On Tue, 02 Jun 2009 20:18:57 -0700, Winston
wrote:

Ned Simmons wrote:

(...)

I understood the article to say not that the filament is thinned, but
that its surface is modified to increase emissivity.

Chunlei Guo:

"We fired the laser beam right through the glass of the bulb and
altered a small area on the filament. When we lit the bulb, we
could actually see this one patch was clearly brighter than the
rest of the filament."

Sounds to me as if the modification was just redistribution of
filament metal. What would happen when you increase the resistance
of a portion of a filament by thinning it? It dissipates more power
because it's resistance is higher (P=I^2R) It glows more brightly
than the rest of the filament but will cause the bulb to fail much
earlier than it would have without the modification, I think.
Would Occam be pleased with this guess?


If the filament has a thin section the power density at that spot will
indeed be higher, but the overall consumption of the lamp will be
lower. (P=V^2/R) The article says, "... we could actually see this one
patch was clearly brighter than the rest of the filament, but there
was no change in the bulb's energy usage."

--
Ned Simmons