On Mon, 2006-05-22 at 00:21 -0700, Marcel Birthelmer wrote:
> I'll try, but I'm very possibly wrong, please correct me.
> 
> 1) When the circuit is closed, think of the two contacts approaching
> each other slowly. At some point they will be close enough so that the
> voltage different is higher than the breakdown voltage of whatever is in
> between them, like air for example. This then causes the air to ionize
> which forms a conductor channel, and that's a spark - the brightness
> depends on, among other things, how much current is drawn through this
> channel, which is why heavier loads spark more.

I believe "some" of the spark also comes from the heating/vapourization
of the materials that are carrying the current. A good example would be
MIG welding.

TTYL

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