ELECTRICITY AND MAGNETISM 22.3 Chapter Twenty-Two: Electricity and Magnetism 22.1 Properties of Magnets 22.2 Electromagnets 22.3 Electric Motors.
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Transcript ELECTRICITY AND MAGNETISM 22.3 Chapter Twenty-Two: Electricity and Magnetism 22.1 Properties of Magnets 22.2 Electromagnets 22.3 Electric Motors.
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.