What Makes an Electric Motor Work

1
What Makes an Electric Motor Work?

• The Science and Technology Behind Electric Motors

2
Introduction

• Were going to make a small working motor similar
  to the one pictured at the left but what makes
  this or any electric motor work? Lets check it
  out!

3
Electric Motors - The Magnets

• A magnetic field exists between the north and
  south poles of a permanent magnet.

4
Electric Motors - The Armature
Wire Coil
Iron Core
Shaft

• An electromagnet (wire coil) is wound on an iron
  core and the core is placed on a shaft so it can
  rotate. This assembly is called the armature.

5
Electric Motors - The Assembly

• The armature is placed in the permanent magnets
  magnetic field.

6
More Details

• The ends of the armature coil are connected to
  semicircular sections of metal called commutators
  (A B). Brushes (X Y) contact the rotating
  commutator sections and energize the armature
  coil from an external power source. (Important -
  the polarity of the armatures electromagnet
  depends on the direction of current flow through
  the coil.)

7

• A battery is connected to the brushes. Current
  flows into brush X to commutator section A,
  through the coil to section B, and back to the
  battery through brush Y, completing the circuit.
  The armature coil is magnetized as indicated in
  the sketch.

8

• The north pole of the armature is repelled by the
  north pole of the field magnet. The south pole of
  the armature is repelled by the south pole of the
  field magnet. The armature turns one quarter
  revolution, or 90 degrees.

9

• The north pole of the armature is attracted by
  the south pole of the field magnet. The south
  pole of the armature is attracted by the north
  pole of the field. The armature turns another
  quarter turn. It has now turned one-half
  revolution.

10

• As the commutator sections turn with the
  armature, section B contacts brush A and section
  A contacts brush B. The current now flows into
  section B and out section. A. The current has
  been reversed in the armature due to commutator
  switching action. This current reversal changes
  the polarity of the armature, so that unlike
  poles are next to each other.

11

• Like poles repel each other and the armature
  turns another quarter turn.

12

• Unlike poles attract each other and the armature
  turns the last quarter turn, completing one
  revolution. The commutator and brushes are now
  lined up in their original position which causes
  the current to reverse in the armature again. The
  armature continues to rotate by repulsion and
  attraction. The current is reversed at each
  one-half revolution by the commutator.