A homopolar motor is a direct current (DC) electric motor which produces constant circular motion. This device is easy to create and the figure below illustrates the basic concepts behind its operation. A permanent magnet is attached to one terminal of a DC power supply, in this case a AAA battery. A conducting wire connects the other terminal to the magnet, thus completing the circuit. This wire should be free to rotate whilst always maintaining contact with both the terminal and magnet. The...

A Halbach array is a specific arrangement of a series of permanent magnets. The array has a spatially rotating pattern of magnetism which cancels the field on one side, but boosts it on the other. The main advantages of Halbach arrays are that they can produce strong magnetic fields on one side whilst creating a very small stray field on the opposite side. This effect is best understood by observing the magnetic flux distribution. Strips of ferromagnetic materials (materials which can be...