Andy Dingley wrote:

You can't have "a copper bar" with "about 2V across it". The power
required to maintain such a voltage would be enormous.

If he shorts his welder, the voltage AT THE SHORT is zero. You are correct,
Andy. However, the connections and the welding lead have nonzero resistances,
and so some current is still flowing through those resistances and generating a
small voltage back at the welder. So he is also correct.

It's easy to think of a piece of welding lead as having zero resistance, because
in many ways that's an excellent approximation. However, *nothing* has zero
resistance except maybe a piece of superconductor.

His welder is a fancy one, too, one of those TIG stick machines.

GWE