These aluminum paddles have no magnetic properties by themselves. However, as they are swung through a magnetic field, they clearly experience a strong damping force, indicating that they are indeed affected by it. The paddles gain electromagnetic properties as they move through a magnetic field, as the movement through an electric field induces currents within the material that act opposite the magnetic field of the magnet. These currents, which are the culprit behind the damped motion, are known as "eddy currents."
Uses the variable gap magnet.