Fremont Magnet Elementary

Earth's Magnetic Field

Standards:
b. Students know how to build a simple compass and use it to detect magnetic effects, including Earth's magnetic field.

f. Students know that magnets have two poles (north and south) and that like poles repel each other while unlike poles attract each other.

1. Where is a magnet strongest?

If you want to pick up a nail with a magnet, which part of the magnet will have the strongest pull?

Take a look at the picture of a magnet with iron filings around it. Look at the pattern it makes. Where do you see the most filings, at the ends or in the middle?

So where is the force the strongest?

The middle
The poles

2. Now Try This Challenge

Look at this picture. Where would the magnet be the strongest: number 1, 2, 3, or 4?

Drag your mouse across the red box to check your answer.

number 4

3. How do magnets work?

Inside a magnet the domains are all pointing in the same direction.

Inside metal that contains iron, the domains are pointing in opposite directions.

When a magnet is close to iron, the magnet's magnetic field pulls the domains in the iron so that they all face the same direction and that is why they pull together.

Watch this movie to see how this works.

4. How does a compass work?

The Earth is like a giant magnet. It has a north pole and a south pole. This giant magnet is what makes a compass work. No matter where you turn it, the needle of a compass will ALWAYS point to the north.

Click here for an explanation of the Earth's magnetic field.

Click here to watch a BrainPop movie about how a compass works.

Did you know that you can make a compass? To make a compass you need to turn a needle into a magnet. To turn the needle into a magnet, you need to make the domains inside the needle point in the same direction.

5. Review

Click on Revisewise Magnets to review how magnets work.

Back to 4th Grade Science