PROBLEM TO BE SOLVED: To provide a spontaneously rotating top with which a strange phenomenon in unipolar induction is easily demonstrated and which is suitably used for a scientific education material or a scientific education toy, and to provide its rotation method.
SOLUTION: The top 1 includes: a rotation shaft 2 having conductivity; a conductive rotor 3 which has a circular transverse section and is fixed concentrically with the rotation shaft so that the rotation shaft penetrates the center of the rotor vertically; and permanent magnets 4, 5 which are integrally rotated with the rotation shaft and the rotor so as to generate a magnetic flux penetrating the rotor in an axial direction. A direct current is made to flow in a radial direction at a part between the outer circumferential side of the rotor and a rotation shaft side in a state that the spontaneously rotating top is initially rotated on a conductive support surface. Consequently, the rotation speed of the top increases without affecting the ambience by a reaction torque, so that the strange and interesting phenomenon is experienced and investigated.
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