Determination of the magnetic moment of a magnet by letting it fall through a conducting pipe

TL;DR

This paper introduces a low-cost, acoustic-based method to measure a magnet's magnetic moment by analyzing its free fall inside a conducting pipe, combining physics, electromagnetism, and acoustics.

Contribution

It presents a novel, cost-effective technique using sound resonance to determine magnetic moments through magnet fall dynamics in a conducting pipe.

Findings

Measured magnetic moments consistent with reported values.

Demonstrated the effectiveness of acoustic resonance in tracking magnet motion.

Validated the method with torsional oscillation experiments.

Abstract

A novel method is proposed to determine the magnetic moment of a magnet by studying its free-falling motion inside a non-ferromagnetic and conducting pipe. The dynamics of a neodymium magnet falling inside a pipe is tracked by using sound waves of a fixed frequency generated by one smartphone and detecting acoustic resonance in the pipe simultaneously by the other. This tracking technique leads to the measurement of the terminal velocity of the falling magnet, as the interaction between the magnet and the conducting pipe creates viscosity artificially. The result obtained is verified by studying torsional oscillations of the suspended magnet and conforms to the reported value in such a low-cost setup. The experiment is designed with concepts integrating the domains of general physics, electromagnetic induction, and acoustics.