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From: mag@whuxlm.UUCP (Gray Michael A)
Newsgroups: net.consumers
Subject: Re: light bulbs
Message-ID: <669@whuxlm.UUCP>
Date: Tue, 5-Feb-85 08:31:50 EST
Article-I.D.: whuxlm.669
Posted: Tue Feb  5 08:31:50 1985
Date-Received: Wed, 6-Feb-85 04:56:34 EST
References: <3362@alice.UUCP> <681@aluxe.UUCP>
Organization: AT&T Bell Laboratories, Whippany
Lines: 25

> ****                                                                 ****
> From the keys of Steve Henning, AT&T Bell Labs, Reading, PA aluxe!2141smh
> 
> > Light bulbs that last longer do so by running cooler, hence more
> > efficiently.
> 
> This article had a lot of good ideas and good analysis but this flip
> remark flopped.  Tungsten lamps that run cooler give off much less
> light per watt, thus the lumens per watt is very low, thus the
> efficiency is very very low.

There is an inconsistency in the reply above.  "Much less light per watt"
means that there must be, correspondingly, much more heat per watt.  This
would lead to running hotter, not cooler.  Bulbs have only two forms
of power dissipation - heat radiation and light radiation.  The sum of
power in each component must, by conservation of energy, add up to the power
that the bulb uses.  The less power dissipated as heat, the more dissipated
as light; therefore, the light-producing efficiency of the bulb increases
as it runs cooler for any given wattage.  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.

I think this is what Steve Henning meant.

Mike Gray, BTL, WH