Download Unit 4 Lesson 5

Unit 4 Lesson 5 What Are Magnets?
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Unit 4 Lesson 5 What Are Magnets?
Florida Benchmarks
• SC.4.P.8.1 Measure and compare objects and
materials based on their physical properties
including: mass, shape, volume, color, hardness,
texture, odor, taste, attraction to magnets.
• SC.4.P.8.4 Investigate and describe that magnets
can attract magnetic materials and attract and
repel other magnets.
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Unit 4 Lesson 5 What Are Magnets?
Magnets Are Everywhere
• A magnet is an object that attracts iron and a few
other materials.
• Magnetism is a physical property.
• Many magnets are made of iron. They attract
objects that also are made of iron.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 5 What Are Magnets?
Magnets Are Everywhere
• Two factors that affect a magnet’s pull are barriers
and distance.
• A thick barrier weakens a magnet’s pull on an
object.
• The greater the distance between the magnet and
object, the weaker the pull.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Fields and Poles
• Each magnet has two ends, or poles.
• A magnetic pole is the part of the magnet where
the force is the strongest.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Fields and Poles
• One pole is “south-seeking,” and the other pole is
“north-seeking.”
• The south-seeking pole is an S pole. The northseeking pole is an N pole.
• Earth has an N pole and an S pole. As a result, the
whole planet is a magnet.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 5 What Are Magnets?
Magnetic Fields and Poles
• Like poles are poles that are the same. Like poles
repel, or push away, each other.
• Unlike poles are poles that are different. Unlike
poles attract each other.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 5 What Are Magnets?
Magnetic Fields and Poles
• A magnetic field is the space around a magnet in
which the force of the magnet acts.
• The magnetic field is strongest at the poles and
weakest in the center of a magnet.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Force
• A weak magnetic field forms around a wire when
electricity flows through a wire.
• If a wire carrying electricity is wrapped around an
iron object, such as a nail, an electromagnet
forms.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Force
• Wrapping more coils of wire around the nail
strengthens the magnetic field. The magnet will
be stronger.
• If the flow of electricity stops, the nail is no longer
magnetic.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Force
• Electromagnets are used in everyday objects.
They are used in telephones, televisions, and
motors.
• A motor is a device that uses electricity to make
things move.
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Unit 4 Lesson 5 What Are Magnets?
Magnetic Planet
• The whole planet Earth acts like a giant bar
magnet.
• It has poles that attract and repel. It also has a
magnetic field.
• A compass points toward the north pole.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 5 What Are Magnets?
Magnetic Force
• Earth’s magnetic poles and geographic poles
aren’t in the same place. They are about 700 km
apart.
• Iron in Earth’s core creates the magnetic field. The
field looks much like that of a bar magnet.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 5 What Are Magnets?
Magnetic Force
• Magnets are used in computers, trains, MRIs, and
junkyards.
Copyright © Houghton Mifflin Harcourt Publishing Company