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The Catapult Effect and Fleming's Left Hand Rule.
If we show the two magnetic fields
from the wire and the permanent magnet (see previous page),
we can see that on one side of the wire
the fields have the same direction and repel the wire,
on the other side of the wire
the fields have opposite directions
and attract the wire.
This is called the catapult effect (or
motor effect).
You can predict which way the
wire will move
by using Fleming's Left Hand Rule.
The thumb, first finger
and second finger of the left hand
are all pointing at 90° to each other.
1. The thumb points in the direction of motion of the
wire.
2. The first
finger points in the direction
of the field
(from the permanent magnet)
3. The second finger points in
the direction of the current through the
wire.
This works
well in theory but in
practice it may be difficult
to get your thumb and fingers all pointing in the right direction.
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