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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
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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.