61)
Marietta, GA, USA

Just as the clouds you see in the sky can have all sorts of different shapes, so can the electron clouds. For a first approximation, that moving electron in a copper wire can be pictured as a cloud extending almost uniformly throughout the wire. In practice it is somewhat easier to think of it as being a bit more localized than that. This cloud propagates easily through copper precisely because of its wave properties. The part of the wave that would be scattered from a nucleus overlaps parts that would be scattered from other nuclei. So long as the nuclei are arranged in a perfect crystal, those scattered waves cancel and all that's left is the propagating electron wave.

If some of the copper atoms are stuck out of place or replaced with other atoms the scattered waves don't cancel and there's what's called defect scattering. It varies from one piece of copper to another. Also the copper atoms are wiggling around in the form of little thermal sound waves. That gives what's called phonon scattering, which varies depending on the temperature.

Mike W.

(for background see )

(published on 12/02/2014)