On Wed, 27 Jun 2007 02:19:52 GMT, the renowned Eeyore
wrote:



Arfa Daily wrote:

"Eeyore" wrote
Arfa Daily wrote:

Why does the heat from the anode of a power tube readily radiate across the
vacuum, but the heat from the filament of a vacuum light bulb seems not
to? d;~}

Both do. It's called infra red radiation.

There's also conduction too.


Agreed that *should* be the case, but the fact is that the envelope of a
vacuum light bulb remains substantially cold in use, whilst a 6L6's envelope
will take the skin off your fingertips after a few minutes use ...

What lighbulbs have *vacuums* in the bulb ? It's normally filled with a
non-reactive gas mixture.

Graham

Many high voltage/low power bulbs are vacuum, IIRC. Don Klipstein says
break-even is 6-10W/cm of filament.

http://members.misty.com/don/bulb1.html


Best regards,
Spehro Pefhany
--
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