Editing Halbach array (section)

===Varying the field===
Halbach cylinders give a static field. However, cylinders can be nested, and by rotating one cylinder relative to the other, cancellation of the field and adjustment of the direction can be achieved.<ref>{{Cite web |url=http://www.tipmagazine.com/tip/INPHFA/vol-4/iss-3/p34.pdf |archive-url=https://web.archive.org/web/20060328054612/http://www.tipmagazine.com/tip/INPHFA/vol-4/iss-3/p34.pdf  |title=Tip Magazine: Magnets, Markets, and Magic Cylinders The Industrial Physicist by Michael Coey and Denis Weaire |archive-date=28 March 2006}}</ref> As the outside field of a cylinder is quite low, the relative rotation does not require strong forces. In the ideal case of infinitely long cylinders, no force would be required to rotate a cylinder with respect to the other.

[[File:Halbach_planar_array.svg|thumb|Magnetic levitation using a planar Halbach array and concentric structure windings|220x220px]]