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How is the direction of the Motor Effect
(or Catapult Effect) predicted by Fleming's Left Hand Rule?

If we show the two magnetic fields from the
wire and the permanent magnet (see the 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.
The wire is pushed at 90° to the direction of
the magnetic field from the permanent magnets.
This is called the motor effect (or catapult effect)
and is used to make a simple electric motor spin round..

Motor Effect - Catapault Effect

What is Fleming's Left Hand Rule?

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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