"Jim Adney" wrote in message
...
Not so; you're forgetting the AC power line itself, which
obviously is carrying a fairly high current wheneve the
microwave is operating.

That's true, and I hadn't thought of that, but the amount of magnetic
field it would create really just depends on the amount of area inside
the current loop. Assuming that this is wired in the usual way, that
loop is pretty small, since the two conductors are parallel to each
other and maybe just 1/4" apart.

Yes, you'd think it was pretty small - but this happens all the
time. It just doesn't take that much field to affect the typical
CRT display. (I've seen AC fields all the way down to 0.1 Gauss
or a bit less still result in visible movement on the screen, during
mag. susceptibility testing - and just to put that in context, that's
something like a fifth of the strength of the Earth's field typical
in North America.) The problem is that it's an alternating
field; low-level DC fields simply cause a static displacement,
which you'll either ignore or adjust out with the centering controls,
but an AC field results in a very annoying jitter.

Bob M.