Re: Magnitude of feet-scuffing voltage?

[Karl Trappe <trappe@PHYSICS.UTEXAS.EDU>]

I think the static voltage misconception is discussed in Aaron's book on
teaching introductory physics.  I recall that the problem is reversed, ie,
that students don't think a "battery" or "power supply" will supply the
charge (voltage) of static machines, like Van de Graaff's.  To dispell
this, one does the Q=CV with variable separation parallel plate Capacitor,
but substitutes HV power supplies for static charge machines to supply the
charge (voltage).  Alternately, one uses a power supply to "charge" an
electroscope, to show that there is no difference in the *voltage* from
different sources.

Regarding the humidity leaking charge explanation:  What is the accepted
mechanism?   I know my electrostatics demos don't work when the humidity is
high, so I am guilty of saying that the charge leaks off....Karl

> On Sat, 23 Jan 1999, William Beaty wrote:
>
> > 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.
>
> Have others here encountered this misconception before?  I was aware of
> it, but never wrote it down, and it does not appear on my website.
>
> Perhaps a good question for a misconception-screening exam would read like
> this:  What is the expected voltage range for "static electricity."  If
> you rub a balloon on your head and pull it away, the potential difference
> between the balloon and your head could be: 0 volts, 10 volts, 100 volts,
> 100,000 volts
>
>
> Another unlisted misconception:  humid weather makes the air become damp
> and conductive, and so imbalanced charges will rapidly vanish as they leak
> through the air and to the earth.
>
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> William J. Beaty                                  SCIENCE HOBBYIST website
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Dr. Karl I. Trappe                              Desk Phone:  (512) 471-4152
Physics Dept, Mail Stop C-1600                  Demo Office: (512) 471-5411
The University of Texas at Austin               Home Phone:  (512) 264-1616
Austin, Texas 78712-1081