Electromagnets
Lesson 6
How are electromagnets used?
What Is An Electromagnet?
 A magnet that has coils of
current-carrying wire
around an iron core
Objective
Students know the role of electromagnets in the
construction of electric motors, electric
generators, and simple devices, such as door
bells and earphones
How are magnets used in our own
backyard to produce electricity?
Answer: at a wind farm!
The wind spins turbines that use
magnets and wires to produce
electricity.
How do wind turbines make
electricity?
A wind turbine works the opposite of a fan. Instead of using electricity
to make wind, like a fan, wind turbines use wind to make electricity.
The wind turns the blades, which spin a shaft, which connects to a
generator and makes electricity.
Why do you think that places like
these are called “farms”?
Where in California would you
expect to find places like this?
Name forms of energy?
sound
light
thermal
energy
chemical
energy
electricity
energy
heat
Where does that word come from?
Energy conversion- from the Latin word
convertere which means “to turn”. Energy
conversion means to turn one form of
energy into another. Example- light or heat
into electricity or sound.
Kinetic- comes from the German worked
kinein, which means “to move”. Kinetic
energy is energy of motion.
Doorbells and Speakers
A doorbell has an electromagnet with a freely moving rod. Pushing
and releasing a button turns the current on and off. When the current
is on, the rod moves into the coil. When the current is off, a spring
pushes the rod out of the coil. A metal chime at each end of the rod
makes the Ding! Dong!
Speakers and earphones also have electromagnets. When you sing
into a microphone, you send sound energy through the air. It then
changes the sound energy into electrical energy that flows through
wires as a current. The electrical energy is converted back into sound
when it reaches the speaker.
Electric Motors
An electric motor is a device that changes electrical energy into kinetic
energy. Motors usually cause rotation, or a spinning motion.
For a motor to keep turning, the current must keep changing direction.
The coil becomes an electromagnet when it receives a current. The
poles of the electromagnet are attracted to the opposite poles of the
permanent magnet so the coils turns.
As the direction of the current changes, the coil and permanent
magnet keep attracting and repelling each other.
Generators
A motor converts electrical energy into kinetic and other forms of
energy.
A generator is a machine that converts other forms of energy into
electrical energy.
Any kind of energy that can move a coil of wire inside a magnetic field
can run a generator.
In an emergency, people use a generator to provide electricity for the
lights or a stove. Energy plants use huge generators that have
electromagnets.
What does an electric motor do?
A
makes things stop running
B
changes kinetic energy to kinetic energy
C
changes electric energy to kinetic energy
What does a generator do?
A
It turns other forms of energy into electricity
B
It converts electrical energy into kinetic
C
It makes doorbells and speakers work
A student has a portable light that does not
use a battery. She has to turn a handle very
fast to make the light come on. What is inside
the device?
A
a fuel
B
a motor
C
a generator
D
a wind turbine
Which of the following does not
work by using an electromagnet?
A
blender
B
electric racing toy
C
compass
D
CD player
Can a speaker work without an
electromagnet? Why or why not?
A
No, because the changing current in the
electromagnet is what makes the speaker vibrate
and produce sound waves.
B
Yes, the speaker can work without an
electromagnet because the music makes the cone
move
Let’s explore electromagnets and
motors on hspscience…
http://www.harcourtschool.com/menus/sci
ence/grade4_ca.html
The End