Re: Magnitude of feet-scuffing voltage?

[William Beaty <billb@ESKIMO.COM>]

On Fri, 22 Jan 1999, brian whatcott wrote:

> I am probably being needlessly didactic to mention that the leaf
> electroscope was intended to be qualitative, but in some refined versions
> the leaf electrometer was  capable of quantitative indications.

My situation is abnormal: the purpose of the voltmeter is to shatter the
misconceptions of a person who believes that "static electricity" involves
only surface charge, and has nothing to do with high voltage.  (This
misconception is not rare.  It is caused by the teachings of K-12
textbooks where qualitative attraction/repulsion forces are repeatedly
emphasized, but the actual magnitude of the potential between the objects
involved is never mentioned.)

As a consequence, he will assume that an electroscope is simply displaying
the repulsion of charges, and that this proves nothing about the existence
of high voltages.  Mathematical arguments proved useless.  Chains of
reasoning proved useless.  Only a voltmeter can offer proof!   :)

Normally in this situation I would simply give up.  Some levels of
hostile, overconfident ignorance cannot be altered by any amount of
contradictory evidence (and this state is its own punishment!)  However,
if the price is right, I would find an electrostatic voltmeter to be
useful for other applications.

>  One is tempted to propose a DVM chip because of their  exceptionally high
> input impedance around 10^10 ohms. But the nature of the conversion makes
> fleeting signals difficult to register. And a potential divider of 10^10
> ohms and 10^6 ohms is not on everyone's shelf. ( Some ingenuity is needed
> to fashion something of this kind from a slightly conductive plastic film
> or tile...)

Long ago I experimented with tera-ohm resistors made from thin lines of
dilute india ink on plastic.  Seemed to work OK.

>  I recall the frustrations of measuring the geoelectric gradient of abt.
> 120 volts/meter.
>  One might consider an insulated gate field effect transistor ( IGFET) with
> its
> gate driven by such a divider, mounted judiciously on expanded polystyrene
> blocks for its exceptionally high bulk resistance (which material is quite
> capable of blowing most semiconductors from frictional electric effects).
> This igfet component is to be found at the shack.

Yep, I'm looking for the store-bought version of the above, if the price
does not exceed $100 by too much.  If I build it myself, it will be
useless for winning any arguments, because it is common on that forum for
users to do anything rather than to admit a mistake, and to lie in order
to win arguments.  Dishonest people trust nobody.

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William J. Beaty                                  SCIENCE HOBBYIST website
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