Activity 8: Magnetic Fields

MAGNETIC GLOBE

Summary:

Have you ever seen Earth's magnetic field? Students will model the Earth's magnetic field using a ball, a neodymium magnet and staples.

Instructional Method:

Experiment

Goal:

To illustrate the presence of magnetic fields.

Objectives:

Students will be able to:

• Model the Earth's magnetic field
• Explain in their own words why north is in the north and south is in the south

Time:

Activity: 30 min.

Materials Needed:

• baseball size or smaller foam ball
• neodymium magnets
• utility knife
• glue
• staples and a stapler
• compass

Vocabulary:

force field
magnetic field

Background:

Remember, the Earth has a north pole and a south pole, just like our bar magnets. So the Earth's magnetic field should look similar to the one we just illustrated in the last activity, only we now have a way to make that model three-dimensional. Using a small foam ball and a neodymium magnet, you can place used (bent) staples gently on the surface of the ball and see the Earth's magnetic field. Try holding a compass on the surface of the ball and see what happens.

Instructional Procedures:

1. If you are making your own magnetic globe, start by cutting a slit into the side of your foam ball. Only cut about half way through, our goal is not to make two pieces of the ball, but to make a hole big enough to slide magnets in. Only neodymium magnets are strong enough for this activity and depending on the size of your ball, you may need to use more than one magnet inside the ball. Experiment until you find the right combination. When you can attract a staple to the side of the ball, you have the right strength. Close the opening in the ball with glue, sealing the magnets inside of the ball. For fun, you can draw the continents on the ball, just remember which direction the magnets were facing: the north pole of the magnets should correspond with the north pole of the globe.
2. Expend approximately 30 used staples, (squeeze your stapler with no paper in it, and collect 30 bent staples).
3. Practice placing the staples onto the globe; at the equator they should lie flat. At the two poles, the staples should stand up vertically. In between the equator and the poles, the staples will stand out at varying angles representing the lines of magnetic force around the globe.
4. (click here to view a globe using staples to show magnetic field)
5. Either repeat this experiment in the classroom as a demonstration for a class, or have the students break into smaller groups and try it themselves. You would need one globe per group of students.
6. Have the students draw what they are observing and explain, in their own words, what is happening and why.

Discussion:

Which way are the staples pointing at the two poles of this model of the Earth? Why? What about at the equator, why are the staples laying flat there? What are the rest of the staples doing? Does it look like something we have already seen? Do you think that our planet Earth has the same lines of force around it as we see here? Think of a compass as one of our staples here, what way would it point on the equator. What about at the poles? Why can't we see it standing up at the poles? Why is the Earth's magnetic field important? What would happen if the poles switched, and our compasses started to point south instead of north? What would life be like if there was no magnetic field at all?

Extension:

Have the students hypothesize about how life would be different if the poles switched again, like they have in our geologic past. Have them write a creative story about a day in their life if the poles switched. Perhaps turn this into its own activity, using increased information on the poles switching. Have students try an orienteering course, only backwards.

Included National Parks and other sites:

Geology of North Cascades National Park
High Arctic Islands National Park (Canada)
Lassen Volcano National Park

Photos:

Earth
compass
lodestone
magnetite

Utah Science Core:

Kindergarten Standard 4 Objective 3
5th Grade Standard 3 Objective 1, 2

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