Re: voltages etc.

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

the point is that when the measurement is finally made the current is
essentially zero....now we can argue about what zero means...I suggest
it changes daily with technology.

cheers

On Mon, 3 Mar 2003, Bernard Cleyet wrote:

> I know this is being picky, but:  the current is low, but not zero.  First
> while bringing a potentiometer into balance there is significant flow.
> Second the degree of balance depends on the sensitivity of the null
> detector.  Even if by accident it is "balanced", fluctuations in the test
> voltage and the tested will ensure a current.  (I must be desperate here.)
> Other methods that depend on no connection except by a capacitor (CCD) have
> an initial flow to charge the cap.
>
> bc who used to have an L & N Type K
>
> p.s. I gave up waiting for your (Bob. S.) site to load
>
> p.p.s. The field mill described in the Sci. Am. article I posted. appears to
> be a Kelvin probe.  That article is only one of at least three on this
> subject in the collection.
>
> Bob Sciamanda wrote:
>
> > Recall the potentiometer circuit.  Go to:
> > http://www.plus2physics.com/current_electricity/study_material.asp?chapter
> > =5
> >
> > Bob Sciamanda (W3NLV)
> > Physics, Edinboro Univ of PA (em)
> > trebor@velocity.net
> > http://www.velocity.net/~trebor
> > ----- Original Message -----
> > From: "Bernard Cleyet" <anngeorg@PACBELL.NET>
> > To: <PHYS-L@lists.nau.edu>
> > Sent: Monday, March 03, 2003 2:42 PM
> > Subject: Re: voltages etc.
> >
> > | . . .
> > | BTW, how may one, pray tell,  measure a PD without a current flow?
> > |
> > | bc
> >
> > ---
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Joseph J. Bellina, Jr.               574-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556