Arduino-Based Velocity Measurements of a Magnet in a OFHC Tube

Abstract

When a permanent neodymium magnet falls through a conductive tube, its motion induces eddy currents due to change in magnetic flux. According to Faraday's Law, these currents are generated within the conductor, and according to Lenz's Law, the resulting magnetic field opposes the change that produced it. This interaction creates a retarding force known as magnetic braking, causing the magnet to descend at a reduced terminal velocity.

This poster explores the reasons behind the differences in the terminal velocity of different neodymium magnets falling through a tube of oxygen-free high-conductivity (OFHC) copper. An Arduino-based data acquisition system using photoelectric sensors and a hall effect sensor measured drop times and magnetic field strengths for multiple magnet geometries. The measured terminal velocities were then compared with theoretical values to quantify the effects of field direction and strength.

The results indicate that both geometry and field strength affect terminal velocity. Magnets with stronger magnetic fields experienced greater magnetic braking and descended more slowly, while the nonmagnetic steel sphere exhibited negligible braking and the highest velocity. These findings agree with the theory of electromagnetic induction and provide further insight into how induced currents and the magnetic forces associated with them affect the motion of objects. This work deepens the understanding of magnetic braking, with potential applications in magnetic levitation rail systems and electromagnetic arresting systems.