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From: rbc@houxu.UUCP (R.CONNAGHAN)
Newsgroups: net.consumers
Subject: Re: Lifetime Lightbulbs
Message-ID: <517@houxu.UUCP>
Date: Sat, 2-Feb-85 13:06:38 EST
Article-I.D.: houxu.517
Posted: Sat Feb  2 13:06:38 1985
Date-Received: Sun, 3-Feb-85 09:09:46 EST
References: <1516@hplabs.UUCP>
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 22

I once had a man who knew light bulbs say that
there was a failure mode called "tungten migration".

The material in the filiment "migrates" in the direction of
the current.  This causes diameter reductions in the light bulb
filiment.  Which causes higher resistance and heat at that spot.
And the bulb burns out.

The effect is worse for DC and less for AC..

Threrefore running a light bulb on half-wave AC (i.e. DC) may
in fact reduce the life of the bulb.



-- 


Robert Connaghan
Microprocessor Group
AT&T Bell Labs - Holmdel, N.J.
houxu!rbc