"Tim Williams" wrote in message ...
"William J. Beaty" wrote in message
om...
I wonder where this 300V (or 1350V from Jim Lux' page) actually
comes from?

Nowhere. Tell me, how is stick welding performed?

Um... You don't know? And you just IGNORE the breakdown
equation without comment? OK, I'd like to hear your reasoning
for why that "Paschen rule" isn't important. We can send your
discovery to Jim Lux and he can add it to the High Voltage Handbook.




Stick welding has nothing to do with the electrostatic breakdown
of normal air which the OP was asking about. To start a welding
arc you have to TOUCH the stick to the workpiece. Once the arc has
formed the physics (and the voltages involved) are entirely different,
and you can pull the electrodes apart to a fairly large distance.
The physics is then that of e-fields within conductive plasma
which keep the plasma "alight." Seen a "jacob's ladder?" The
spark can only leap across an inch or so, yet once it has appeared
it can grow to many inches in length. The original question was
about that spark-leaping phenomenon, not about the length such a
spark can grow after it has started.