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What is an Electric Motor?

An electric motor is a device that
transfers electrical energy into rotational energy.
Something that spins round has rotational energy.
Rotational energy is a form of kinetic energy.

Electric motors have a wide variety of uses.

How does a Simple Electric Motor Work?

The catapult effect (motor effect) is used to
make a simple electric motor spin round.
The wire is pushed in the opposite direction
if the direction of the current through it is reversed.

In a motor, the wire is wound around a central block
called an armature.
A spindle through the armature allows it to rotate.
The current flows in opposite directions on each side
of the armature, so one side is pushed while
the other is pulled. This makes the armature rotate.

Forces on a Spinning Motor

After the armature has rotated through half a turn (180°),
then the side of the armature being pushed upwards
in the above picture is now on the left
and the side being pulled down on the right. The
armature would be trying to turn in the opposite direction.

For the armature to continue to spin in the same direction,
the direction of the current flowing through the wire
must be reversed every half turn. This is achieved
using a split - ring commutator (see the next page).

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