Want to see a really neat way to get magnetic fields to interact with each other? While levitating objects is hard, bouncing them in invisible magnetic fields is easy. In this video, you’ll see how you can take two, three, or even four magnets and have them perform for you.
Are you ready?
Materials:
- 3 identical magnets
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Download Student Worksheet & Exercises
Did you notice that if the north pole of the bottom magnet is up, then the south pole of the magnet stacked above it will be down? The stack holds together because opposites attract (north-south). You probably already knew that, right? But notice when you pull the top magnet to the side the bottom south face is repelled into the air above the north face of the fixed magnet. So what gives?
Remember that a magnet isn’t strictly north or south. There are field lines that connect the two poles. The field lines start at one end and swoop down to the other and back again like in this picture to the left, reversing from north to south as it does so. This is why the south face is repelled – because it’s actually the magnetic fields that are doing the repelling.
You can adjust your two bouncing magnets to have nearly the same ‘bouncy’ (frequency) by changing their distance apart. Notice that when one magnet starts bouncing, the magnetic field changes, which pushes and pulls on the other magnet. The two magnets interact with each other through their magnetic fields, pushing and pulling each other into resonance.
Once you’ve mastered two magnets, why not try three? Or four? What happens when you bring a conductor, like a thick sheet of copper, aluminum (cookie sheet or cake pan) nearby? The eddy currents created in the metal by the moving magnet created an opposing magnetic field that work to ‘brake’ the moving magnet and stop it from bouncing.
While this activity may seem a bit trivial (and a little fun), the idea of a magnetic field is one of the greatest leaps ever made in science. Scientist Michael Faraday imagined the idea that a magnet had not only a magnetic field, but that it cold push and pull on other magnets and moving electric charges. This crazy idea was so wild that it took many scientists a lifetime to come to terms with it… as it replaced an older idea from Newton that had stood for centuries.
And, as usually happens when someone has a new bright idea, others are quick to add to it. Shortly after Faraday’s idea about magnetic fields and electrical charges, Maxwell combined complicated mathematics (stuff you’ll only see at a university) into his four famous equations (Maxwell’s Equations) that describe all electric and magnetic fields.
Exercises
- Why does the magnet float?
- After you tap the floating magnet, does it vibrate for a short or long time? Why?
- Why do we stack the magnets first before trying to levitate them?
- How many magnets can you get to interact while floating?
- When you float two magnets above the main magnet, how do the floating magnets interact with each other? Why do they do that?
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