Re: Don was saying...
From: Bob Eldred (nsmontassoc_at_yahoo.com)
Date: 01/19/05
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Date: Wed, 19 Jan 2005 08:39:36 -0800
"Peter Lowrie" <peterlowrie@consultant.com> wrote in message
news:7094096.24YjIWB2Pe@xbox.pelnet.net...
> In a discussion in the "try" thread, Don mentioned (paraphrased) that Ohms
> Law (isn't really a law) is not applicable insofar as electrolysis is
> concerned.
>
> Well I thought that something was awry when current measurements to
> electrolysis devices showed, what I thought, were completely anomalous
> results.
>
> Whereas the cell has an impedance measurement of 20,000 Ohms and whereas
> powering it at 2 volts DC resulted in the clamp meter displaying 800 Amps
i
> was left scratching the noggin at this apparent breakage of Ohms law.
>
> One would think that 2v/20000ohms the unit would draw microamps and
clearly
> this is not the case.
>
> Then Don imparted wisdom to the effect, something to do with V I slope and
I
> don't recall this being covered in electronics 101.
>
> The sacred tombe to which I refer for most of my answers is "the art of
> electronics' by Horowitz and Hill {probably known to the Guru} which
drifts
> into discussion on reactive AC circuits but none of the formulae therein
> provide numbers differing from expected calculations for power in an
> inductive circuit or that in a reactive one.
>
> So i am still adrift in this sea of electrolysis anomalies and I'm afraid
my
> pea sized brain is unable to fathom the reasons why, and moreover, what on
> earth the Guru means when he states that Ohms Theory is not applicable
> therein.
>
> Regards
> Peter
People are wrong when they claim that ohms law doesn't work or apply. Ohms
law does apply and has not been repealed, at least yet. The issue is that
the resistance of a cell is nonlinear which means that it exhibits different
resistances at different operating points of voltage and current. At any
given point of current and voltage, ohms law very much does apply. When you
measure the resistance with a simple ohmmeter, you are measuring it at one
point, a point with a very low sense voltage. The resistance is high at this
voltage, the cell is barely in conduction. At a different, higher voltage,
say several volts, the cells conduction increases, the resistance drops and
the current comes on as you have observed. If you had an ohmmeter that
measured at that higher voltage, it would show the appropriate low
resistance. There are many electrical devices that exhibit non- linear
behavior besides electrolytic cells. The common diode comes to mind. There
the resistance is a function of polarity in addition to being nonlinear in
the forward direction. At a few millivolts of forward voltage, most diodes
have a resistance of megohms. This decreases down to an ohm or below as the
voltage exceeds .7 volts. Note that these non-linearities have nothing to do
with reactance as applied to AC circuits with inductors and capacitors.
Don't give up on ohms law quite yet.
Bob
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