[TheForge] We'll leave the light on for ya...was rod ovens

[Charles C. Wales]

Stephen McGehee wrote:
> 
> Some light bulb basics here folks:
> A regular incandescent bulb puts out appx. 97% heat and 3% visible
> light.  If you look at the end of the bulb at the words and numbers, you
<snip>
It doesn't make any difference whether the energy emitted from the bulb
is infrared or visible.  If the energy doesn't excape from the
enclosure, it heats the enclosure.

<snip>

> To extrapolate on the above theory, you can buy 240Volt bulbs with a
> standard base.  A 240 V, 100 Watt bulb consumes 50 Watts at half
> voltage(120) so if you put one of these in the impossible to reach
> fixture above your grandmas attic stairs, it will last 10 years...  

<snip>

Not quite. The wattage as a function of voltage is E squared/R. So if
you run it on half voltage, you get one quarter the wattage.  This is
complicated by the fact that the resistance of the filament varies with
temperature. I wish I could elaborate on that, but . . . . .

Chuck, Bluebird Forge, Stockbridge, MA