Floating Magnets

Background Information for Teachers

Your students may already be familiar with magnets. You may have some magnets in your classroom, used to hold up artwork or other papers against a metallic surface. However, they may not know that magnets have two opposite poles, which we refer to as north and south. Similar or "like" poles will repel each other (push each other away). Opposite or "unlike" poles will attract each other (pull towards each other) as shown in Figure 1.

Image Credit: Ben Finio, Science Buddies / Science Buddies
Figure 1. Diagram showing how magnets can attract and repel each other depending on the orientation of their poles. The north and south poles are labeled "N" and "S" respectively.

Magnets can push and pull on each other even when they are not touching. You can notice this simply by placing two bar magnets flat on a table in a straight line with each other, and slowly sliding one towards the other. Depending on which way the poles are facing, when the magnets get close together, they will either slide apart or snap together (and if the magnets are not perfectly lined up, they might spin instead of moving straight). You can use this fact to make multiple magnets "float" in mid-air by setting them up so like poles always face each other, as shown in Figure 2.

Image Credit: Ben Finio, Science Buddies / Science Buddies
Figure 2. Floating magnets, set up with their poles facing in alternating directions so they repel each other.

Note: Your students may already be familiar with refrigerator magnets, which will stick to some metallic surfaces (filing cabinets, refrigerators, some whiteboards, etc.). However, some refrigerator magnets (the flexible kind) do not behave like the magnets you will use in this project. They have a series of very tiny alternating magnetic poles, instead of one big north pole and one big south pole. This type of magnet will not work for this project.

Additional Background Links

• Electricity, Magnetism, & Electromagnetism Tutorial, Science Buddies

Prep Work (2 minutes)

Engage (5 minutes)

1. Place your two large bar magnets face down on the floor (so students cannot see the N and S labels on the poles). For now, just refer to them as "metal bars" with your students.
2. Ask for a volunteer to take one of the metal bars, and (while keeping it flat and face down on the floor), slowly slide one of its ends towards one end of the other metal bar.

   What happened? What did you observe?

   The other metal bar moved when we brought the first metal bar close to it (the direction of the movement will depend on the orientation of the poles, which the students cannot see yet). You can introduce your students to appropriate scientific vocabulary: when the metal bars pull together, we say they attract. When they push apart, we say they repel.

3. Place the metal bars back in their original position and flip the first metal bar around. Ask another student to try the same thing.

   What happened this time?

   The second metal bar should have moved in the opposite direction this time.

4. Give the students a chance to ask questions about what just happened. For example, they might ask if there is something special about the metal bars, or why they seem to attract sometimes but repel at other times.
5. Flip the bars over and explain that they are magnets. Magnets have two ends, or poles, called north and south. The poles are labeled with N and S. Magnets can attract and repel each other even without touching. Now they will do an experiment to find out how the different poles attract and repel each other.

Explore (20 minutes)

1. Pair up the students and give them a few minutes for open-ended exploration with their magnets. Ask about their observations.

   What happens if you hold one magnet in each hand and bring them close together? What happens if you flip one magnet around and try again? What happens if you put one magnet down on your desk and slide the other magnet towards it?

2. Give each pair of students a copy of the student worksheet. Explain that they will now do an experiment to find out how magnet poles attract and repel each other.
3. Put one magnet down on your desk. Then test what happens when you slowly bring the other magnet close to it. As shown on the worksheet, try this with the poles facing different directions. Again, introduce vocabulary if needed: we call two poles that are the same (both north or both south) like poles. Two poles that are different (one north and one south) are called unlike poles.

   What causes the magnets to pull towards each other? What causes then to push away? Do you see a pattern in your results? Fill in the results on your worksheets.

4. Now look at your ring magnets.

   What do you notice about these magnets when you compare them to your bar magnets? What does this mean?

   These magnets do not have an N and S printed on them like the bar magnets do. We cannot tell where the north and south poles are just by looking at them.

   Using the information we just learned about magnet poles, can we come up with a test to figure out the north and south poles of the ring magnets?

   We can bring a bar magnet with labeled poles close to the ring magnet. The side of the ring magnet that is attracted to the bar magnet's north pole (or repelled from its south pole) is the ring magnet's south pole, and vice versa.

5. Test each one of your ring magnets, and use a marker to label the poles (the flat sides) N and S. Be careful to let the marker dry so you do not smudge it off with your fingers. Note: Your students should discover that the ring magnet's poles are on the flat sides, not the rounded side.
6. Place your marker upright in a ball of modeling clay so it stands straight up on your desk.
7. Place a single ring magnet over the marker so it slides down to the bottom.
8. Now, using what you have learned so far, figure out how you need to place a second magnet onto the marker so it will push away from the first magnet and float in mid-air. If your magnets stick together, pull them apart. Try to figure out what you did wrong, then try again.
9. Now, can you add a third magnet to the marker so it floats above the second magnet? Keep adding more magnets—can you get all six to float without touching each other?
10. See the Variations section for other things students can do if some of them finish early.

Reflect (5 minutes)

Discuss your results as a class. Could every group get all six of their magnets to float? If any groups could not get it to work, ask other students to help them troubleshoot. Can they find out what was wrong?

Ask the students to summarize what you learned about magnets:

• Magnets have two poles, north and south.
• Like poles (north-north or south-south) repel.
• Unlike poles (north-south) attract.

Assess

You can assess student understanding of this activity with the following tasks:

• Place a labeled bar magnet on a desk facing the student. Ask them to use another labeled bar magnet to either push the first magnet away, or pull it towards them, and explain what they are doing.
• Give the student one labeled bar magnet and one unlabeled magnet. Ask them to identify the north and south poles of the unlabeled magnet.
• Show the student a diagram of some combination of floating and connected magnets, like Figure 3. Ask them to build what they see in the diagram using a marker and their ring magnets. Observe how the students figure out how to put the rings on, and ask to explain why they do it this way.

Image Credit
Figure 3. Example setup where some magnets are attracted to each other and some are repelled. The poles are labeled for your reference—do not label the poles in the version you show the students.

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Physicist

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Career Profile

Physicists study how magnets push and pull on each other. They use very powerful magnets (much stronger than the ones you used in this lesson!) to smash tiny particles together and help us learn more about the universe. Read more

Mechanical Engineer

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Career Profile

Many of your toys probably have motors inside. Did you know that motors have magnets in them? Engineers design machines with motors and other moving parts. Read more

Lesson Plan Variations

• Have your students investigate how the strength of a magnet varies with distance. Try pressing down on the top ring magnet once all the magnets are floating on the marker. Does it get harder or easier to push as the magnets get closer together? When you slide two bar magnets together, how close do they need to get before they push/pull on each other?
• Investigate which materials in your classroom are magnetic. What materials will the magnets stick to? What objects can you pick up with the magnets? What do these materials have in common?
• If you have different types of magnets available in your classroom, let your students compare how strong they are. For example, from how far away can they pull another magnet towards them? How many paper clips can they pick up?