Posted to sci.electronics.repair
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Slightly OT. Heat and a Bench Light ...
"Jeff Liebermann" wrote in message
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On Mon, 7 Jul 2008 09:53:39 +0100, "Arfa Daily"
wrote:
The things I do for science !!
Cease complaining. It's your question that I'm trying to answer.
Never mind that I don't know anything about light bulbs.
I have
two other types from the same stable, and one of the boxes has an energy
rating on it, and one doesn't, so I'll have to look next time I am in the
store.
Methinks there will be a difference in efficiency rating. If true,
that implies that the newer smaller bulb is really a Halogen filled
bulb, even though it's not marked as such.
OK. On the diameters. Consider them for all practical purposes, to be a
sphere. The old was 60mm almost exactly, and the new, 50mm almost exactly,
measured with an electronic calliper, so reasonably accurate figures.
Surface area of a sphere is 4Pi*r^2
Old = 4 * 3.14 * 3.0^2 = 113.0 sq cm
New = 4 * 3.14 * 2.5^2 = 78.5 sq cm
The new bulb has about 70% of the surface area as the old bulb.
However, I gotta dust off the college thermodyamics texts before I can
figure out the expected temperature rise given identical power
dissipations. I also gotta lookup the IR transmissivity of glass. The
things I do for science...
--
Jeff Liebermann
Quit complainin' !! I'm helping you figure all about light bulbs with my
question .... :-)
Arfa
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