On Fri, 14 Nov 2003, Daniel L. Katz wrote:

> the resistance of the spark gap itself depends on the current
> flowing, temperature, pressure, and other factors. ohms law doesn't apply
> to gaseous conduction.

Sure it does, just on an instantaneous basis.  Ohms law is correct for
*whatever the spark gap's resistance is at that moment*, but that
resistance varies from moment to moment.  If you measure the current and
voltage you can derive what the resistance of the gap is under those
conditions.

> what about the resistance of a copper wire carrying a spark current? even
> ignoring reactive effects, since the current is pulsed, the the effective
> cross sectional area of the wire is reduced by the skin effect in a
> complicated time varying manner.

Again, Ohm's law still works, it's just that the effective resistance of
the wire changes with frequency.

> diodes are useful because they don't obey ohms law.

It's not so much that they don't obey ohms law as that they're not pure
resistance devices.  You can plot a resistance curve for a diode but it
varies with voltage and polarity.  As you say, that's what makes it
useful.

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