Re: Sparks - an experimental approach.

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

Why a sharp point instead of another flat plate? Aren't we referring
to conditions under which Ohm's law is applicable? In this region
resistivity does not depend on E, it is proportional to the density of
free charges. The fact that the mean free path is increasing when P
goes down has no effect, unless secondary ionization becomes a
significant factor.

Brain wrote:

> Take a low voltage filament lamp and break the glass bulb.
> Mount it in a bell-jar, mason-jar or some such with an adjacent anode;
> the three electrodes are led through the lid along with an airline.
>
>    For a modest pressure reduction provided by a salvaged compressor
> from a domestic fridge (or perhaps you have access to lab vacuum?)
> measure the anode current in the microamp range with the filament
> glowing faint-red, the anode held at say nine volts and the
> vacuum varied.
>
>  I fancy one will need to consider factors other than cosmic rays.
>
> Ah, but I hear you say, this is 'thermionic' emission.
>    Might you then replace the filament with a sharp point?