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Grades 3-8


How important are magnetic fields to our everyday life? Very important! Without magnetic fields, there would be no electricity generated, sailors or pilots would not be able to orient themselves and there would be no batteries to power our automobiles.

In this lesson, students will investigate how a magnet works and how we use the Earth's magnetic field to orient ourselves. This lesson is part of an overall unit on magnetism and is a follow-up to an introduction to magnetism. In their introduction, students will have "discovered" what materials are magnetic and what materials are attracted to magnets by investigating magnets and their properties.

Here's a way to grab your students' attention and focus it on magnetism: Gather a zip-lock sandwich bag, a breakfast cereal that is advertised as being "Fortified With Iron," and a small magnet that is painted white. Place the magnet in a sandwich bag and fill the bag 1/3 of the way full with the cereal. Seal the bag and shake it vigorously for about one minute (you can try pulverizing the cereal first if you want to). When you have finished, inspect the magnet for iron filings attached to it. When they say a cereal is fortified with iron, they aren't kidding!
ITV Series
Electromagnetism, #1: Earth's Magnetic Field
Learning Objectives
Students will be able to:
For each group of four students:
For the teacher's use in the lesson:
Pre-Viewing Activities
Present the following question to the students: " Does a magnet have equal attraction, or grabbing power, everywhere on its surface; or, does one part of a magnet have a stronger attraction than another?" After polling the class for their hypotheses, post the results on the blackboard. Next, solicit suggestions for developing an experiment to see how we can find out the answer to our question.

Divide the class into groups of four students each and give each group a gallon-sized zip-lock food storage bag containing two lengths of string about one-foot long, masking tape, bar magnet, box of about 100 small paper clips, and a container slightly larger than the magnet.

Have the groups complete the following procedures: Tie one string to each end of the bar magnet. Tape the other end of each string to the edge of a desk or table (making the magnet level), leaving sufficient clearance from the floor to maneuver the container under it. Spread the paper clips in the container and raise the container under the magnet slowly until the magnet rests on the clips. Slowly remove the container from under the magnet. Observe where the clips cling to the magnet. Record observations, and include a short written description as well as a drawing.

When each group has completed their activity , have a representative from each group present their results to the class and discuss them. Discussion should include the observation that more clips attached themselves to the ends of the magnet than anywhere else.

Select one of the student drawings to temporarily post on the lefthand side of a large piece of white poster board taped to the blackboard.

At this point, ask the class if they can think of a way of making the invisible lines of force plain to see. Ask questions like "How many of you have ever seen a magnetic toy that you can draw with?" This should help cue them to thinking about little pieces of something that the magnet can move. Explain that those little bits of something are metal filings. We get filings by running a piece of metal over a file. The little bits that get scraped off are filings. These filings are made from iron, one of three special metals that can be magnets, or can be attracted to magnets. (The other two metals are nickel and cobalt.) Hold up your container of iron filings and explain we can make some of the invisible lines of force easy to see by sprinkling some filings on a piece of paper laid flat over a magnet.

Instruct each group to lay their bar magnet on a level surface, such as a desk or table top, and cover the magnet with a piece of paper that is stiff enough not to flop over the magnet, yet not too thick that the magnetic field is shielded by it. Visit each group and dispense some iron filings to be spread on the paper. Instruct the students to observe any patterns they see, sketch them and write a short description of what they see. Meanwhile, turn on the overhead and project the image on the piece of white poster board next to the student drawing of the paper clip exercise. Place a bar magnet on the surface of the projector and cover it with a blank sheet of overhead transparency. Sprinkle some filings on it and distribute them evenly. This should duplicate the results the students are observing and will provide a comparison to the student drawing of the paper clips. Most of the filings should be clustered about the poles of the magnet, making it visible why the paper clips were also attracted to these areas. Discuss the magnetic lines of force and magnetic fields with your students.

As a follow-up activity, have the students explore the strength of the poles of differently shaped magnets to determine if the shape of a magnet affects its areas of strength. To accomplish this, do the following:

Have each group tape one bar, donut and "U" shaped magnet to a desk or table top so that each magnet hangs over the edge.

Space them far enough apart so one doesn't affect another.

Bend open the end of a paper clip so that it forms a hook and attach one to each magnet at one pole. (The poles for the bar and "U" shaped magnets are at their ends. The poles for the donut magnet are the flat circular surfaces.) Do not hook it over the magnet.

To each magnet, attach one paper clip at a time to the hook and count how many clips each hook can hold. Try several runs through this exercise and graph the average.

Keep records of the results and graph them. (Review the four parts of a graph: the title, a label for each axis, and the data. A bar graph is best suited for this exercise.)
Focus Viewing
To give students a specific responsibility while viewing, ask students to be on the lookout for the following information throughout the course of this video: modern day uses of magnets and magnetic fields the history of magnets the construction and use of a compass the shape of magnetic fields around a bar magnet and the Earth the definitions of magnetic poles and magnetic declination the difference between geographic and magnetic poles

You might want to post these items on an overhead projector or poster. The following page is a template from which you can make an overhead transparency. You can also make copies for the students to have at their desks to jot down some notes as they go along.

Going My Way? Focus For Viewing


Be on the lookout for the following information which will be discussed after viewing the video:

Modern day uses of magnets and magnetic fields.

The history of magnets.

The construction and use of a compass.

The shape of magnetic fields around a bar magnet and the Earth.

The definitions of magnetic poles and magnetic declination.

The difference between geographic and magnetic poles.

Viewing Activities
Show opening sequence from "Aliens would shut down a city if they could neutralize all magnetic fields."

PAUSE video when narrator says, "For the moment, however, this is only science fiction."

Ask: -"What does neutralize mean?"(to destroy or counteract a force - in this case magnetic fields)

Ask: "What would neutralizing magnetic fields have to do with cars and office buildings?" Have students hypothesize (part of their scientific method vocabulary) and give possible answers. (Magnetic fields are used to generate electricity and battery power.)

Re-alert students to look out for what civilization discovered magnetism. Why is a lodestone (magnet) called a magnet? How were early compasses made? RESUME video.

PAUSE: "These mysterious pieces of stone advanced sea exploration as never before."

Ask: "How did these stones advance sea exploration?" (They helped sailors find their way over great distances. By knowing which way was north, all other directions can be found.)

Ask above questions that students were alerted to and discuss student answers. RESUME video.

PAUSE: at spherical lodestone graphic where the narrator says, "So a compass placed anywhere on the lodestone sphere will align itself with the magnetic field."

Review the three diagrams posted on the blackboard.

Alert students to listen for the difference between the geographic and magnetic poles.

FAST FORWARD to the graphic of Earth in space after the heating of the magnet is shown. CONTINUE video where the narrator says, "But these magnetic poles do not coincide with the geographic poles of the Earth."

PAUSE: at graphic of the Earth in space with both sets of poles displayed.

Ask: "What are the geographic poles?" (The points on the Earth where the imaginary axis runs through. Review that the Earth spins on its axis once every 24 hours giving us our night and day.) Ask: "What are the magnetic poles?" (Review earlier information that the magnetic poles mark where the lines of force are closer together at opposite ends of a magnet or the Earth.)

Ask: "Will a compass point to the geographic north pole?" (No. From most places on the Earth, it will not.)

RESUME video.

STOP video after the graphic of the magnetic north pole marker zig-zagging around the globe.

Review the items the students were alerted to prior to watching the video. Use the worksheet provided earlier as a guide.
Post-Viewing Activities
For the post-viewing activity, each group of students will construct their own simple compasses. Use the following page, labeled "Going My Way? - Activity #1," as a handout for the students. You can also use it as an overhead to help walk the class through the entire set of instructions before actually trying them.

Once the compasses are constructed and have been verified by the "real" compasses, have the students construct a map of the classroom and/or schoolyard. Using their hand-made compasses, the students need to identify the directions in which several objects lie about the classroom/school yard, use symbols to identify them and orient the maps accordingly. Have the students follow the directions on the sheet labeled "Going My Way? - Activity #2" to help them in this exercise.
Action Plan
Invite sportsmen and women (hunters and hikers especially), as well as airplane pilots or sailors (professional and amateur) to the classroom to discuss and/or demonstrate the importance of a compass to their sport or livelihood.

Visit your local airport or marina to discuss the importance of a compass to navigation.

Contact your local Boy Scouts of America supplier and request a set of orienteering games and play them in your schoolyard (space permitting).

Make your own compass rose on your school grounds. At noontime, the Sun is due South from you. This means any shadows it casts are falling in the due North direction. Once you have North marked, South is directly behind you, East is to your right and West is to your left. Try placing the intercardinal directions of Northeast, Northwest, Southeast and Southwest too!
Mathematics: design a compass course to be completed on school grounds specifying distance and direction.

Art: draw a map of the school grounds and include a key explaining the scale, symbols and directions.

Physical Education: perform the above compass course.

Social Studies: tie into unit on map and globe skills.

Science: tie into a unit on the Earth's atmosphere, especially regarding the northern and southern lights and their relationship to the Earth's magnetic poles (just as the magnetic lines of force are closest together at a magnet's poles, so too are they at the Earth's poles. When electrical particles from the Sun reach the Earth, they gather at the poles producing glowing lights in the sky).

Language Arts: Read The Hatchet by Gary Paulson. It's a story about a boy who crashes in an airplane and uses all his resources to help him survive.

Master Teacher: Daniel Reidy

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