Video analysis of eddy-current braking using ring magnets sliding along an aluminium pipe

Abstract A conventional magnet falling through a conducting tube becomes hidden, preventing direct observation of its complete motion. Here, ring magnets slide along the outside of a vertical aluminium pipe and remain visible for smartphone video tracking. Ferrite and neodymium ring magnets were investigated using Tracker software. The ferrite magnet continued to accelerate throughout the observed fall, whereas the neodymium magnet approached an approximately constant velocity of 0.52 m s −1 after a short transient. The contrasting position-time and velocity-time behaviours illustrate transient and terminal-motion regimes of eddy-current braking. The apparatus provides a simple classroom demonstration linking Lenz’s law with velocity-dependent drag and terminal motion.