**2.1. Principle of magnetic drive**

The explanation shows the magnetic drive principle by use of floating magnetic fluid and a simple magnetic field.

Fig.1 shows the schematic diagram of the rolling object that is driven by the proposed magnetic drive principle. The functional section(1) and the liquid(2) are sealed in the interior by the outer cover(3).

The inner wall(4) and outer wall(5) of the outer cover are covered with the small projections or a textured material. The projections play the role of creating friction. Floating magnetic particles(6) are employed in a magnetic field. The specific gravity of these magnetic particles is smaller than the liquid, so they gather in the upper part of the rolling object when no magnetic field is applied.

When a magnetic field is applied, the magnetic particles move in the direction of the magnetic field quickly. The path they take is just inside the outer cover, because both the magnetism and buoyancy are working on the magnetic particles. The particles collide with the projections on the inner wall of the outer cover (Fig. 1(b)).

The external side of the outer cover does not slip on the ground, because there is friction between the ground and the outer wall. Consequently, the rolling object moves in the direction of the magnetic field (Fig. 1(c)). After the magnetic field is removed, the magnetic particles will return to the upper part of the rolling objet slowly (Fig. 1(d)), the rolling object stayed at the same position. By repeating the above, the rolling object can move a long distance.

If the specific gravity of a magnetic particle is larger than the liquid, the object rotates in the opposite direction (Fig.2). The movement becomes unstable because it may move in the opposite direction to the magnetic field.
