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

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 produces a force, similar to viscous drag, on the falling magnet. 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.

Study of the effect of electromagnetic damping force on a magnet oscillating near a non-ferromagnetic conducting plate

“…Some of them have presented the experiments with a view to demonstrating Lenz's law [1][2][3][4][5][6][7][8][9]. The role of eddy currents in the damped falling motion of magnets inside conducting tubes [10][11][12][13][14][15][16] and in magnetic levitation [17] has also been investigated. Some other researchers have conducted detailed analyzes of EM damping [18][19][20][21].…”