Magnetic Repulsion: An Introductory Experiment

Abstract

To measure the repulsion between two bar magnets gives students direct experience of action at a distance and of an inverse square force. This can be done using a balance assembled from standard laboratory components. The results are analyzed by assuming an interaction between two fixed poles located near the ends of the magnets, the force between them varying inversely with the square of the distance. The theory can be extended to cover all the interactions of the two pairs of poles. Calculations from the extended theory show that within the useful range of the experiment there are no induction effects and the poles do remain fixed. Although these theories are inconsistent with the usual presentation of electromagnetic forces arising from the interactions of charges, the experiment is useful as an illustration of model-building in physics.

Design and control of a new linear magnetic actuator for squeeze film damper

“…where B 0 is the magnetic flux density very close to each pole, T A is the area of each pole, m 2 L is the length of each magnet, m R is the radius of each magnet, m x is the gap between two magnets, m by Defrancesco and Zaneth (1983) and Romer (1973) are rewritten in Eqs. (2) and (3) as follows*:…”

“…In [10,11], these impact the experimental studies using permanent magnets and an air track to illustrate dipole-dipole interactions and mechanical stability. Other researchers [12,13] investigated the repulsion between two bar magnets which led to the relationship between the distance and the repulsive force. In fact, the interaction force between the two charges is directly proportional to 1/r 2 , 1/r 3 , and 1/r 4 with respect to monopoles, monopole-dipole, and dipole-dipole, respectively.…”

Measuring the Forces Between Magnetic Dipoles

“…[1][2][3] We wish to suggest an approach that requires only very basic equipment, allows one to also measure the force between a permanent magnet and a small piece of a ferromagnetic material, and gives extremely good agreement with theoretical expectations for the distance dependence of the magnetic force.…”

Experiments and models about the force between permanent magnets: asymptotic analysis of a difficult problem

“…Many researches in last decades has shown how experimental activities are significant sources of knowledge in the physics teaching/learning practice, since they offer students the chance to contextualize abstract concepts and to challenge their naïve beliefs [1][2][3].In the case of electromagnetic phenomena, the main difficulties encountered by learners are clearly identified in the literature [4][5][6][7] and in recent years several studies were published focusing on experimental activities as a means to enhance students' conceptual understanding [8][9][10][11][12][13][14][15]. Authors have proposed in the past a number of experiments on the magnetic interaction between permanent magnets; e.g.…”