Demo 20-26 Eddy Current Tubes

A strong magnet falls with the acceleration of gravity inside a vertical glass tube. When the same magnet is allowed to fall inside a vertical aluminum tube it falls much more slowly. In a conducting tube the motion generates induced currents, which in turn produce magnetic fields that oppose the downward motion of the magnet. In this demonstration two cylinders, one of which is a strong magnet, are dropped through each of the tubes, as shown in Figure 1, encouraging the student to speculate on what is happening