Weighting magnetic interactions

摘要

The use of toys in physics teaching is common practice [1–3] because a lot of physics may be demonstrated with them, if properly employed. In particular, there is a well known toy that provides many insights into magnetic-field properties: the Geomag magnetic building kit. This kit consists of a number of strong cylindrical bar magnets (6 mm in diameter and 25 mm in length, completely covered in hard plastic except at their two ends) and of a number of ferromagnetic steel balls (12.7 mm in diameter). Geomag kits have been used in the past for educational purposes either to elucidate qualitatively some magnetic force/torque [4] and field [5] issues, or as a tool for the practical illustration of the well-known ‘method of images’ in electrostatics by establishing analogies between electric and magnetic phenomena [6].