On Mon, 05 Jan 2015 02:42:16 -0800, mike wrote:

On 1/4/2015 7:37 PM, Jeff Liebermann wrote:

100 watt incandescent bulb on a desk lamp? Doesn't that get rather
warm and possibly hot enough to shorten the life of the bulb?

By how much?
What's the added surface temperature?
Add that to the filament temperature.
What's the percentage increase in filament temperature?

Dunno and I don't have an easy way to measure filament temperature.
What I do know is that if I insert an overpowered incandescent light
bulb in my marginally ventillated Ledu desk lamp, it will burn out
fairly soon. The fixture has a sticker on the lampshade inscribed
with:
Caution: To reduce the risk of fire, use 75 watt
type A lamp or smaller.
There's no indication of exactly what will catch fire.

More likely, it shortens the life of the phenolic socket and switch.

The socket is mostly ceramic, although the insulator might be
phenolic. I can't see the switch. The wiring is covered with heat
protecting sleeving. The insulation might deteriorate from long term
overheating but looks like it will survive nicely with normal use.

My guess(tm) is that the 75 watts is mostly from the UL testing, which
certifies that the appliance will not start a fire or electrocute the
owner. UL testing does not test for appliance lifetime or even
survival. I'm not familiar with how UL tests such things, but I
suspect it's something simple like burying the light in newspaper. I
couldn't find any data on incandescent bulb lifespan versus operating
temperature.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558