Re: Sparks - an experimental approach.

["Ludwik Kowalski" <KowalskiL@Mail.Montclair.edu>]

Dear Brian:

How can I disagree with something as fundamental as conducting
an experiment to validate a statement about nature? But the
experiment must match the question. (The methodology used by
philosophers and lawyers is also part of physics.) It is not worth
starting an experiment before clearly defining what has to be
tested, and before being sure that the experiment is properly
designed for the purpose.

You say that dry air is a better insulator than partial vacuum.

To me this is is the same as saying that the resistivity (Ohm*m)
of dry air is higher than that of partial vacuum. How do we
determine resistivity? We measure I for different V and we
identify  R as the constant slope of the curve. Then we calculate
resistivity from R, and from geometrical considerations. Doing
this for the parallel plates is the most simple way (conceptually)
of finding resistivities at different pressures. Call this a flat plate
ionization chamber method, if you wish. In practice the
experiment is not easy because the currents are very  small
(nA and less, depending on the geometry and on d.o.p.) .

I think we understand each other very well. The issue boils
down to "what is meant by a better insulator". To me it means
"higher resistivity ". That is why I think that the "sharp point"
configuration should not be used to verify your assertion.  You
seem to have a different operational definition of "better
insulator".  That's all. The issue of that kind can not be resolved
by an experiment. I am sorry for being tiresome.

                                                                    Regards,
Ludwik Kowalski
Brian Whatcott wrote:

> Ludwik, you are becoming tiresome. If you don't want to implement my
> experimental protocol, on the basis that Ohm's law would be invalidated by
> sharp point electrodes or some such argument, then by all means, YOU
> recommend an experimental protocol.  But you do yourself a disservice if you
> continue in a theoretical mode, which becomes the playground of philosophers
> ( and lawyers?), when a simple experiment would resolve the issue.