Ratch,

It comes down to a basic ability to read and understand
algebra!

If I tell you that y = m*x + b, and I tell you the variables
are x and y, do I really have to tell you that m and b are
constants?

If they are not constants, then I have to show that they are
dependent on x (or y). To do that I would write them as:

y = m(x) * x + b(x) Which changes the character of the

equation tremendously.

L&M told you that most, but not all materials have a current
density that is proportional to the electric field. Then,
they gave you the equation:

j = (1/rho) * E (9-16)

[not:

j = (1/rho(E)) * E or j = (1/rho(j)) * E ]

and told you it (9-16) was Ohm's Law.

Really, though, whether or not R is ohmic, is immaterial,
as long as you can describe R, the relationship we all
call Ohm's law works... it has to, because R is defined
to make it work.

If you want to argue this further, you really must cite
Georg S. Ohm's research work that shows he was only
interested in being deified over materials that are
purely ohmic, and you really must cite the individual, or
group that first coined the phrase "Ohm's Law" to see what
they meant by it. Citing Resnick, or L&M, or the tooth fairy
doesn't do it. None of them were involved in the deification
process, and as a result their arguments are pure speculation,
or conjecture.

The overwhelming body of evidence in the engineering literature
of the last 100+ years suggests that E = iR is properly named
as Ohm's law, just as most of us think it is.

-Chuck


Ratch wrote:
"Chuck Harris" wrote in message

Eq. (9-16) describes the current density in terms of the electric
field at a point in a conductor (Fig. 9-11). It is called Ohm's law.
materials that obey Ohm's law are usually called ohmic conductors. This
relation enables us to calculate the current flowing through a wire of
length L which is connected to two terminals - points between which
there is a potential difference V....]


Now here is where they crash. They first give equation (9-16) and call
it Ohm's law. Then they say that all materials that obey equation (9-16)
are ohmic. Well, all materials obey the resistivity equation (9-16).
Therefore by their reasoning, all materials are ohmic. They go on to say
that Ohm's law can be used to show the relationship between resisitivity,
current density, and electric field. That is certainly true for Equation
(9-16), but that is the resistivity equation and it stands on it own
independent of Ohm's law. The resistivity (9-16) is used to determine
whether a material has the Ohm's law property, but it is not Ohm's law per
se.




L&M could have said a bit more about what they meant about a material
not following Ohm's law; how they meant that a material that has a non
constant rho is non ohmic. However, I caught the meaning the first time
I read it, so it cannot have been too badly worded.


You were primed to understand it because of your exposure to this
discussion.


The trip from (9-16) to: V = RI is just a straight forward
rearrangement, and substitution. It still states the same thing as
(9-16). A material is non ohmic if R is not a constant.


I don't see L&M saying anything that corresponds to the last sentence
above. Again, the resistance equation V=IR can be used to determine if a
material has the Ohm's law property, but V=IR stands on its own and is not
Ohm's law per se. Look at
http://maxwell.byu.edu/~spencerr/websumm122/node50.html again. Ratch