Re: Dissectable Capacitor

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

Brian wrote:
...........

> ...... Measure two PDs. That was the idea, at least. I thought that
> a DVM and some 0.1 microfarad caps would do the trick - but the
> digital voltmeter's input resistance is a modest 10 megohms, so
> even 2 microfarad caps discharge too fast.   ..........

Those who have voltmeter probes from Vernier or Pasco (to be
used with an interface to a computer) should be aware that their
input resistance is close to 4 giga-ohms. The old probes were
for up to 6 volts but the new, if I am correct, will hold up to 9
or 10 V (?). Ideal for the kind of experiment described by Brian.
A "student electrometer" from Pasco has the same very high R
and can measure up to 100 V (or is it more now?).

Two or three years ago, using the Vernier probe, I was surprised
to see an electrolytic capacitor to recharge itself after being
discharged. No dissecting of anything in that case. Leigh said
this is a well known effect for all capacitors. Only later did I read
about Faraday's investigation of the charge recovery effect.

By the way, I am missing Leigh.
Ludwik Kowalski