Electric Motor

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2

Slide 12

Armature

The armature is an electromagnet made by coiling thin wire around two or more poles of a metal core.

The armature has an axle, and the commutator is attached to the axle.

When you run electricity into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stator. So the armature spins through 180 degrees.

To keep it spinning, you have to change the poles of the electromagnet.

Slide 13

Commutator and Brushes

Commutator is simply a pair of plates attached to the axle. These plates provide the two connections for the coil of the electromagnet.

Commutator and brushes work together to let current flow to the electromagnet, and also to flip the direction that the electrons are flowing at just the right moment.

Slide 14

The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator.

Slide 15

Spinning Armature

Slide 16

Example of Motor

Slide 17

Answer the questions

Slide 18

A current-carrying coil in a magnetic field experiences a turning effect.

How can the turning effect be increased?

A increase the number of turns on the coil

B reduce the size of the current

C reverse the direction of the magnetic field

D use thinner wire for the coil

Slide 19

What are the directions of the force in the left and right loop?

Slide 20

A student sets up the apparatus shown in order to make a relay.

Which metal should be used to make the core?

A aluminium B copper

C iron D steel