A quantitative magnetic braking experiment

Abstract

A popular demonstration which often accompanies the introduction of magnetic induction is that in which a strong button-shaped magnet is dropped through a long copper or aluminum tube. The induced currents cause a retarding force which dramatically slows the descent of the falling magnet. Here, we describe methods of calculating and measuring the terminal velocity and magnetic forces in the magnetic braking experiment. The techniques are quite accurate, inexpensive to perform, and are suitable for introductory courses in electricity and magnetism.