A horseshoe magnet is a U-shaped metal object that produces a magnetic field. This magnetic field in invisible, but is responsible for a magnet’s notable pull on other metal objects. It is one type of permanent magnet, meaning that it stays magnetized, as opposed to an electromagnet, whose magnetic field can be started and stopped.

Originally, the horseshoe magnet was made as an alternative to the significantly weaker bar magnet. Its lifting strength is doubled, compared to that of a bar magnet, because both of its magnetic poles point in the same direction. For industrial applications, they have largely been replaced by even stronger magnets, but are still effective for uses such as classroom demonstrations and picking up small metal objects.

Horseshoe and U-shaped magnets come in every size and lifting strength, at prices that are equally varied. Properly kept, they can hold their magnetism for decades. They are common enough that a red U-shaped magnet is the universal symbol of magnets, recognized around the world.

Definition provided by Wise geek