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Maybe he wants to compete with Jacques Pépin?
bc
P.s. Also don't wait long after shortening the caps. (dielectric
relaxation) Another wow demo, I first saw demo'd by the NCNAAPT Prez. (heard
about long ago). Rmove the dielectric (after charging), short the plates,
replace the dielectric, and see if any one will volunteer to short it with
their hand.
Jack Uretsky wrote:
> I doubt that 2A actually means what it appears to say!
> Regards,
> Jack
> On Mon, 11 Feb 2002, Ludwik Kowalski wrote:
>
> > In reading my own message I see that one thing was
> > missing. It has been inserted as point 2A below.
> > --------------------------------------------------------------
> >
> > 1) Suppose you want to verify a prediction about the
> > equivalent capacitance of two or more capacitors
> > connected in one way or another. This is easy when
> > a method for measuring a capacitance Cx is available.
> > Here is one simple method.
> >
> > 2A) For a moment shorten the leads of the Cx capacitor
> > with a wire to make sure it is discharged. If Cx is a set of
> > several capacitors then make sure that all component are
> > discharged before proceeding. Without doing this you may
> > get a wrong result. (The most reliable way of preparing a
> > setup for a measurement is to shorten all components at
> > the same time and then to disconnect the shortening wires.
> > Shortening only the external leads may not be sufficient
> > for some setups.)
> >
> > 2B) You must have a reference capacitor whose C is
> > known. Connect it to a dc source of known voltage, such
> > as U1=12 V, to fully charge it. Then disconnect it from
> > the source.
> >
> > 3) Connect the terminals of your fully charged C to the
> > terminals of the Cx box and measure the new voltage, U2.
> > The voltmeter must have very high impedance, so high
> > that U2 remains practically constant for at least 5 seconds.
> > Pasco electrostatic voltmeters are ideal for the purpose.
> >
> > 4) Convince yourself that the conservation of Qleads to
> > Cx=C*(U1-U2)/U2. Use this formula to calculate Cx.
> > Be aware that C should be of the same order of magnitude
> > as Cx. It is a good idea to have several reverence
> > capacitors. Use a larger C when U2 is too small, use a
> > smaller C when (U1-U2) is too small.
> >
> > 5) Do not wait too long before measuring U2, even with
> > a nearly ideal voltmeter, when Cx consists of capacitors
> > connected in series. Why is this important? Because the
> > implied assumption of "no effect from the leakage of
> > charge" may no longer be valid. This topic was discussed
> > here in 1994 (?) In most cases several seconds is not too
> > long but several hours is too long. Several minutes may
> > be too long for some electrolytic capacitors.
> > Ludwik Kowalski
> >
>
> --
> "But as much as I love and respect you, I will beat you and I will kill
> you, because that is what I must do. Tonight it is only you and me, fish.
> It is your strength against my intelligence. It is a veritable potpourri
> of metaphor, every nuance of which is fraught with meaning."
> Greg Nagan from "The Old Man and the Sea" in
> <The 5-MINUTE ILIAD and Other Classics>