Re: Light buld in water experement

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: William Beaty <billb@xxxxxxxxxx>

On Thu, 11 Aug 2005, Tesla list wrote:

> Original poster: gary350@xxxxxxxxxxxxx
>  The light bulb will not light up if you take it out of the water.

Try a light bulb standing in an empty cup.

See:
  http://amasci.com/weird/microexp.html#bulb

The gas in modern lightbulbs supposedly is chemically inert argon, but
with a small percentage of nitrogen added to spoil the "long sparks"
effect.

With a 900 watt microwave oven, it pretty reliably pops a bulb every time,
but you have to cook it for up to a minute before the glass melts.  With
my oven, the popped glass is always at the top of the bulb, since the hot
purple plasma will pool a the top and heat the glass in contact with it.

Light bulbs once used vacuum, and they went "bang" when dropped, but
modern bulbs use inert gas.  I think they changed over in the 30s or 40s,
but I'm not sure.   The argon pressure isn't anything like a hard vacuum.
That's why a burned-out bulb usually has a black stain at the top, where
the smoke from the vaporizing filament rose convectively.   If we heat
the light bulb's gas enough, it goes well over one atmosphere, shown by
the outward-going glass bubble on a a microwave-heated light bulb.



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William J. Beaty                            SCIENCE HOBBYIST website
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