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Re: Light bulb ohmicity



But we often do an Ohmic heating lab in which a heating coil of nichrome
(or even a resistor) is immersed in water and the temperature rise is
limited to 5-10K.

5-10 K? Funny unit to use! The temperature rise typically found
in tungsten filament operation is more like 2500 degrees C. If
the glass envelope gets too hot (meaning above 100 degrees C)
the lifetime of the bulb will be significantly shortened by the
water outgassed from the glass.

The ohmicity of tungsten light bulbs near their operating design
centers is about 0.5 according to a table I found at
http://www.picc.com/ under "GENERAL LAMP INFO".

Leigh

A measure of "ohmicity" might well be in order here. I'm at
home today nursing a cold, and I don't have access to the
references (and laboratory) I would like, but a good measure
might be the quantity

V dI
r' = --- ----
I dV