Levitated Homopolar Motor

摘要

Anumber of homopolar motors ave been described in this jour-nal and elsewhere.~(1-9) The new onedescribed here has some very interest-ing features. Its construction is shownschematically in Fig. 1. Neodymiummagnets (disks 1.5 cm in diameterand 0.5 cm thick) are placed at theends of a AA battery. An aluminumfoil tube (-1.6 cm diameter) is madeby wrapping a piece of foil (-6 cm x15 cm) around a whiteboard marker.The tube is slightly longer than themagnet-battery array. When thehighly conducting tube is positionedaround the array as shown, it mo-mentarily short circuits the battery.The magnetic force on the flowingcurrent results in a torque that causesthe tube to rotate. Faint sparks canbe observed between the tube andthe magnets; the instantaneous cur-rent can be more than 8 A. Becauseof this, we prefer using a rechargeableNiMH battery due to its good perfor-mance for high drain. Occasionallythe magnets can get too hot to betouched.