The purpose of a horseshoe magnet's shape is to place the poles as close together as possible. The total magnetic flux is the same,[i] but the field is greater, as it is spread over a smaller volume. A horseshoe is used, rather than a simpler C-shaped magnet, which is also used, because this places the maximum amount of magnetised material into the magnet, for given dimensions around the poles. A particularly large horseshoe magnet is U-shaped with long parallel sides, rather than the classical horseshoe.
Electromagnets are also constructed as horseshoes. They may have either one or two coils wound on them. As most coils are wound by machine, the coil formers are straight. They are thus usually placed as two coils, one on each side of a U-shaped horseshoe.
Alnico horseshoe magnet used in a magnetron tube in an early microwave oven. About 3 in (8 cm) long.
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