Download Section 22.3 - CPO Science

ELECTRICITY AND MAGNETISM 22.3
Chapter Twenty-Two: Electricity
and Magnetism
22.1 Properties of Magnets
22.2 Electromagnets
22.3 Electric Motors
Chapter 22.3 Learning Goals
Describe the role of electromagnetism
in the function of electric motors and
generators.
Contrast energy transformations in
electric motors and generators.
Explain the principle of
electromagnetic induction.
22.3 Electric motors and
generators
Permanent magnets and
electromagnets work together to make
electric motors and generators.
The secret is in the ability of an
electromagnet to reverse its north and
south poles.
22.3 Electric motors
Around the edge
of a disk are
several magnets,
their alternating
north and south
poles facing out.
22.3 Electric motors
To make the disk
spin, you bring a
permanent magnet
close to its edge.
The free magnet
attracts one of the
magnets in the disk
and repels the next
one.
The disk is a “rotor”
because it rotates.
22.3 Electric motors
In a working electric
motor, an
electromagnet
replaces the magnet
you reversed with
your fingers.
The electromagnet
switches its poles to
make the rotor keep
turning.
22.3 Electric motors
As the rotor spins,
a commutator
reverses the
direction of the
current in the
electromagnet.
22.3 Electric motors
Motors have three
parts:
1. A rotor with magnets
that alternate.
2. One or more fixed
magnets around the
rotor.
3. A commutator that
switches the direction
of current to keep the
rotor spinning.
22.3 Battery run electric motors
 An electric motor that runs from
batteries has the same three parts.
 The permanent magnets are on the
outside, and the electromagnets turn
in the rotor.
22.3 Battery run electric motors
 A simple battery
powered motor
has three
electromagnets.
22.3 Electromagnetic induction
 Motors transform electrical energy into
mechanical energy.
 Electric generators do the opposite.
 They transform mechanical energy into
electrical energy.
 The process of using a moving magnet to
create electric current is called
electromagnetic induction.
22.3 Electromagnetic induction
 A moving magnet produces a current
in a coil of wire.
22.3 Generating electricity
 A generator converts mechanical
energy into electrical energy using
the law of induction.
 As long as the disk is spinning, there is a
changing magnetic field through the coil
and electric current is created.
Investigation 22C
Electromagnetic Forces
Key Question:
How does an electric motor work?
Under the Sea
Have you ever wondered
what it would be like to take
a “walk” on the seafloor?
Engineer Jim Varnum gets to
go “down under” regularly,
because he is a pilot of an
extremely complex robot
called Jason II. This robot
dives deep into the ocean
and is used to take pictures
and collect data from the
seafloor.