ball away from the magnets. If the track is not constructed carefully a slight imbalance can send the steel ball off the track into one of the magnets. Analysis of operation At the starting point, the ball has the potential energy given it by being put there under the forces of the magnets. When the ball is released, the potential energy is converted to kinetic energy as the ball rolls up the track and drops off the top. The sum of kinetic energy and potential energy is always constant (minus energy lost due to friction). The ball never has more energy than it did when first put into position. The magnetostatic field produced by any arrangement of stationary permanent magnets is a conservative field of the magnetic scalar potential. This means any magnetic object which moves in a closed-loop path in the field, like the ball in this device, gains no energy from the field, and in the absence of friction ends with the same total energy (kinetic plus potential) it started with. Since any moving object is also subject to friction forces, which dissipate the kinetic energy as it moves, the ball will always end a cycle with less energy than it started with, and will eventually stop moving. References 1985 introductions Perpetual motion Fictional power sources