Re: Hardware Maint. on Time&Materials?

["Robert W. Kerns" <RWK%fuji.ila.dialnet.symbolics.com@RELAY.CS.NET>]

    Date: Wed, 24 Jan 90 15:26 PST
    From: Mabry Tyson <TYSON@warbucks.ai.sri.com>
    (Ok, I admit I once tried to tweak the center core of the horiz. size
    transformer with a hex wrench when I couldn't find my plastic adjustment
    tool.  In about 2 seconds in got too hot to handle.)

That's a good one.  This is getting away from Slug, but
I imaging some people may be a bit puzzled.

Magnetic hysteresis = energy loss, which is why the core in
the transformer is ferite, not metalic iron or steel.  I've
done this too, but with a stainless tool that is only very
weakly magnetic, so the heating wasn't very strong.  I never
thought of extrapolating it to an ordinary steel hex wrench.

(It's also hard to adjust when the presence of the adjusting
tool changes the circuit's behaviour far more than the
adjustment you are trying to make).

As long as I'm sending mail, I may as well relay another
fine physics tip:

Even at low voltages like doorbells, 12vDC equipment, etc.,
don't wire up inductive loads like buzzers, relays,
selenoids, or motors, with the power on with your bare hands.
You *WILL* get a nasty shock, with a *LOT* more voltage than
you THOUGHT you were working with.

It seems obvious to anyone familiar with inductors and
E=L*dI/dt, but it is astonishing how easy it is to forget
when you think you're comfortably working with low voltages
and low power.  "Uh... What happened?  Uh... Oh, yeah."