Unit 4 Lesson 5 What Are Magnets? Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 4 Lesson 5 What Are Magnets?

Copyright © Houghton Mifflin Harcourt Publishing Company


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.


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.


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.


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.




• One pole is “south-seeking,” and the other pole is “north-seeking.”

• The south-seeking pole is an S pole. The north-seeking pole is an N pole.

• Earth has an N pole and an S pole. As a result, the whole planet is a magnet.




• 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.




• 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.


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.


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.


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.


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.


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.


Magnetic Force


• Magnets are used in computers, trains, MRIs, and junkyards.

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Unit 4 Lesson 5 What Are Magnets? Copyright © Houghton Mifflin Harcourt Publishing Company