Re: Optical pyrometers, was R = V/I ?

[Leigh Palmer <palmer@SFU.CA>]

> I've regarded the problem of the filament area as too hard, so we've never
> calculated a value for the S-B constant. Apart from finding the length and
> thickness of the coiled wire, there is the question of how the coiled coil
> behaves: I imagine it is in part like a hot cavity inside, with not all of
> the surface facing outwards.

It is actually an easy problem. Only the gross outside cylinder matters.
The hard part will be measuring it, a problem we solve by using a long
distance microscope which is included in the optical pyrometer.

I see you have taken a hand lens to the filament before. I consider the
coiled coil to be a major technical triumph of the twentieth century.
Tungsten is, after all, a very refractory, brittle metal. So how can
such an exquisite structure be drawn and shaped from such a metal?

While I don't use light bulbs as examples in Ohm's law demonstrations,
I do devote time to them in lectures. They are wonderful mundane
technology, and I could build an excellent inquiry science module for
elementary schools around light bulbs. Of course I would finish with
the microwave demonstration I learned from people in this group. I do
it for my (university) students whenever I have a party at my home. It
is always a big hit.

Leigh