----------------------------
wrote in message
...
Benj wrote:
On Sep 6, 1:55?am, wrote:
Benj wrote:

I do know enough to keep from being totally wrong unless I INTEND to
be
totally wrong! :-)

Then you should know enough to go to a reference such as NIST where
you will find that resistance is *DEFINED* to be E/I.

http://physics.nist.gov/cuu/Units/units.html

Pay close attention to the 11th item in Table 3.

Jimp, Jimp, Jimp!
I really don't understand people with a secret desire to be PROVED to
be ignorant in a world-wide public forum.

We are talking here about OHM'S LAW. We are not talking about the
definition of "resistance".

So please allow me to quote from the college freshman physics text
(which of course means that you will have no acquaintance with it)
Halliday & Resnick Vol II p. 665.

"We stress that the relationship V=IR is NOT a statement of Ohm's law.
Strictly, in the light of modern standardizing procedures, it is a
defining equation for V. ONLY IF THE V-I CURVE IS LINEAR (that is R is
a constant) is the conductor said to obey Ohm's Law. We express Ohm's
Law in terms of microscopic quantities by saying that the law is
obeyed if p (rho) in p=E/j is independent of E. Ohm's Law is a
specific property of certain materials and not a general law of
electromagnetism."

You're a moron. QED. OK?

I'm sorry I had to use an actual physics textbook to make the point
rather than Wikipedia, but I hope you get the idea. Are you now
satisfied that you just made a fool of yourself in front of the entire
world?

Take your arguement to ISO, SI, NIST, etc. and see how far you get.

His argument would be accepted- there is no contradiction involved. He is
talking about the specific relationship which is Ohm's Law while NIST etc
are defining the unit called an Ohm. Saying R=E/I is defining resistance but
it is not "Ohm's Law" unless R is constant. That is Benj's point (and one
that is too often missed by those who should know better- hence what
Halliday and Resnick as well as other reputable texts emphasise).
--

Don Kelly
remove the X to answer



--
Jim Pennino

Remove .spam.sux to reply.

Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:

----------------------------
wrote in message
...
Benj wrote:

But do not be misled by the clowns here and elsewhere who pretend that
ALL substances follow Ohm's law. They don't. Even copper, which is
more or less a standard material for electrical wires, is rather
unstable with regard to Ohm's law. When resistors are made from coils
of wire, copper is NOT the wire used for this reason. Other conductors
(like say plasmas) are FAR from following Ohm's Law.

EVERYTHING follows Ohm's law at the macro, or bulk if you like that
term better, level.

The reason copper wire is not used to make wire wound resistors is the
resistivity of copper is so low it would take huge amounts of wire
to make a resistor which could be made with a far fewer number of
turns of a wire with more resistivity.

--
Jim Pennino

Remove .spam.sux to reply.

Jim - you know better. Ohm's law simply reflects a linear relationship
which holds within limits. If you can represent the relationship between
voltage and current as a linear one (i.e. R constant) then the material
is
ohmic. Otherwise it is not and Ohm's Law isn't worth a damn (which Ohm
recognized). Even for good conductors such as copper- there are limits to
this relationship. Strictly speaking Ohm's Law is restricted to the
linear
case and i=v/R is NOT Ohm's law except when R is constant.

jimp is right.

Look up Ohms Law as Ohm defined it.

It appears that you have looked at the Wiki reference
acceptingly-including
its error in the last part. In the macroscopic level, does a diode follow
Ohm's Law- definitely not but for a small signal situation far from the
origin of the V vs i characteristic, it does (approximately).


Don Kelly
remove the X to answer

By that logic nothing ever follows Ohm's law since there is nothing
with a constant, fixed resistance though the change may not be
measureable.

However, the General Conference on Weights and Measures held by the
International Bureau of Weights and Measures, the organization chartered
with the maintenance of the International System of Unit (SI), defines the
ohm as a derived unit equal to E/I.

The SI does not arm wave about linear, non-linear, diodes, temperature
coefficients, or anything else, they simply define R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.

That is the definition of the UNIT "ohm" I have no argument there.

It is NOT the definition of Ohm's "Law" which is the linear relationship
that he discovered (for the materials he tested and over specific ranges of
operation - hence the term "ohmic material". In other words, there is a
constant of proportionality between Voltage and current and this is called
"R" rather than "K" or "Bob" The only variable constant of proportionality
is "De Bouguerre's Factor" which fits whatever is needed to make the numbers
right.

Ohm's Law is meaningless for non-linear elements but very useful for linear
elements.
Certainly for a circuit with a linear and non-linear part such that
V=2*I +0.5I^2 you could then write an equivalent R' =0.5I (in ohms) but
that would be useless in trying to find the current for a given voltage as
R'I is still 0.5I^2.

In addition, for circuits with non-linear elements, the nice circuit
techniques that we have all used are rat**** except for Kirchoffs Laws as
they all depend on linearity. So, we go to either non-linear analysis which
is fine in simple cases but a bugger in others or go to small signal
analysis which assumes linearity in a localized region.

OK, so in spite of the fact that the definition of the resistance of
an object in ohms is the voltage applied across the object in volts
divided by the current through the object in amps with the only condition
being that the object can not contain either voltage or current sources,
you are going to keep on arm waving.

Fine.

--
Jim Pennino

Remove .spam.sux to reply.

----------------------------
wrote in message
...
In sci.physics.electromag, Salmon Egg wrote:

Are you saying that low voltage electricity travels at the same
velocity
as high voltage electicity?

That is a fact!

OK.

Say you have a souce of power (say, a hydro-powered generator) and you
want to transmit that power to a remote location. Let's say that the
generator is designed to work properly at 600 volts AC.

You could transmit all that power at 600v through thick wires. Or you
could tranform the electricity to 23,000v and use much thinner wires.

Same amount of power (ignoring the relatively minor transformation
losses), but thinner wires can handle it without adverse consequences.

At a physical level, what is the difference? How can so much power get
crammed through a thin wire per interval of time?

I guessed that the electrons are moving faster, but you say that is
incorrect. So what is the answer?

Are the electrons packed more densely at higher voltage?

--
The whole problem with the world is that fools and fanatics are always so
certain of themselves, but wiser people so full of doubts.
-- Bertrand Russel

==========
You are apparently confusing power with current.
Power is the product of voltage and current.

In any case the power that the generator provides is that required by the
load - the generator doesn't transmit anything except what the load needs
(plus losses).
So, if a load draws 1000KW at 600V, the current required ( single phase at
unity power factor) is 1667A which would require a very large conductor and
even at that, the voltage drop along the line would be large (as would be
the losses). If the load draws 1000KW at 60000V then the current would
be17A which could be handled by a smaller conductor, with lower voltage
drops and less less losses and overall the transmission cost would be
lower.

--

Don Kelly
remove the X to answer

wrote ...
In sci.physics.electromag, Salmon Egg wrote:


I guessed that the electrons are moving faster, but you say that is
incorrect. So what is the answer?

Are the electrons packed more densely at higher voltage?

You have the two possibilities: The hydraulic analogy and the gas analogy.
In the first the electrons must move faster. In the second the electrons are
packed more densely at higher voltage.
The hydraulic analogy is for school-children (piece to teach). For adults is
the gas analogy.
S*

----------------------------
wrote in message
...
Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:

----------------------------
wrote in message
...
Benj wrote:

But do not be misled by the clowns here and elsewhere who pretend
that
ALL substances follow Ohm's law. They don't. Even copper, which is
more or less a standard material for electrical wires, is rather
unstable with regard to Ohm's law. When resistors are made from coils
of wire, copper is NOT the wire used for this reason. Other
conductors
(like say plasmas) are FAR from following Ohm's Law.

EVERYTHING follows Ohm's law at the macro, or bulk if you like that
term better, level.

The reason copper wire is not used to make wire wound resistors is the
resistivity of copper is so low it would take huge amounts of wire
to make a resistor which could be made with a far fewer number of
turns of a wire with more resistivity.

--
Jim Pennino

Remove .spam.sux to reply.

Jim - you know better. Ohm's law simply reflects a linear
relationship
which holds within limits. If you can represent the relationship
between
voltage and current as a linear one (i.e. R constant) then the
material
is
ohmic. Otherwise it is not and Ohm's Law isn't worth a damn (which Ohm
recognized). Even for good conductors such as copper- there are limits
to
this relationship. Strictly speaking Ohm's Law is restricted to the
linear
case and i=v/R is NOT Ohm's law except when R is constant.

jimp is right.

Look up Ohms Law as Ohm defined it.

It appears that you have looked at the Wiki reference
acceptingly-including
its error in the last part. In the macroscopic level, does a diode
follow
Ohm's Law- definitely not but for a small signal situation far from the
origin of the V vs i characteristic, it does (approximately).


Don Kelly
remove the X to answer

By that logic nothing ever follows Ohm's law since there is nothing
with a constant, fixed resistance though the change may not be
measureable.

However, the General Conference on Weights and Measures held by the
International Bureau of Weights and Measures, the organization chartered
with the maintenance of the International System of Unit (SI), defines
the
ohm as a derived unit equal to E/I.

The SI does not arm wave about linear, non-linear, diodes, temperature
coefficients, or anything else, they simply define R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.

That is the definition of the UNIT "ohm" I have no argument there.

It is NOT the definition of Ohm's "Law" which is the linear relationship
that he discovered (for the materials he tested and over specific ranges
of
operation - hence the term "ohmic material". In other words, there is a
constant of proportionality between Voltage and current and this is
called
"R" rather than "K" or "Bob" The only variable constant of
proportionality
is "De Bouguerre's Factor" which fits whatever is needed to make the
numbers
right.

Ohm's Law is meaningless for non-linear elements but very useful for
linear
elements.
Certainly for a circuit with a linear and non-linear part such that
V=2*I +0.5I^2 you could then write an equivalent R' =0.5I (in ohms) but
that would be useless in trying to find the current for a given voltage
as
R'I is still 0.5I^2.

In addition, for circuits with non-linear elements, the nice circuit
techniques that we have all used are rat**** except for Kirchoffs Laws as
they all depend on linearity. So, we go to either non-linear analysis
which
is fine in simple cases but a bugger in others or go to small signal
analysis which assumes linearity in a localized region.

OK, so in spite of the fact that the definition of the resistance of
an object in ohms is the voltage applied across the object in volts
divided by the current through the object in amps with the only condition
being that the object can not contain either voltage or current sources,
you are going to keep on arm waving.

Fine.

--
Jim Pennino

Remove .spam.sux to reply.
---------
Certainly you can define resistance by R= E/I, and define its unit as the
Ohm.
That is not a problem. A resistance is a resistance even if not constant. I
am not arguing with you regarding that and have no objection to the use of
this relationship (even though it really doesn't do anything useful in the
non-linear case). NIST, etc are doing this.

The problem is that R=E/I ( however useful) is NOT Ohm's Law EXCEPT when R
is constant.
In other words, Ohm's Law is more restrictive than R=E/I even though it
takes the same form. Too often this restriction, which is important, is
ignored.



There has been a decline in some (but mainly the more simplistic sources) of
the on-line literature which omit mention (even though they use it) of the
important factor that is intrinsic to Ohm's Law - a "directly proportional"
relationship between current and voltage or "R is a constant of
proportionality..." as indicated in reputable texts and references. Both of
these terms imply constant R.
I am not trying to redefine "Ohm's Law" but am, just as Halliday & Resnick,
as well as Fitzgerald, etc and others in basic circuits texts pointing out
this fact (even Wikipedia cites the "direct proportionality" relationship ).

NIST etc, are not defining Ohm's Law and I am trying to present the factual
difference between Ohm's Law and R=E/I. This is hardly handwaving.
Sure I am being pedantic because I don't like to see the essential basis
that made it a "Law" (as relationships that were observed tended to be
called) in the first place being ignored.
--

Don Kelly
remove the X to answer

Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:

----------------------------
wrote in message
...
Benj wrote:

But do not be misled by the clowns here and elsewhere who pretend
that
ALL substances follow Ohm's law. They don't. Even copper, which is
more or less a standard material for electrical wires, is rather
unstable with regard to Ohm's law. When resistors are made from coils
of wire, copper is NOT the wire used for this reason. Other
conductors
(like say plasmas) are FAR from following Ohm's Law.

EVERYTHING follows Ohm's law at the macro, or bulk if you like that
term better, level.

The reason copper wire is not used to make wire wound resistors is the
resistivity of copper is so low it would take huge amounts of wire
to make a resistor which could be made with a far fewer number of
turns of a wire with more resistivity.

--
Jim Pennino

Remove .spam.sux to reply.

Jim - you know better. Ohm's law simply reflects a linear
relationship
which holds within limits. If you can represent the relationship
between
voltage and current as a linear one (i.e. R constant) then the
material
is
ohmic. Otherwise it is not and Ohm's Law isn't worth a damn (which Ohm
recognized). Even for good conductors such as copper- there are limits
to
this relationship. Strictly speaking Ohm's Law is restricted to the
linear
case and i=v/R is NOT Ohm's law except when R is constant.

jimp is right.

Look up Ohms Law as Ohm defined it.

It appears that you have looked at the Wiki reference
acceptingly-including
its error in the last part. In the macroscopic level, does a diode
follow
Ohm's Law- definitely not but for a small signal situation far from the
origin of the V vs i characteristic, it does (approximately).


Don Kelly
remove the X to answer

By that logic nothing ever follows Ohm's law since there is nothing
with a constant, fixed resistance though the change may not be
measureable.

However, the General Conference on Weights and Measures held by the
International Bureau of Weights and Measures, the organization chartered
with the maintenance of the International System of Unit (SI), defines
the
ohm as a derived unit equal to E/I.

The SI does not arm wave about linear, non-linear, diodes, temperature
coefficients, or anything else, they simply define R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.

That is the definition of the UNIT "ohm" I have no argument there.

It is NOT the definition of Ohm's "Law" which is the linear relationship
that he discovered (for the materials he tested and over specific ranges
of
operation - hence the term "ohmic material". In other words, there is a
constant of proportionality between Voltage and current and this is
called
"R" rather than "K" or "Bob" The only variable constant of
proportionality
is "De Bouguerre's Factor" which fits whatever is needed to make the
numbers
right.

Ohm's Law is meaningless for non-linear elements but very useful for
linear
elements.
Certainly for a circuit with a linear and non-linear part such that
V=2*I +0.5I^2 you could then write an equivalent R' =0.5I (in ohms) but
that would be useless in trying to find the current for a given voltage
as
R'I is still 0.5I^2.

In addition, for circuits with non-linear elements, the nice circuit
techniques that we have all used are rat**** except for Kirchoffs Laws as
they all depend on linearity. So, we go to either non-linear analysis
which
is fine in simple cases but a bugger in others or go to small signal
analysis which assumes linearity in a localized region.

OK, so in spite of the fact that the definition of the resistance of
an object in ohms is the voltage applied across the object in volts
divided by the current through the object in amps with the only condition
being that the object can not contain either voltage or current sources,
you are going to keep on arm waving.

Fine.

--
Jim Pennino

Remove .spam.sux to reply.
---------
Certainly you can define resistance by R= E/I, and define its unit as the
Ohm.
That is not a problem. A resistance is a resistance even if not constant. I
am not arguing with you regarding that and have no objection to the use of
this relationship (even though it really doesn't do anything useful in the
non-linear case). NIST, etc are doing this.

The problem is that R=E/I ( however useful) is NOT Ohm's Law EXCEPT when R
is constant.
In other words, Ohm's Law is more restrictive than R=E/I even though it
takes the same form. Too often this restriction, which is important, is
ignored.



There has been a decline in some (but mainly the more simplistic sources) of
the on-line literature which omit mention (even though they use it) of the
important factor that is intrinsic to Ohm's Law - a "directly proportional"
relationship between current and voltage or "R is a constant of
proportionality..." as indicated in reputable texts and references. Both of
these terms imply constant R.
I am not trying to redefine "Ohm's Law" but am, just as Halliday & Resnick,
as well as Fitzgerald, etc and others in basic circuits texts pointing out
this fact (even Wikipedia cites the "direct proportionality" relationship ).

NIST etc, are not defining Ohm's Law and I am trying to present the factual
difference between Ohm's Law and R=E/I. This is hardly handwaving.
Sure I am being pedantic because I don't like to see the essential basis
that made it a "Law" (as relationships that were observed tended to be
called) in the first place being ignored.
--

Don Kelly
remove the X to answer

OK, so the bottom line is you don't like the phrase "Ohm's Law" which
says E=IR but are fine with resistance being defined as R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.

On Sep 7, 9:35*pm, wrote:

OK, so the bottom line is you don't like the phrase "Ohm's Law" which
says E=IR but are fine with resistance being defined as R=E/I.

BZZZZZZZTTTT! WRONG!

Ohm's law does NOT "say" E=IR!
Go read the very first sentence of my Halliday and Resnick Quote
again.

sheesh

Benj

Benj wrote:
On Sep 7, 9:35?pm, wrote:

OK, so the bottom line is you don't like the phrase "Ohm's Law" which
says E=IR but are fine with resistance being defined as R=E/I.

BZZZZZZZTTTT! WRONG!

Ohm's law does NOT "say" E=IR!
Go read the very first sentence of my Halliday and Resnick Quote
again.

Your correct, how silly of me when it actually says V=IR.


--
Jim Pennino

Remove .spam.sux to reply.

wrote:
Benj wrote:
On Sep 7, 9:35?pm, wrote:

OK, so the bottom line is you don't like the phrase "Ohm's Law" which
says E=IR but are fine with resistance being defined as R=E/I.

BZZZZZZZTTTT! WRONG!

Ohm's law does NOT "say" E=IR!
Go read the very first sentence of my Halliday and Resnick Quote
again.

Your correct, how silly of me when it actually says V=IR.

Too trite and I tire of this.

The relationship R=E/I is always true for all materials at the macro level
because it is a definition that has one, and only one, condition which is
that the R can not contain any sources.

What Georg Ohm said in 1827 was not R=E/I, but something a bit more
complex.

Feel free to read what he actually wrote:

http://www.mb.fh-nuernberg.de/bib/te...sche_Kette.pdf

The simple fact is that the relationship E=IR is now called Ohm's Law.

Whether the relationship E=IR should or should not be called Ohm's Law
is a semantic and historical arguement, but the fact is that's what it
is called.

And again, the relationship is always true because it is a definition.

Your arguement on what to call this relationship is about as usefull
as arguing acetylsalic acid isn't Aspirin unless it is made by Bayer
because Aspirin is (or was) a Bayer trademark.


--
Jim Pennino

Remove .spam.sux to reply.

----------------------------
wrote in message
...
Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:
----------------------------
wrote in message
...
Don Kelly wrote:

----------------------------
wrote in message
...
Benj wrote:

But do not be misled by the clowns here and elsewhere who pretend
that
ALL substances follow Ohm's law. They don't. Even copper, which is
more or less a standard material for electrical wires, is rather
unstable with regard to Ohm's law. When resistors are made from
coils
of wire, copper is NOT the wire used for this reason. Other
conductors
(like say plasmas) are FAR from following Ohm's Law.

EVERYTHING follows Ohm's law at the macro, or bulk if you like that
term better, level.

The reason copper wire is not used to make wire wound resistors is
the
resistivity of copper is so low it would take huge amounts of wire
to make a resistor which could be made with a far fewer number of
turns of a wire with more resistivity.

--
Jim Pennino

Remove .spam.sux to reply.

Jim - you know better. Ohm's law simply reflects a linear
relationship
which holds within limits. If you can represent the relationship
between
voltage and current as a linear one (i.e. R constant) then the
material
is
ohmic. Otherwise it is not and Ohm's Law isn't worth a damn (which
Ohm
recognized). Even for good conductors such as copper- there are
limits
to
this relationship. Strictly speaking Ohm's Law is restricted to the
linear
case and i=v/R is NOT Ohm's law except when R is constant.

jimp is right.

Look up Ohms Law as Ohm defined it.

It appears that you have looked at the Wiki reference
acceptingly-including
its error in the last part. In the macroscopic level, does a diode
follow
Ohm's Law- definitely not but for a small signal situation far from
the
origin of the V vs i characteristic, it does (approximately).


Don Kelly
remove the X to answer

By that logic nothing ever follows Ohm's law since there is nothing
with a constant, fixed resistance though the change may not be
measureable.

However, the General Conference on Weights and Measures held by the
International Bureau of Weights and Measures, the organization
chartered
with the maintenance of the International System of Unit (SI), defines
the
ohm as a derived unit equal to E/I.

The SI does not arm wave about linear, non-linear, diodes, temperature
coefficients, or anything else, they simply define R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.

That is the definition of the UNIT "ohm" I have no argument there.

It is NOT the definition of Ohm's "Law" which is the linear
relationship
that he discovered (for the materials he tested and over specific
ranges
of
operation - hence the term "ohmic material". In other words, there is a
constant of proportionality between Voltage and current and this is
called
"R" rather than "K" or "Bob" The only variable constant of
proportionality
is "De Bouguerre's Factor" which fits whatever is needed to make the
numbers
right.

Ohm's Law is meaningless for non-linear elements but very useful for
linear
elements.
Certainly for a circuit with a linear and non-linear part such that
V=2*I +0.5I^2 you could then write an equivalent R' =0.5I (in ohms)
but
that would be useless in trying to find the current for a given voltage
as
R'I is still 0.5I^2.

In addition, for circuits with non-linear elements, the nice circuit
techniques that we have all used are rat**** except for Kirchoffs Laws
as
they all depend on linearity. So, we go to either non-linear analysis
which
is fine in simple cases but a bugger in others or go to small signal
analysis which assumes linearity in a localized region.

OK, so in spite of the fact that the definition of the resistance of
an object in ohms is the voltage applied across the object in volts
divided by the current through the object in amps with the only
condition
being that the object can not contain either voltage or current sources,
you are going to keep on arm waving.

Fine.

--
Jim Pennino

Remove .spam.sux to reply.
---------
Certainly you can define resistance by R= E/I, and define its unit as
the
Ohm.
That is not a problem. A resistance is a resistance even if not
constant. I
am not arguing with you regarding that and have no objection to the use
of
this relationship (even though it really doesn't do anything useful in
the
non-linear case). NIST, etc are doing this.

The problem is that R=E/I ( however useful) is NOT Ohm's Law EXCEPT when
R
is constant.
In other words, Ohm's Law is more restrictive than R=E/I even though it
takes the same form. Too often this restriction, which is important, is
ignored.



There has been a decline in some (but mainly the more simplistic sources)
of
the on-line literature which omit mention (even though they use it) of
the
important factor that is intrinsic to Ohm's Law - a "directly
proportional"
relationship between current and voltage or "R is a constant of
proportionality..." as indicated in reputable texts and references. Both
of
these terms imply constant R.
I am not trying to redefine "Ohm's Law" but am, just as Halliday &
Resnick,
as well as Fitzgerald, etc and others in basic circuits texts pointing
out
this fact (even Wikipedia cites the "direct proportionality"
relationship ).

NIST etc, are not defining Ohm's Law and I am trying to present the
factual
difference between Ohm's Law and R=E/I. This is hardly handwaving.
Sure I am being pedantic because I don't like to see the essential basis
that made it a "Law" (as relationships that were observed tended to be
called) in the first place being ignored.
--

Don Kelly
remove the X to answer

OK, so the bottom line is you don't like the phrase "Ohm's Law" which
says E=IR but are fine with resistance being defined as R=E/I.


--
Jim Pennino

Remove .spam.sux to reply.
-------------
Twisting- shame on you.

Ohm's Law is NOT E=IR nor is it R=E/I nor is it I=E/R- in fact none of
these
EXCEPT when R is constant. The definition of Ohm's Law includes this
important factor.
Not my definition but the definition that is accepted world wide.

--

Don Kelly
remove the X to answer