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Re: R = V/I ?



I begin (finally) to see where you're coming from. I use the term
"resistance" of a device as I would "pressure" of a gas - a physical
parameter with a clearly defined meaning, whose value depends on contingent
conditions. "Ohm's Law" I teach as the statement that for some materials
(notably metallic conductors) the resistance is constant (wrt applied pd in
particular), at constant temperature.

I think this usage has some justification. After all, in solid state
physics we (attempt to) derive the dependence of conductivity (and hence
resistance) on concentration and mobility of charge carriers, giving the
parameter a more general physical significance.

I have no problem with resistivity as a physical quantity. The
resistivity of tungsten at 2800 K has a meaning which I identify
as a physical quantity. The resistivity of a light bulb, however,
has no evident physical meaning.

Leigh