Re: halogen bulbs

[Leigh Palmer <palmer@sfu.ca>]

David Dockstader exults:

> Boy did you folks do a great job with my halogen question!  I'm glad I asked.
> Rarely have I learned so much with so little effort.

I agree wholeheartedly. It is my belief that a physics teacher
ought to know more about "how things work" than anyone else a
child is likely to meet in her community. In the frame of
reference of the child who is just discovering the world
"mundane" and "interesting" are not antonyms!

But I (an unreconstructed child) want to know a bit more:

My cheap "torchiere" floorlamps have brightness controls on
them. In light of what I've learned here it seems clear to me
that running these lamps for either short times at high
temperatures or long times at lower temperatures is likely to
shorten their bulb life. This is an important discovery, I
think, given that a 300 W bulb costs C$4.00.

The brightness control does provide protection against current
surge because one turns the lamp on slowly. I don't know for
sure, but I suspect the device is some sort of SCR since it
does make radio interference. There is a variety of devices
because one of my lamps has a two-level switch instead of a
continuous control. I have seen the lamps themselves sold for
as little as C$15 (less than US$11), and they include a 300W
bulb. Are these lamps with brightness controls sold as part of
a Chinese plot to sell expensive bulbs? I read Vance Packard's
books; this wouldn't be anything new.

Leigh