Wayne Sallee wrote:
The difference is that a submersible pump like a powerhead works by
giving an alternating magnetic charge. You will notice that when a
powerhead starts up, it's a 50/50 chance as to which way it will spin,
and if something gets stuck in there, like if you stick your finger on
the impeller, you will notice that the impeller vibrates back and forth.

Called a "stepper" motor.

But a external pump like little giant, uses windings that are charged in
order one after another, depending on the position that the shaft is in,
because the electrical contacts on the shaft control the polarity of the
electrical field being generated.

Called a "squirrel cage" motor.

See http://en.wikipedia.org/wiki/Electri...ents_and_types

George Patterson
If there are obstacles, the shortest path between two points may be the
crooked one.