Eisco Labs 13 eddy current demonstration. This demonstrates the amazing Lenzs law. Consists two masses drop down a 33cm copper tube. One is steel, one is a neodymium magnet. Two masses drop down a 33cm copper tube. One is steel, one is a neodymium magnet. When students see the magnetic mass falls more slowly than the steel mass, you can introduce them to electrical eddy currents. These currents oppose downward motion through a moving magnetic field created by the falling neodymium magnet.