Re: Bending of Ohm's Law was Re: Gap Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net>
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Saturday, February 28, 2004 9:10 AM
 > Subject: Re: Bending of Ohm's Law was Re: Gap Question
 >
 >  > Original poster: dave pierson <davep-at-quik-dot-com>
 >  >
 >  >
 >  > >Awesome!!
 >  > >Any idea where I could find a V I curve chart for a standard light bulb?
 >  >
 >  >     Its a straight line.  A resistance.
 >  >     (pause...)
 >  >
 >  >     AT ANY ONE TEMPERATURE.
 >  >        (To fully plot it, or any, needs a 3D graph...
 >  >         with temp on the other axis...)
 >
 > Nope.. at a constant temperature of the bulb, a tungsten filament bulb will
 > have a very nonlinear V/I curve (reflecting the temperature of the
 > filament).  To say that it is linear at any specific temperature of the
 > filament is pointless, since there is only one combination of V and I that
 > will achieve that temperature, so there's no relationship to be linear or
 > nonlinear.
 >
 > yes, one could conceive of a scheme where one heats a filament by adding
 > power externally, to hold it at constant temperature, and, in fact, if you
 > can do that, you will have a linear resistor.  Oddly, though, in practice,
 > one measures the temperature by measuring the resistance of the filament,
 > and adjusts the power accordingly.
 > This single value behavior is what folks making precision (<0.01 dB) RF
 > measurements depend on with using thermistor probes by the DC current
 > replacement technique.

	I think constant FILAMENT temperature was what was implied there.

Ed