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Lew Hodgett wrote:
>
> James H. Maynard writes:
>
> <snip>
> >Most loads obey Ohm's law. But not all!
>
> I don't know what you were smoking when you were supposed to be in EE
> class; however, must have found some more of it when you wrote this post.
>
> You need to seriously reread it and try to understand what you wrote.
>
> Lew
>
Lew, I guess it depends on what you mean by "Ohm's Law." Ohm's Law was
originally a scientific discovery. To quothe the Encyclopaedia
Brittanica entry on the subject:
"Ohm's Law: in electricity, experimentally discovered relationship that
the amount of steady current through a large number of materials is
directly proportional to the potential difference, or Voltage, applied
across the materials." Thus Ohm's Law was originally the statement that
the current drawn by a load is proportional to the voltage applied to
that load. The resistance, R, or conductance, S, is just the
proportionality constant for that relationship. Thus E = IR, or I = E/R
= SE, where S = 1/R. If Ohm's Law applies to a load, then that load's
resistance R, or conductance S, is a constant. Loads for which the
current drawn is NOT proportional to the voltage are loads for which
Ohm's Law does not apply.
Nowadays, the term "Ohm's Law" is often applied merely to the formula
E=IR, even when R is NOT a constant. In this latter usage, "Ohm's Law"
is merely a definition of resistance: R = E/I, even when R is not
constant. In the later usage, of course "Ohm's Law" applies to ALL
loads, because for all loads a "resistance" may be computed from the
formula R = E/I. But this latter usage of the term is not really a
physical "law" at all: it is merely a definition of what we mean by
"resistance."
I was using the term "Ohm's Law" in its earlier sense, as a description
of a physical law. It seems that you, Lew, have been using the term in
the latter sense: not as a physical law at all, but merely as the
definition of resistance.
No, I was NOT smoking anything when I studied electrical engineering.
Nor am I smoking anything now. An apology is in order!
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