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Lesson 3 Summary
Use with pp. 54–59
Lesson 3: How are electric currents and
magnetic fields related?
Vocabulary
electromagnet a coil of wire through which electric current passes,
creating a magnetic field
In 1820, a scientist named Hans
Christian Oersted ran electric current
through a wire. There was a compass near
the wire. When Oersted turned on the
current, the compass needle moved. The
electric charges created a magnetic field.
Moving Magnets Produce
Electricity
In 1831, the scientist Michael Faraday
put a moving magnet inside a wire coil.
This created an electric current.
Faraday invented a device called a
dynamo. A dynamo has a magnet inside
a coil of wire. When the magnet moves
back and forth, the dynamo produces
electricity. When the magnet stops moving,
the electric current stops. This shows that
electric current and magnetic fields are
related. Electric charges in motion create
magnetism. Electric charges in motion also
create electric current. Electromagnets
An electromagnet is made of a coil of
wire. Electric current moves through this
coil of wire. The moving electric current
creates a magnetic field.
Here are some ways to make an
electromagnet stronger. You can put
an iron or steel bar inside the coil of
wire. A thicker bar makes a stronger
electromagnet.
Or, you can add more coils or more
12 Chapter 2, Lesson 3 Summary
layers of wire. You can also wrap the coils
more tightly around the bar. A stronger
current also makes an electromagnet
stronger.
Applications of Electromagnets
People use electromagnets in many
ways. Computers use electromagnets.
A computer’s hard drive is covered with
magnetic material. When you save a
file, the computer uses electromagnetic
fields. The electromagnets “write” the
information.
Doctors use electromagnets to see
tissues deep inside the body. MRI stands
for Magnetic Resonance Imaging. An
MRI machine produces a magnetic field.
This field affects particles in the body. A
computer uses these particles to take a
picture of the body.
Some flashlights use an electromagnet to
make light. When you shake the flashlight,
a magnet moves through a coil of wire.
This produces the electric current. The
electric current produces light.
In junkyards, large cranes have strong
electromagnets in them. The cranes use the
magnets to lift large, heavy pieces of metal.
Intervention Study Guide
© Pearson Education, Inc. 4
Electric Current Produces a
Magnetic Field
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Lesson 3 Questions
Use with pp. 54–59
Lesson 3 Questions
1. How does a dynamo produce electricity?
2. What are two ways to make an electromagnet stronger?
© Pearson Education, Inc. 4
3. What is one device that people use every day in school and at work
that uses electromagnets?
Intervention Study Guide
Chapter 2, Lesson 3 Questions 13