[Phys-L] Re: light bulb transient - amendment

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

At 06:12 PM 11/14/2005, you wrote:
> At 01:36 PM 11/14/2005, Leigh, you wrote:
> > Michael hits the nail on its head, as usual. The filament temperature
> > increases monotonically in time, and so too does the brightness of
> > the filament. However, before Michael pointed out what the actual
> > question was I didn't see it. John Denker's question would be a good
> > one to use on students for teaching purposes, but not on examinations
> > to test their knowledge of physics.
> >
> > Leigh
>
>
> Can anybody see the difference between a filament temperature
>   that increases monotonically, and a filament temperature that
>   increases uniformly?
>
> :-)
>
> Brian Whatcott    Altus OK    Eureka!


Oops! I mispoke.  If we suppose a filament of three separate resistivities
(say low/high/low R) then the high resistance section will heat
non-uniformly as I proposed - but temperature monotonicity fails for the
center section when the lower resistance sections heat. I believe that this
was the thrust of Ken Fox's 3 lamp demo?



Brian Whatcott    Altus OK    Eureka!
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