Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Do Halogen lamps need ballasts?
Message-ID: <1990Dec6.001951.8252@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <3561@orbit.cts.com>
Date: Thu, 6 Dec 90 00:19:51 GMT

In article <3561@orbit.cts.com> rambler@pnet51.orb.mn.org (Dan Meyer) writes:
>Agreed. isn't quartz a mineral? quite a bit different than glass?

Not all that different.  Quartz is crystals of silica (SiO2).  Most glass
is non-crystalline impure silica.  The impurities are there to change its
properties in various ways, most notably to reduce its softening point.
Pure-silica glass does exist; the only difference between it and quartz
is that the molecular structure of the glass is quasi-random while the
structure of the quartz is a regular array of atoms.  (One of the problems
with working pure-silica glass, in fact, is that it has a tendency to
try to crystallize into quartz.)  I believe the bulbs actually use the
glass, not true crystalline quartz.
-- 
"The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu   utzoo!henry


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