|MLA Citation:||Bloomfield, Louis A. "Question 807"|
How Everything Works 21 Jan 2018. 21 Jan 2018 <http://howeverythingworks.org/print1.php?QNum=807>.
To demonstration this effect, you can lower a very strong magnet above a rapidly spinning aluminum disk. In my class, I spin a sturdy aluminum disk with a motor and lower a 5 cm diameter disk magnet onto its surface. I hold the magnet firmly with a strap made of duct tape, so that the magnet won't fly across the room or flip over as it descends. Instead of touching the spinning disk, the magnet floats about 2 cm above it. If you try this experiment, don't spin the aluminum disk too fast or it will tear itself apart. It should spin about as fast as an electric fan on high speed. Also, be careful with the magnet, because it will experience magnetic drag forces as well as the magnetic lift force. If you don't hold tight, it will be yanked out of your hand.
For a simpler experiment that anyone can do, float an aluminum pie plate in a basin of water and circle one pole of a strong magnet just above its surface. The pie plate will begin to spin with the magnet. You are again inducing currents in the aluminum, making it magnetic. While the forces here are too weak to lift the magnet in your hand, they are enough to cause the pie plate to begin spinning, even though you never actually touch it. This technique is used in many electric motors. That's physics for you—the same principles just keep showing up in seemingly different machines.