Turn Your Power Supply into an Ohmmeter - It's Free!

[buck rojerz]

"Sofie" <sofie@olypen.com> wrote in
news:vheca77sefdtd5@corp.supernews.com:

Sir Charles W. Shults III:
That is a good in depth, overly complicated, answer but not the one I
was looking for..... obviously since the Tim Williams posting said
".And besides that, it measures actual in-circuit conditions,
because a resistor is *supposed* to get hot, at least if it's doing
its job..." ..... and since the overly discussed "2 meters and power
supply" ohm meter method can overheat low-ohm resistors..... and the
resistance of any resistor will vary with temperature..... I was
wondering at what exact "hot" temperature the resistor should be at to
make an accurate measurement..... LOL Obviously I am not looking for
any kind of answer here....... I just think that this thread went
bonkers when all the original poster wanted to do is, as Chuck Harris
indicated in his reply post, show off his new found factoid....
however it seems clear that it may not be a very practical and
convenient method as evidenced by the length and tone of the majority
of the reply posts.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

My goodness! FINALLY! An intelligent reply! At least somebody is using
their head, instead of the other end.

 

[William Hayes]

"Watson A.Name - 'Watt Sun'" <alondra101@hotmail.com> wrote in message

So, now that we've had a nice discussion about ohm's law, explain that
fangled volt/amps rating on stuff.
I'm sure someone will note it is "nonohmic" somewhere...

So if a regular diode is nonohmic, what's a schottky diode? Half a
nonohmic? Sort of like the sound of one hand clapping... ;-)

Hey, with this new fangled Newer Math, It wouldn't surprise me.
I'm still getting used to the idea of three Ohm's Laws....

 

[Chuck Harris]

Hi Ratch,

I pulled out my old college physics text just to see what they had
to say, and Lobkowicz and Melissinos, "Physics for Scientists and
Engineers", Vol 2. starts out stating that Ohm's Law is:

j = E/rho, and therefore, E = j * rho

Where j is the current density, E is the electric field, and rho is
the resisitivity.

Then they set a few conditions to make the math easier: a homogeneous
material of constant crossection, and some unspecified length,
and derive the more familiar form:

V = [rho L I]/A = RI, where L is length, I is current, A is
cross sectional area, and R is resistance.

V = RI

From that point on, L&M use the two forms of the equation
interchangably... picking which ever one makes the solution
easier.

So, it would appear that both forms are actually equivalent,
one is more favorable for use in studing materials, and the
other is better for studying circuitry.


-Chuck



Ratch wrote:

It is certainly true that what a professor writes is going to be what
he believes to be factual. And impossible to discern how he came upon his
knowledge. But you have to ask yourself, why did Professors Resnick and
Serway go out of their way to make a point that Ohm's law is a property of a
material and not V=IR? Does that not indicate that they looked into the
matter more closely that their contemporaries? The next time I get to a
good college library, I will look at other college physics textbooks. Ratch

 

[William Hayes]

"Mark Jones" <127.0.0.1> wrote in message
news:Kwmdne6m3vxYSIWiXTWJkw@buckeye-express.com...

William Hayes wrote:
"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in
message news:3f18549d$0$28888$1b62eedf@news.euronet.nl...
Let's go all nuts and talk about ohmistance & ohmistors from
now on
Cripes, You want these guys/gals to actually learn something
??
Did I hear someone say "MHO's?" : )

Hey, next you'll be getting into why Holes Flow.... STOP STOP... I didn't
pun that.. did I ??

 

[William Hayes]

"Ratch" <Watchit@Comcast.net> wrote in message
news:F84Sa.82765$sY2.37667@rwcrnsc51.ops.asp.att.net...

Your link gives two definitions of Ohm's law. The first is the one you
refer to above, in that R=resistivity*length/area. It is a resistance
formula for a conductor with known physical dimensions and resistivity,
but
it is not Ohm's law. .

Dead Banana. ( beating a dead horse dry )

After all, you are calling "the" English [ liars. ]

They coined Potential of Current to Flow = current * resistively of
length/area while Temperature is constant as Ohm's Law.
E = I * R
Voltage = Current * Resistance

"The" English named it after George Ohm.

What part did you fail to grasp ?

The cross section of the conductor has no bearing whatsoever on whether a
material is ohmic or not.

So a Cross Sectional Area of a 00awg Cable has the same ohmic value at
20,000 feet as a 24awg cable at 20,000 feet ?
Surely I'm missing your point.

If you have a conductor made out of a certain material, you can plot the V
vs I curve.

Using what gauge of certain material ?
Using what Temperature Conditions ??
Ever seen a P4 Processor smoke when a fan is not applied to it after a few
minutes of run time ??

If the curve is straight, it is ohmic regardless what the physical
dimensions are--even if the cross section varies from point to point.

If the curve is straight, even if the curve is straight.
This means your processor can not function. It is breaking your Ohm's Law.

If you understand that resistive linearity property of the material, then
you know Ohm's law

I understand the resistive linearity of certain materials that conduct
electrons verses certain materials that do not conduct electronics and each
has a chart that relies heavily on the Gauge of the material and
Temperature.

If you have a conductor made out of a certain material, you can plot the V
vs I curve.

I have a conductor made of air, using 240,012 volts of potential energy
flow, you claim I can determine the plot of Voltage verses Current. Without
having to know the gauge of the air or temperature and why either has an
effect on the current flowing between the potential energy flows. Benjamin
Franklin wrote several papers regarding such flows. You'll find them
interesting.

 

[Ratch]

"Chuck Harris" <cfharris@erols.com> wrote in message
news:bfd1hf$2ai$1@bob.news.rcn.net...

Hi Ratch,

I pulled out my old college physics text just to see what they had
to say, and Lobkowicz and Melissinos, "Physics for Scientists and
Engineers", Vol 2. starts out stating that Ohm's Law is:

j = E/rho, and therefore, E = j * rho

Where j is the current density, E is the electric field, and rho is
the resisitivity.

Then they set a few conditions to make the math easier: a homogeneous
material of constant crossection, and some unspecified length,
and derive the more familiar form:

V = [rho L I]/A = RI, where L is length, I is current, A is
cross sectional area, and R is resistance.

V = RI

From that point on, L&M use the two forms of the equation
interchangably... picking which ever one makes the solution
easier.

So, it would appear that both forms are actually equivalent,
one is more favorable for use in studing materials, and the
other is better for studying circuitry.

Every solid had a property called resistivity. Resistance is determined by
the resistivity, the shape of the solid, and the
placement of the two measurement leads into the solid.

Prof Serway says the same thing about resistance/resistivity as L&M, except
Serway does not call the formula E=rho*J Ohm's law. Instead Serway says
that if the resistivity (rho) is constant at any electric field (E), then
the material is ohmic. That means that E and J are linearly proportionate to
each other. How does L&M define an ohmic material? Ratch

 

[Ratch]

"William Hayes" <wlh56@comcast.net> wrote in message
news:seoSa.89583$OZ2.18630@rwcrnsc54...

"Ratch" <Watchit@Comcast.net> wrote in message
news:F84Sa.82765$sY2.37667@rwcrnsc51.ops.asp.att.net...

Your link gives two definitions of Ohm's law. The first is the one you
refer to above, in that R=resistivity*length/area. It is a resistance
formula for a conductor with known physical dimensions and resistivity,
but
it is not Ohm's law. .

Dead Banana. ( beating a dead horse dry )

??? I have not idea what you mean by the above.

After all, you are calling "the" English [ liars. ]

Who are these "English" people you refer to? A lie is a willful statement
contrary to what one knows to be true. I never called anyone a liar here.
Mistaken perhaps, but not a liar.

They coined Potential of Current to Flow = current * resistively of
length/area while Temperature is constant as Ohm's Law.
E = I * R
Voltage = Current * Resistance

What is "Potential of Current to Flow"? Current exists, it does not
flow. Charge flows.

"The" English named it after George Ohm.

I know that the MKS unit of resistance was name after George. And George
stated that for some materials, the current is
proportionate to the voltage. I don't know who named that material property
after him, do you?

What part did you fail to grasp ?

Whatever you are talking about above.

The cross section of the conductor has no bearing whatsoever on whether a
material is ohmic or not.

So a Cross Sectional Area of a 00awg Cable has the same ohmic value at
20,000 feet as a 24awg cable at 20,000 feet ?
Surely I'm missing your point.

Yes, you certainly are. I am saying that whatever shape the material is
does not affect whether it is ohmic or not. I never said that same length
cables with different diameters made out of the same material will not have
different resistance values.

If you have a conductor made out of a certain material, you can plot the
V
vs I curve.

Using what gauge of certain material ?
Using what Temperature Conditions ??

Doesn't matter. No matter what the shape of the conductor, a V vs I
curve can be plotted.

Ever seen a P4 Processor smoke when a fan is not applied to it after a few
minutes of run time ??

Nope, why should that matter?

If the curve is straight, it is ohmic regardless what the physical
dimensions are--even if the cross section varies from point to point.

If the curve is straight, even if the curve is straight.
This means your processor can not function. It is breaking your Ohm's
Law.

Don't let your mind wander. We are talking about Ohm's law applied to
solids, not to computers.

If you understand that resistive linearity property of the material,
then
you know Ohm's law

I understand the resistive linearity of certain materials that conduct
electrons verses certain materials that do not conduct electronics and
each
has a chart that relies heavily on the Gauge of the material and
Temperature.

The resistive linearity is a property of the material that relies on no
chart whatsoever.

If you have a conductor made out of a certain material, you can plot the
V
vs I curve.

I have a conductor made of air, using 240,012 volts of potential energy
flow, you claim I can determine the plot of Voltage verses Current.
Without
having to know the gauge of the air or temperature and why either has an
effect on the current flowing between the potential energy flows.
Benjamin
Franklin wrote several papers regarding such flows. You'll find them
interesting.

A volt is not a unit of potential energy per se. Remember charge flows,
current doesn't, current just exists. Anyway,
sure you can measure the voltage and current of an arc with the right
equipment and safety precautions. What does does
gauge and air temperature have to do with that? Ratch

 

"Watson A.Name - 'Watt Sun'" wrote:

Hey, I like that.. It has a nice ring to it: "Watson Ohmmeter".

One of the maintenance guys at work gave me a Fluke 23 meter which is
just a yellow cased version of the 73, I believe. Said he sent it to
Fluke but they sent it back because it it was beyond repair or it
would cost more than a new meter. He might have done something really
stoopid like set it to the ohms range and put it on the 480VAC. In
any case, the display comes on, but nothing happens when the test
leads are connected to a V source. Apparently something major has
been zapped. It's been laying around at work for a couple years, it
probably oughtta be tossed in the trash can.

NO NO NO NO NO!!!!
You could put some of your LEDs in the holes where the
meter leads go, make them blink or change colors or something,
and pass the thing off as an experimental DMM that uses
leds instead of leads - it reads the circuit by reflected
light! And the only difference is the letter a

Seriously - it might be a simple repair. As far as the
grungy case - I have on old Fluke 8022 B whose case was
filthy. I took the guts out and washed the thing in a
bucket of hot water with dishwashing soap. I let it soak
for a couple of hours, then scrubbed it with a scrub
brush. Came out clean as a whistle.

The case is kind of
grubby so it's not worth saving for the case. Maybe I should give it
to the theater dept to use as a prop.

Recently the theater guy came over and asked our help desk lady for a
dozen telephone handsets and curly cords. She asked him what they
were going to do with them. He said they were going to use them as
props in a play, the actors would be dancing around with the handset
and the curly cord on stage. He said they would give them back after
the play was over.

Maybe they were going to imitate that Sprint guy: "Can you hear me
now?"...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - 'Watt Sun]

In article <3f1963bf$0$28893$1b62eedf@news.euronet.nl>,
bemelmanx@euronet.nl.invalid mentioned...

"Ratch" <Watchit@Comcast.net> schreef in bericht
news:xscSa.97708$Ph3.10866@sccrnsc04...

"Chuck Harris" <cfharris@erols.com> wrote in message
news:bfbfqe$1jt$1@bob.news.rcn.net...

If you ask engineers what is Ohm's law, they will say E = iR,

Only because they learned it that way. If you explained the
misnomer,
then what would they say?

...they'd say you're a pain in the butt. You belong to the same category
as the ones that always have to say that RS232 is about voltage levels
and has nothing to do with serial ports. Strictly that is correct, but
at the the same time the *entire* world uses the term when referring
to typical serial ports such as COM1 and COM2 on your PC.

E = I * R. Ohm's Law. Always has been, and always will be.

And to think that I started this whole 'discussion' with just a..
oh well, forget it.

Same thing happened with the RJ-45 plugs for Cat5 cables.

--
Thanks,
Frank Bemelman
(remove 'x' & .invalid when sending email)

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Watson A.Name - 'Watt Sun]

In article <pRdSa.85516$sY2.38332@rwcrnsc51.ops.asp.att.net>,
Watchit@Comcast.net mentioned...

"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in message
news:3f1963bf$0$28893$1b62eedf@news.euronet.nl...
"Ratch" <Watchit@Comcast.net> schreef in bericht
news:xscSa.97708$Ph3.10866@sccrnsc04...

"Chuck Harris" <cfharris@erols.com> wrote in message
news:bfbfqe$1jt$1@bob.news.rcn.net...

If you ask engineers what is Ohm's law, they will say E = iR,

Only because they learned it that way. If you explained the
misnomer,
then what would they say?

...they'd say you're a pain in the butt. You belong to the same category
as the ones that always have to say that RS232 is about voltage levels
and has nothing to do with serial ports. Strictly that is correct, but
at the the same time the *entire* world uses the term when referring
to typical serial ports such as COM1 and COM2 on your PC.

And you would rather blame the messenger than appreciate the message.

E = I * R. Ohm's Law. Always has been, and always will be.

You are in denial. Ratch

And you really are turning into a pain in the butt. At least you're
on topic.

It kind of reminds me of all the spam artlcies in the newsmedia.
They're arguing about the definition of spam, as the whole world is
drowning in it!

There's so much bickering going on, that one would think that no one
understands the problem. I wouldn't be surprised if the lawmakers did
the same thing they've done the last few years: skip it for now and
worry about it later.

--
Thanks,
Frank Bemelman
(remove 'x' & .invalid when sending email)

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Fred Abse]

On Sat, 19 Jul 2003 03:23:48 +0100, William Hayes wrote:

I'm piqued. I'd like to know why you think E=I*R is not "Ohm's Law".

Ohm's Law states that the current in a conductor is proportional to the
potential difference across its ends.

I=V/R is an equation *deriving* from Ohm's Law, having decided upon an
arbitrary constant of proportionality called resistance.

The concept of resistance *arises out of* Ohm's Law.

IME, it's a lot easier to teach that way, too.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Fred Abse]

On Sat, 19 Jul 2003 02:40:09 +0100, William Hayes wrote:

So, now that we've had a nice discussion about ohm's law, explain that
fangled volt/amps rating on stuff.

Volt-amps refers to AC. It's just the product of voltage and current
without paying any attention to phase. True power (watts) may or may not
be the same depending on the nature of the load, if it's resistive, watts
= VA, if it has a power factor not equal to unity, true power is less
than VA. VA only equals true power where voltage and current are in
phase, ie PF=1.

This brings up the conept of reactive volt-amperes, aka (wrongly)
"wattless power"

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Fred Abse]

On Sat, 19 Jul 2003 06:23:16 +0100, Mark Jones wrote:

Did I hear someone say "MHO's?" : )

They were nice! Shame we have to call 'em Siemens these days

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Tim Williams]

"Fred Abse" <excretatauris@cerebrumconfus.it> wrote in message
newsan.2003.07.19.11.29.21.68081.645@cerebrumconfus.it...

Did I hear someone say "MHO's?" : )

They were nice! Shame we have to call 'em Siemens these days

- Does the girl want Mho Siemen...?

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

 

[Fred Abse]

On Sat, 19 Jul 2003 18:43:46 +0100, Chuck Harris wrote:

The various scientific societies
went on a spree of naming every little thing after the giants in the
field. Torr

Evangelista Torricelli, the man that invented the mercury barometer, the
(almost) empty space at the top of which is still called the "Torricellian
Vacuum"

Voltair

Count Alessandro _Volta_, he of "Volta's Pile", the first primary cell.


--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[Tim Williams]

<ehsjr@bellatlantic.net> wrote in message
news:3F1A26C0.B4BDC4C5@bellatlantic.net...

and pass the thing off as an experimental DMM that uses
leds instead of leads -

No no no no no... you've got it all wrong... L - E - D. Not le[a]d.
;-p

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

 

[Bob Masta]

On Sun, 20 Jul 2003 08:50:43 +1000, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:

I would think the most sensible pronunciation would be "giga" as this
prefix is derived from the Greek word, "gigas", meaning "giant".

How do the Greeks pronounce "gigas"? The "jig-a" pronounciation
for giga seems to be in more-or-less in keeping with "gigantic".

Are there any hard-"g" English words with the "giant" meaning?

Not that anything is going to change common usage! ;-)



Bob Masta
tech(AT)daqarta(DOT)com

D A Q A R T A
Data AcQuisition And Real-Time Analysis
Shareware from Interstellar Research
www.daqarta.com

 

[Ratch]

"Watson A.Name - 'Watt Sun'" <alondra101@hotmail.com> wrote in message
news:MPG.1983fbedc6bfe38e989ad7@news.inreach.net...

In article <pRdSa.85516$sY2.38332@rwcrnsc51.ops.asp.att.net>,
Watchit@Comcast.net mentioned...

"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in message
news:3f1963bf$0$28893$1b62eedf@news.euronet.nl...
"Ratch" <Watchit@Comcast.net> schreef in bericht
news:xscSa.97708$Ph3.10866@sccrnsc04...

"Chuck Harris" <cfharris@erols.com> wrote in message
news:bfbfqe$1jt$1@bob.news.rcn.net...

If you ask engineers what is Ohm's law, they will say E = iR,

Only because they learned it that way. If you explained the
misnomer,
then what would they say?

...they'd say you're a pain in the butt. You belong to the same
category
as the ones that always have to say that RS232 is about voltage levels
and has nothing to do with serial ports. Strictly that is correct, but
at the the same time the *entire* world uses the term when referring
to typical serial ports such as COM1 and COM2 on your PC.

And you would rather blame the messenger than appreciate the
message.

E = I * R. Ohm's Law. Always has been, and always will be.

You are in denial. Ratch

And you really are turning into a pain in the butt. At least you're
on topic.

I am just defending my position.

It kind of reminds me of all the spam artlcies in the newsmedia.
They're arguing about the definition of spam, as the whole world is
drowning in it!

No one has to read'em.

There's so much bickering going on, that one would think that no one
understands the problem. I wouldn't be surprised if the lawmakers did
the same thing they've done the last few years: skip it for now and
worry about it later.

Everyone understands the problem, but no one really knows of a
solution, or has the authority to implement it, or has the will and energy
to follow through on what should be done. Ratch

 

[Chuck Harris]

Ratch wrote:

Every solid had a property called resistivity. Resistance is determined by
the resistivity, the shape of the solid, and the
placement of the two measurement leads into the solid.

Prof Serway says the same thing about resistance/resistivity as L&M, except
Serway does not call the formula E=rho*J Ohm's law. Instead Serway says
that if the resistivity (rho) is constant at any electric field (E), then
the material is ohmic. That means that E and J are linearly proportionate to

The equation:

E = rho * j

says that for a constant rho, E is proportional to j. Serway is just
putting the equation to words.

each other. How does L&M define an ohmic material? Ratch

L&M say that, "Materials that obey Ohm's Law are usually called ohmic
conductors. This relation (Ohm's law) 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."

He then goes on to derive E = R * I from E = rho * j.

If you define R = rho * L/A, (R = rho * length/crossectional area)

and realize that V = |E| * L, (V = electric field strength * length)

you get:

V = rho * (L/A) * I => V = R * I, Ohm's law.

-Chuck

 

[Ratch]

"Chuck Harris" <cfharris@erols.com> wrote in message
news:bfe7br$j00$1@bob.news.rcn.net...

Ratch wrote:

Every solid had a property called resistivity. Resistance is determined
by
the resistivity, the shape of the solid, and the
placement of the two measurement leads into the solid.

Prof Serway says the same thing about resistance/resistivity as L&M,
except
Serway does not call the formula E=rho*J Ohm's law. Instead Serway
says
that if the resistivity (rho) is constant at any electric field (E),
then
the material is ohmic. That means that E and J are linearly
proportionate to

The equation:

E = rho * j

says that for a constant rho, E is proportional to j. Serway is just
putting the equation to words.

Serway also writes the equation which I did not quote, with the
stipulation that E and J are linearly proportionate.

each other. How does L&M define an ohmic material? Ratch

L&M say that, "Materials that obey Ohm's Law are usually called ohmic
conductors. This relation (Ohm's law) 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."

He then goes on to derive E = R * I from E = rho * j.

If you define R = rho * L/A, (R = rho * length/crossectional area)

and realize that V = |E| * L, (V = electric field strength * length)

you get:

V = rho * (L/A) * I => V = R * I, Ohm's law.

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