How fast do electrons travel when moving as an electrical current through copper wire?

Asked by: Leon Taylor

Answer

The actual velocity of electrons through a conductor is measured as an average speed called drift speed. This is because individual electrons do not continue through the conductor in straight line paths, but instead they move in a random zig-zag motion, changing directions as they collide with atoms in the conductor. Thus, the actual drift speed of these electrons through the conductor is very small in the direction of current.

For example, the drift speed through a copper wire of cross-sectional area 3.00 x 10^-6 m², with a current of 10 A will be approximately 2.5 x 10^-4 m/s or about a quarter of a milimeter per second.

So how does an electrical device turn on near instantaneously? If you think of a copper wire as a pipe completely filled with water, then forcing a drop of water in one end will result in a drop at the other end being pushed out very quickly. This is analogous to initiating an electric field in a conductor.
Answered by: Matt G., Engineering Student, University of Texas at Austin and Anton Skorucak, PhysLink.com Editor