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From: bl@hplabsb.UUCP (Bruce T. Lowerre)
Newsgroups: net.consumers,net.sci
Subject: Re: lightbulbs
Message-ID: <3478@hplabsb.UUCP>
Date: Wed, 14-May-86 12:56:55 EDT
Article-I.D.: hplabsb.3478
Posted: Wed May 14 12:56:55 1986
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Organization: Hewlett Packard Labs, Palo Alto CA
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> 2) I use Bulbsavers on some of my light bulbs.  Bulbsavers are stick-on
> thermisters, a device that changes from a high electrical resistance
> to a very low resistance when they heat up.
> The theory (well proven by my experience) is that the bulbs last longer
> because the thermister reduces thermal shock to the filament caused by
> the rush of current that normally occurs when turning on a light.
> I have read that the light output of "thermistered" bulbs is decreased
> even at normal operating temperature and have noticed a "yellow shift"
> in the spectrum.
> 
> My question is: how much of a decrease in light output do these things
> cause and what change in the light spectrum does occur?
> 
> BTW, it takes a few seconds for a thermistered bulb to light up.  It's
> quite funny to see the puzzled reaction of people used to instant light
> when they turn one of these suckers on.

It's not the sudden rush of current that is hard on the filament but the
AC current.  I've seen slow motion movies of filaments warming up when
being lit.  The alternating magnetic field plus the softening of the
filament as it warms up causes it to do a lot of "break dancing" (excuse
the pun).