Re: OT: volt and current (ALSA sound recording frustration)
On Fri, Nov 28, 2008 at 04:13:21PM -0500, Andrew Reid wrote:
> On Friday 28 November 2008 14:10, lee wrote:
> > Is it even possible to measure a mere potential?
>
> You mean, in principle? Of course.
>
> Put your two wires of unknown potential difference at
> opposite ends of an evacuated tube. Arrange the geometry
> so that the electric field between them is linear in space.
> You can do this by hooking them up to big plates and putting
> the plates close enough together, making basically a
> vacuum capacitor.
>
> Then, shoot charged particles into the space between
> the electrodes. From the way they deflect, and their
> charge-to-mass ratio, you can deduce the electric field
> strength, and from that, the potential difference between
> the electrodes giving rise to the field.
>
> Alternate method: Place a piezoelectric crystal of
> known characteristics in the gap, and measure the
> change in shape. From this, you can deduce the degree
> of polarization, and thus the externally-applied field,
> and from that, again, the voltage difference between
> the electrodes.
It takes energy to defect particles or to change the shape of a
crystal, doesn't it? You would be observing/measuring effects and
*deduce* that there is a potential, but that is different from
observing/measuring the potential itself, isn't it?
--
"Don't let them, daddy. Don't let the stars run down."
http://adin.dyndns.org/adin/TheLastQ.htm
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