"Greg Mayman" bravely wrote to "Mike Ross" (26 Sep 03  08:03:00)
 --- on the heady topic of "VEHICLE LED'S"

 GM> But I was debating whether the lamp filament subjected to a
 GM> changing input voltage approximated more to constant power (as
 GM> you claimed) or constant current.

What I tried to explain was that the power change was less than the
current change. For example in a normal resistor the voltage and current
would normally follow each other. According to P=I^2R & P=V^2/R power
would increase as the square of either one changing. But the lamp
filament tends to depart from this power law in that the square
root of the power change is slightly less than the current change. This
happens because the resistance of the filament increases as its applied
emf is raised. According to the values I had picked around nominal, and
not your extreme selection, this was what it showed.


 GM> Why did you try to introduce this business of the light output of
 GM> the filament?

I guess because the idea was to compare the power input to the visible
light output as a sort of figure of merit or comparative efficiency.
Maybe it didn't really apply.

 Mike
 ****

... Power is obtained by current meeting resistance
--- Blue Wave/DOS v2.30