What speed does electricity travel along a wire?
(Larry, London, England) A: This question is slightly perplexing because we mean many things by “electricity.” When we apply voltage across a wire, this creates an electromagnetic wave that zooms down the wire at the speed of light in the medium. An individual electron travels almost as fast as the signal — about a million meters per second (m/s), but this motion is almost entirely a random, bouncing-around motion. The electron travels this fast without contributing to charge flow. It undergoes many collisions, and doesn’t get far from one collision to the next. Free electrons in the metal act almost like a gas, having billions of collisions per second, says Rod Nave, physics professor at Georgia State University. The electric force gives them a net tendency to drift down the wire, but the collisions “thoroughly scramble” their progress. See figure. The drift velocity is a slow limp on the order of a millimeter per second (about ten times slower than a garden snail). Bonus Question Q:
