Re: Slightly OT. Heat and a Bench Light ...

On Mon, 7 Jul 2008 09:53:39 +0100, "Arfa Daily"
<arfa.daily@[EMAIL PROTECTED]
> 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...




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Jeff Liebermann     jeffl@[EMAIL PROTECTED]
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