Date:         Thu, 13 Nov 2003 22:05:48 -0600
Reply-To:     tom ring <taring@TARING.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         tom ring <taring@TARING.ORG>
Organization: Tippen Ringware
Subject:      Re: Fwd: RE: "Green" solar battery charger
In-Reply-To:  <vanagon%2003111322305962@GERRY.VANAGON.COM>
Content-type: text/plain; charset=US-ASCII

Uh, sorry, Ohm's law works.  And it is a law.  Just like Kirchoff's.  No
qualifications at any reasonable level of detail until you get to the quantum
mechanical level, and that's not applicable to anything this group would
experience.  AMD and Intel chip engineers maybe are getting near there, but not
us.

And Newton's work fine until you speed things up, a lot.

tom

On 13 Nov 2003 at 22:27, Daniel L. Katz wrote:

> jack:
>
> ohm's law really isn't a law, in the sense that newton's laws, for
> example, are physical laws. that is, if motion is studied in finer and
> finer detail, the limit is complete agreement with newton's laws. on the
> other hand, if current in a resistor is studied with increasing detail,
> the picture gets more and more complicated, with all kinds of empirically
> determined parameters, and so on.
>
> dlk
>
> On Thu, 13 Nov 2003 19:05:38 -0800, Jack <john.cook58@VERIZON.NET> wrote:
>
> >re: "... ohm's law implies that a current of 12 V/300 Ohm = 0.04 A
> >will flow ..."
> >
> >No!  It doesn't "imply".  It's the LAW!
> >
> >Sorry.  Couldn't resist.
> >
> >//Jack
> >
> >
> >On 13 Nov 2003, at 16:59, Daniel L. Katz wrote:
> >
> >> list:
> >>
> >> kindly note that current and voltage are not independent, and that 100
> mA
> >> through the heart for 1 s would probably be fatal.
> >>
> >> in the simplest cases, current and voltage are related fairly precisely
> >> through ohm's law:
> >>
> >> I = V/R
> >>
> >> where I = current and V = potential difference across R. for example,
> if 12
> >> volts is applied across a 300 ohm 1 W resistor, ohm's law implies that a
> >> current of 12 V/300 Ohm = 0.04 A will flow through the resistor. it
> makes no
> >> difference whether we say the voltage is 12 V on one side of the
> resistor and
> >> 0 volts on the other, or 1,000,012 volts on one side and 1,000,000
> volts on
> >> the other, we get the same 12 V potential difference across the
> resistor, and
> >> the same amount of current, 0.04 A, will flow. in this case, the power
> >> developed by the resistor would be 0.48 watts, within its 1 W power
> rating.
> >> now, what if we substitute a 30 ohm 1 W resistor instead? well ohms law
> would
> >> predict a 0.4 A curren and heat produced at the rate of 4.8 W, nearly 5
> times
> >> the power rating of the resistor; in this case, ohm's law does its job
> in so
> >> far as letting us know that the resitor would fry, but the resistor
> itself
> >> would change value significantly as it burned up.
> >>
> >> dlk
> >>
> >>
> >>
> >> >The charge LED flashes fine even in pretty low light, but it's only
> >> >indicating that there's voltage present... however there's nearly no
> >> >current, and it's current, not voltage, which will charge a
> >> >battery... or an electrocution! (a 100mA current of 1,000,000V will
> >> >not even be felt).
>


------
Tom Ring K0TAR, ex-WA2PHW  EN34hx
85 Westphalia GL Albert
96 Jetta GL The Intimidator
taring@taring.org

"It is better to go into a turn slow, and come out fast, than to go into a turn fast
and come out dead." Stirling Moss