# Zero Ohms = Mathematically Incorrect

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Hi:

If a conductor has zero resistance, then what is the amperage of a
current flowing though it?

Amperage = voltage/resistance

If the resistance is zero, then the amperage is something that math
cannot explain. Anything divided by zero is an "error" when calculated.

How to solve this puzzle?

Thanks,

Re: Zero Ohms = Mathematically Incorrect

On 16 Aug 2006 19:39:29 -0700, in message

Your assertion is incorrect.  Anything divided by zero is a "pole" when
calculated.

Very simple.  The resistance isn't zero in a conductor.  Just in case any
of the children watching were wondering.

Please do try a little harder with your next pitch.  The score is getting
out of hand, and mercy rules may soon apply.

Re: Zero Ohms = Mathematically Incorrect

Alan B wrote:

By "pole", you mean infinity?

So the term "zero resistance" is flawed?

Re: Zero Ohms = Mathematically Incorrect

On 16 Aug 2006 19:53:31 -0700, in message

No, I mean "pole."  The definition of this is beyond the scope of the
group.  Understanding poles requires a knowledge of the Calculus.

Well, yes, if you mean to apply the term to the calculation of values in
the solving of a circuit.  In that case, then the phrase is flawed in the
respect that it is correct to say that the resistance *approaches* zero,
and so may be ignored in the solving, such ignorance being indicated by
insertion of the value, zero, for the conductor bits.

Re: Zero Ohms = Mathematically Incorrect

You should think like this:voltage= Amperage * resistance
If a conductor has zero resistance, there will be zero voltage between
its two ends,no matter how much Amperage.

Re: Zero Ohms = Mathematically Incorrect

On 16 Aug 2006 19:53:43 -0700, in message

Ah.  Where to begin.  <taps keyboard>.  Well, let's keep it simple.  There
is no such thing as zero resistance in a conductor.  When solving a
circuit, we may ignore the impedance in the conductors if we are assured
that their actual electrical properties are of no significance to the
circuit.  Thus, when solving for DC, it is acceptable to plug in the value
of "zero" for both voltage and resistance for all the conductor bits,
because their effect is insignificant.

Re: Zero Ohms = Mathematically Incorrect

On Wed, 16 Aug 2006 20:19:00 -0700, Alan B

Quit that annoying tapping and google "superconductor." Current has
been experimentally circulated in superconductive rings for years with
no indication of losses.

John

Re: Zero Ohms = Mathematically Incorrect

On Thu, 17 Aug 2006 16:54:29 -0700, in message

You missed this bit: "Well, let's keep it simple."  Since I don't have an
absolute-zero chamber in my workshop, I thought I'd leave superconductors
out of the picture.  Zat okay?

Re: Zero Ohms = Mathematically Incorrect

On Thu, 17 Aug 2006 18:12:24 -0700, Alan B

Sure, but it avoids addressing the "math problem", which actually
doesn't exist.

John

Re: Zero Ohms = Mathematically Incorrect

On Thu, 17 Aug 2006 20:54:27 -0700, in message

Pretty soon you're likely to say something specific, but I'm not holding my
breath.

Re: Zero Ohms = Mathematically Incorrect

Alan B wrote:

Short circuit current would be limited by the power source internal
resistance..wouldn't it???

Re: Zero Ohms = Mathematically Incorrect

The resistance of a super conductor is zero. The voltage drop is also zero
so 0/0 is still mathematically correct. A current once started in a zero
resistance loop will continue indefinitely without loss and without decay.
Such a thing does exist it's not science fiction.
Bob

Re: Zero Ohms = Mathematically Incorrect

Hi, R.  In practice, no conductor has exactly zero ohms.  There's
always some resistance.

Any voltage source is also imperfect, and has internal resistance to
"infinite" current.

If you place a copper busbar across the terminals of a fully charged
car battery (don't -- it will explode and give you an acid bath), you
will have hundreds or possibly even a couple thousand amps flowing, but
not an infinite number of amps.  Short circuit current always is
finite.

Some of your difficulties might be cleared up by pulling a basic
electronics book from the library and glancing through it.

Good luck
Chris

Re: Zero Ohms = Mathematically Incorrect

*snip*

(jokingly)
Yeah, but then /I/ would have to do the same!  Let me learn from his
ignorance!!!

Puckdropper
--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm

Re: Zero Ohms = Mathematically Incorrect

** What you measure with an amp meter.

** Only where there  IS a defined resistance with a defined voltage drop.

Otherwise:

Amperage =  the flow of electrons in Coulombs per second.

1 amp  =  6.24 exp18  electrons per second.

**  BOLLOCKS.

**  Get your basic definitions right.

........  Phil

Re: Zero Ohms = Mathematically Incorrect

Assuming an ideal zero-ohm conductor...

It depends on the other resistances in the circuit.

If you had an ideal voltage source, you'd have infinite current.
However, neither ideal zero ohm resistors nor ideal voltage sources
exist in nature (er, excepting superconductors, maybe).  What you
actually end up with is a very high current, limited by (for example)
the battery's internal resistance, tiny wire resistance, etc.

If you had an ideal zero ohm conductor in an otherwise normal circuit,
you end up with zero volts across it.  The other components have all
the voltage across them, and they limit current.

Even if you just shorted a battery, the battery itself has an internal
resistance, which limits the amount of current it can push.  At its
limit, you have a huge amount of current through the conductor, and a
tiny (for real conductors) or zero (for ideal zero ohm conductors)
voltage drop across the conductor.

In this case, you're using the wrong equation anyway.  The amperage is
limited by the battery, so you want the V = I * R equation.  R is
zero, so no value of I (short of infinity) causes a non-zero voltage
drop across the ideal conductor.

Multiplying by zero is mathematically well-defined.  What you can't do
is, given a zero ohm conductor and non-zero amps, determine how much
voltage had been applied.  All you can tell is that it's non-zero,
unless you allow for pre-existing currents (like in a superconducting
loop).

Re: Zero Ohms = Mathematically Incorrect

Yes, but E=IR, so if you have no resistance (R) then the voltage  (E) =
zero and the current (I) is undefined since I=E/R and if E and R are
both zero,  the current (I) can be a very large number, since 0/0 =
infinity. So what is the current in that case?

Another thought is the current and voltage in a LC tank circuit. If the
current reaches a peak at the same time the voltage goes to zero, and
visa versa, what is the current in the LC circuit when the voltage is
zero?

-Bill

Re: Zero Ohms = Mathematically Incorrect

To work with circuits like this, you have to use complex numbers for
volts, current, and "resistance".  That lets you have sinusoidal
voltages and currents that are out of phase with each other, and still
be able to do the math sanely.

In your example, the peak current depends on the peak voltage, and the
L and C values.  If the tank is driven, it also depends on the
frequency of the driving source.

Re: Zero Ohms = Mathematically Incorrect

Isn't it still ohm's law?. For a parallel LC circuit, the reactance of
a super conducting 1 Henry inductor at 1 Hertz will be XL= WL or 6.28
ohms and therefore the peak voltage across the parallel LC circuit will
be 6.28 volts when the peak current is 1 amp, just not at the same
time?

Something like that?

-Bill

Re: Zero Ohms = Mathematically Incorrect

Don't get hung up on the math.  Think it through.
Current is defined to be the movement of charge
measured in Coulombs per second passing through
a given cross sectional area.