Horseshoe magnet

A horseshoe magnet is a magnet made in the shape of a horseshoe. At the ends of its legs, the magnet has two magnetic poles close together. This shape creates a strong magnetic field between the poles.

This article is about objects and devices that produce magnetic fields. For a description of magnetic materials, see Magnetism. For other uses, see Magnet (disambiguation).
Horseshoe magnet with computed magnetic field lines. The two magnetic poles are in close vicinity, which concentrates the field lines and creates a strong magnetic field.

It is one type of permanent magnet, meaning that it stays magnetized, as opposed to an electromagnet, the magnetic field of which can be started and stopped.[1]

The purpose of a horseshoe magnet's shape is to place the poles as close together as possible.[2] The total magnetic flux is the same,[lower-roman 1] 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.

A horseshoe magnet can be created by bending a bar magnet into a horseshoe shape.[2][3]

  • A horseshoe magnet made of alnico, an iron alloy. The strong magnetic field between the poles allows the magnet to pick up a heavy piece of iron.
  • Magnetic field of a horseshoe magnet. The field is greatest where the lines are densest, around the poles (lower)
  • Alnico horseshoe magnet used in a magnetron tube in an early microwave oven. About 3 in (8 cm) long.
  • Assortment of Alnico horseshoe magnet shapes available from a manufacturer in 1956.

Notes
  1. This flux depends on the amount of magnetised material.
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    References
      1. "What is a Horseshoe Magnet? (with pictures)". wiseGEEK. Retrieved 2016-11-16.
      2. Lynette, Rachel (2008). Magnets: Magnetism. Heinemann-Raintree Library. ISBN 9781432910976.
      3. Giordano, Nicholas (2012-07-27). College Physics: Reasoning and Relationships. Cengage Learning. ISBN 1285225341.


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