On Fri, 14 Nov 2003, David Beierl wrote:

> I'm guessing that it remains a good bit higher since we're dealing with a
> spark (vs an arc which can carry heavy current at low voltages by
> transferring metal ions across the gap).

Actually, mainly it's the air that's ionizing.

Extinguishing the arc is a major design consideration for really large
circuit breakers, like the ones in power transmission line systems.  One
of the more compact methods is to put the contacts inside a sealed chamber
which is evacuated to a high vaccuum.  No air means nothing to ionize
to carry the arc current.

David Brodbeck, N8SRE
'82 Diesel Westfalia
'94 Honda Civic Si -- For Sale
'86 Volvo 240DL wagon