Magnets. How do they work? It’s not a miracle, even though magnets may seem like mysterious things. They push and pull certain materials—and can even make them levitate—without touching them at all, but they seem to leave other materials entirely alone. In this science fair project, you will conduct a simple magnetic levitation experiment and test a number of materials to see if they have any magnetic shielding effect on the magnet’s field.
- Powerful permanent magnet (large neodymium magnets are excellent, but should only be used with adult supervision!)
- String or thread
- Test materials (flat objects that can fit in a 1-inch gap. Glass, copper, wood, etc.)
- Testing platform (a stack of large books works well)
- Something to secure magnet (a stiff, wooden ruler wedged between the top two books is perfect)
- Build your testing apparatus. Stack some heavy books on a table so that you create a platform that’s at least a foot off of your work surface. There needs to be enough room for you to place test materials between the magnet and your work surface.
- Place a ruler on top of your stack of books so that about four inches sticks out over the edge. Place another heavy book on top of the ruler to secure it.
- Tape your magnet to the end of the ruler.
- Tie one end of the string to the paperclip.
- Move the paperclip closer and closer to the magnet until it starts to be attracted. Tape the other end of the string to the table when the paperclip is close enough to the magnet so that it will stay suspended in the air.
- Try pulling the string to the side. How far can you move it without making it fall? Is it hard to do? Why do you think so?
- Move the paperclip as close to the magnet as you can without it touching and re-tape it. Repeat step 4. Do you notice any differences? Is it harder or easer to pull the string to the side? Why?
- Take your test materials and place them, one at a time, in the space between the magnet and your paperclip. Think about what kind of effect they might have on the magnetic force before you do so. Do any of them change the attraction of the paperclip to the magnet?
When your paperclip is closer to the magnet, you can move the string farther than when the paperclip is farther away. None of the materials you used should have been able to block the magnet’s field. If you used iron or steel as a test material, the magnet should have attracted the paperclip even more strongly, but the effect may be too small to notice.
Your test of your materials has just gotten a null result, or, basically, nothing happening. Null results are important in science, because they can mean that you’re seeing something you don’t yet understand and should experiment on more. They also tell you more about the world: you now know that none of the materials you tested can block magnetic fields.
None of your test materials shielded, or blocked, the magnetic field because resistance to magnetism is usually a very small effect. Scientists have created special materials that can do so, but everyday objects aren’t able to do it very well. The only magnetic effect you might see with certain everyday objects is ferromagnetism. Ferromagnetism is the tendency of iron, nickel, and some other metals to become magnetic themselves when exposed to a magnetic field. This amplifies magnetic fields (which explains why putting an iron object between the magnet and the paper clip may have made the magnet more powerful), and can also be used to make electromagnets more powerful.
The reason the paperclip was so much more resistant to being pulled away when it was closer to the magnet is because magnetic forces follow what is called a power law. This means that they get weaker by the distance multiplied by itself twice. Depending on how your magnet is shaped, it will have either an r-squared or r-cubed power law relative to your paperclip. R-squared means you multiply the distance by itself and then divide the power of your magnet by that amount to get how strong the magnet is. R-cubed means multiplying the distance three times before you do the above.
Sound complicated? Here’s all you really need to know: magnets get weaker the farther away from them you go. It’s easy to see how powerful the magnet is up close, but when you’re just a few feet away, you feel nothing. That’s a power law in action. Try squaring or cubing a few numbers, starting with 1 and going up, to see just how big a difference distance can make.