Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!genrad!decvax!yale-com!leichter From: leichter@yale-com.UUCP Newsgroups: net.followup,net.micro,net.physics Subject: Re: speed of electricity Message-ID: <1677@yale-com.UUCP> Date: Mon, 27-Jun-83 15:14:50 EDT Article-I.D.: yale-com.1677 Posted: Mon Jun 27 15:14:50 1983 Date-Received: Mon, 27-Jun-83 23:32:36 EDT Lines: 14 "The speed of electricity" is not a particularly meaningful term. If you ask "how fast do electrons move through a wire", the answer is "very slowly" (a couple of feet per second, at most). However, this is not a figure of much interest. A meaningful question is "How fast can a message be propagated?" (where "message" is very general - it includes the the "message" that the wall switch has been closed "telling" the light bulb to light up), the answer to which is again complicated - because it depends on the exact circuitry - but is something on the order of half the speed of light in a vacuum. A good rule of thumb is that light travels about a foot per nanosecond, so electrical impulses in typical circuitry travel at about 6-8 inches or so per nanosecond. This works out to something like 1/100 of a second to cross the US. -- Jerry decvax!yale-comix!leichter leichter@yale