Re: Electrolysing Steam
From: Don Lancaster (don_at_tinaja.com)
Date: 10/23/04
- Next message: Don Lancaster: "Re: Can hydrogen deliver?"
- Previous message: Don Lancaster: "Re: Electrolysing Steam"
- In reply to: Don W.: "Re: Electrolysing Steam"
- Next in thread: Hatunen: "Re: Electrolysing Steam"
- Reply: Hatunen: "Re: Electrolysing Steam"
- Messages sorted by: [ date ] [ thread ]
Date: Sat, 23 Oct 2004 07:45:13 -0700
"Don W." wrote:
>
> "Bill Ward" <bwardREMOVE@ix.netcom.com> wrote in message
> news:4179ea0c.51713012@localhost...
> > On Fri, 22 Oct 2004 21:10:44 -0700, "Don W."
> > <dNOSPAMwiddersAThotmail.com> wrote:
> >
> > >"Franz Heymann" <notfranz.heymann@btopenworld.com> wrote
> > >in message news:clcie8$nh2$3@titan.btinternet.com...
> > >>
> > >> "Don W." <dNOSPAMwiddersAThotmail.com> wrote
> > >> in message news:C8KdneiLlbrOBuTcRVn-2w@comcast.com...
> > >>
> <snip>
> > >As I wrote, that was a bit of silliness because I never heard of a
> > >"non-ohmic" conductor and the statement sounds funny (errr, to
> > >ME it sounds funny.)
> > >
> > >In what way is Ohm's law broken? I can't think of an instance
> > >where current does not equal the difference in potential divided
> > >by the resistance across which the difference is measured (with
> > >the possible exception of a superconductor.) The resistance of
> > >ionized gas can be computed by measuring the voltage across
> > >the discharge tube and dividing by the current through the tube.
> > >Right?
> > >
> > >I'm not saying that you invented the term "non-ohmic", but I don't
> > >understand your explanation. As a gas ionizes, its resistance to
> > >the flow of electrical current drops and current flows.
> > >
> > >Don W.
> > >
> > Don, Ohm's law is only an approximation to an ideal, not
> > exact like power = volts * current. You can't independently
> > measure resistance without a current, AFAIK, Determining the
> > "resistance" of a gas tube is really measuring the current
> > and voltage, then deriving a fictitious (but useful)
> > quantity. The current-voltage curve is the only directly
> > measurable data.
> >
> > All resistors are non-linear to some degree, although some
> > (eg Pt) come very close at low current density.
> >
> > Gas tubes usually show a negative dynamic "resistance" when
> > they fire, since the current increases while the voltage
> > drops.
> >
> > People still use the terms static and dynamic resistance for
> > convenience, but it's important to keep in the back of your
> > mind that it's actually the current-voltage curve that
> > counts.
> >
> >
> > Regards,
> >
> > Bill Ward
>
> We've strayed more than a tad off topic, but I'm always eager to learn and
> my respect and admiration for you and Franz and Vaughn compels me to
> determine what I'm missing here. I generally think of Ohm's Law as static
> in nature (no delta T's or integrals over time.) Ohm's Law doesn't say
> that resistance can't change -- only that current changes in inverse
> proportion. Is there another term for 'dynamic "resistance"'? When gas
> tubes fire, resistance changes; does the resistance ever become negative?
> Is there ever a point in time that resistance does not equal voltage
> divided by current?
>
> Is Ohm's Law an approximation, or is the approximation in our ability to
> accurately measure? How does a 'Law' differ from an observation?
>
> Don W.
Ohm's Law in normal usage assumes a constant resistance value.
If the resistance is time or current varying, then considerably more
complex differential math is involved.
Ohm's Law is thus normally a gross everyday oversimplification for
students and technicians.
And is strictly true ONLY in its differential form.
The additional Power Series approximation terms are neglected when and
where appropriate.
-- Many thanks, Don Lancaster Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 voice: (928)428-4073 email: don@tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
- Next message: Don Lancaster: "Re: Can hydrogen deliver?"
- Previous message: Don Lancaster: "Re: Electrolysing Steam"
- In reply to: Don W.: "Re: Electrolysing Steam"
- Next in thread: Hatunen: "Re: Electrolysing Steam"
- Reply: Hatunen: "Re: Electrolysing Steam"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
