http://www.ck12.org Chapter 24. Magnetism
Lesson Summary
- Earth is a giant magnet with north and south magnetic poles and a magnetic field called the magnetosphere.
Evidence in rocks shows that Earth’s magnetic poles switched positions hundreds of times in the past. Scien-
tists think that Earth’s magnetic field is caused by the movement of charged particles through molten metals
in the outer core. - Earth’s magnetic field helps protect Earth’s surface and its organisms from harmful solar particles by pulling
most of the particles toward the magnetic poles. Earth’s magnetic field is also used for navigation by humans
and many other animals.
Lesson Review Questions
Recall
- What is the magnetosphere?
- Identify evidence for magnetic reversals in Earth’s past.
- List two benefits to organisms of Earth’s magnetic field.
Apply Concepts
- Use a bar magnet, a globe or large ball, and any other props you need to demonstrate to another student how
Earth is like a bar magnet.
Think Critically
- What is the relationship between Earth’s magnetic poles and Earth’s geographic poles?
- Explain why Earth is a magnet.
Points to Consider
In this chapter, you learned that Earth is a magnet because of moving charged particles in its outer core. In the
chapter "Electricity," you learned that moving charged particles create electric current. The next chapter explains
how electric current and magnetism are related.
- Based on what you now know about electricity and magnetism, can you predict how they are related?
- Do you think electric current could be used to create a magnet? How might this be done?