"Watson A.Name - 'Watt Sun'" wrote in message
.. .
In article nHFSa.95145$OZ2.20552@rwcrnsc54,
mentioned...

"Chuck Harris" wrote in message
...
Hi Ratch,

Ratch wrote:

Wait a minute, if L&M say that Ohm's law is V=IR (which it is
not),
and
materials that obey Ohm's law are "ohmic", then by L&M's definition,
all
materials are ohmic because the resistance formula V=IR is always
correct
for all materials. How is a material defined as "nonohmic"? Ratch

No, not quite, ohmic materials by definition have a current density
that
is *proportional* to the electric field. Or in other words have a rho
that is a simple constant.

j = E/rho, or E = j * rho

If you have a material where rho is not a simple constant, but rather
is
a function of current density, you have a non-ohmic material.

I agree with what you said above.


This applies to either way of writing Ohm's law, because rho and R are
proportional to each other.

Yes, rho and R are proportional to each other, but that does not
answer
the question I asked before (see the first paragraph above). How does
L&M
define something as nonohmic when according to what they say, everything
is
ohmic because it follows V=IR (which they say is Ohm's law).


So, as a result, if R is some function of I, the material is non
ohmic.

I agree with that, but according to what you said about what L&M
writes, that never happens because all materials follow V=IR. Does L&M
mention
nonohmic materials? Ohm's law cannot be both V=IR and constant
resistance
as current varies. Which one does L&M say it is? Ratch


There is no inconsistency.

Yes, according to what L&M says there is. Ratch

I think one has to look at the history of this. When Ohm's law was
defined, it's possible that non-ohmic conductors had not been
discovered. Hence everything that conducted obeyed Ohm's Law.

In that context, V=I*R would always apply. Hence at that time, it was
considered a part of Ohm's Law.

But later, things changed...

Maybe.....I don't know. But that was then, this is now. Ratch