Stable levitation of ring magnets: A low-cost, 3D-printed experiment on the magnetic force-distance law

Abstract

Magnetic levitation is one of the most captivating phenomena in physics, combining a striking visual appeal with the rich underlying physics of forces and interactions in equilibrium. Bringing it into undergraduate laboratories in a quantitative way is nevertheless often hindered by the intrinsic instability of static magnetic systems and by the high cost of active control systems. Here we present a simple, safe, and very low-cost experiment that uses ring-shaped ferrite magnets together with a mechanical stabilization system fabricated by 3D printing in a male--female configuration. The apparatus lets undergraduate students explore directly and quantitatively the relationship between the magnitude of the magnetic force and the separation distance. We assess the robustness of the device through experimental tests, whose results show excellent quantitative agreement with the equivalent current-loop model. Furthermore, we validate this model through a complementary, independent first-principles-based methodology based on axial magnetic field profiling. To support reproducibility, the 3D design files are made available in a public, open-access repository.