Zero Ohms = Mathematically Incorrect

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

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.

By "pole", you mean infinity?

So the term "zero resistance" is flawed?

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

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

"Radium"

** 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

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

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.

KISS, nowaddumsayin? Or not?

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

Ah. Where to begin. . 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.

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).

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

If you are really asking an intelligent question and not just trolling then the answer is that ohms law is only an idealization of a physical property. It is similar to how all laws of physics are quite simple mathematically but when you get right down to it they are only approximations. In fact mathematics explains it perfectly but the physics its quite different. It is impossible to have infinite voltage or infinite current.

If, say, you do have a conductor of zero resistance then the fact is that one you put a voltage source that, lets suppose farther, could supply infinite amps then the conductor itself would be destoryed before the current ever got "close" to infinity(i.e., it would be finite). The point being that ohms law fails at these conditions.

Now, we can farther suppose that we have a conductor that can handle an infinite number of amps.... then ohms law says mathematically that if we put a voltage across it then the amps is A = V/R.

Here we can get infinite current by having zero resistance or infinite voltage. Theres surely no problem with infinite voltage if we can do infinite current.

The fact of the matter is that in reality we cannot have such things as zero resistance(even in superconductors), infinite voltage or infinite current... and it only takes one of these to fail for every one to be false too. i.e., if you can't have zero resistance then the others can't old... if you can't have infinite voltage then you cannot supply infinite current or have 0 resistance(because you could then use a current source to drop an infinite voltage across the resistance).

And if you want to get right down to it you will realize that pretty much all these concepts stem from the conservation of energy... and this is one of the reasons why what happens in reality isn't exactly the same as what ohms law says.

Try to get it in your head and infinite doesn't exist in the real world and you might do some good... this has nothing to do with mathematics but with reality. About the closest you might get is saying that the universe is infinite in extent but then I'd ask to prove it and as of yet no one has been able to.

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.

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.

I can prove it, but it will take an infinite amount of time.

Please wait for me to get back to you. :-)

-Mike

Sure... if you can live that long and I have to wait on you then that means I can live that long too?

"Chris" wrote in news:1155783742.710847.146250 @i42g2000cwa.googlegroups.com:

*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

--
As you stated:

          E
     I = ---
          R

so, for any value of E, as R goes to zero I will go to infinity.

"John Fields Autistic "

** Rainman where are you ?????

....... Phil

Inductance. I=V/Z, and Z = R + iwL