Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site voder.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!sdcrdcf!hplabs!nsc!voder!gino From: gino@voder.UUCP (Gino Bloch) Newsgroups: net.consumers Subject: Re: light bulbs Message-ID: <666@voder.UUCP> Date: Fri, 8-Feb-85 14:04:23 EST Article-I.D.: voder.666 Posted: Fri Feb 8 14:04:23 1985 Date-Received: Mon, 11-Feb-85 04:37:02 EST References: <3362@alice.UUCP> <681@aluxe.UUCP> <669@whuxlm.UUCP> Organization: National Semiconductor, Santa Clara Lines: 21 [sacrifice for bug] > For an extreme example, look > at a pair of 20 watt fluorescent tubes: they give off far more light > than a 40 watt bulb, and they only get faintly warm. You are comparing blackbody radiation (filament bulb) with a mixture of blackbody and line radiation. The reason the fluorescent tubes stay cool is that they DON'T radiate as a black body, so lots of what comes out of them is visible. The reason reduced voltages on filament bulbs makes them LESS efficient is that they run at lower temperatures at the lower voltages, thus more of their (blackbody) radiation is in the infrared, thus less of the applied power results in radiation that stimulates our retinas. Any light bulb can radiate invisible radiation (IR, UV) and can also transfer heat (molecular kinetic energy) to its surroundings by conduction. This, as well as invisible radiation, is a source of inefficiecy (ie, waste). Maybe someone who is taking a lab course in thermo can measure all this stuff and end all this idle speculation ... -- Gene E. Bloch (...!nsc!voder!gino) The opinions expressed above are accidents.