Horseshoe magnet

A horseshoe magnet is a magnet made in the shape of a horseshoe or a U shape and has become the most widely recognized symbol for magnets. It was invented by William Sturgeon in 1825. This type of magnet can be either a permanent magnet or an electromagnet. The main advantage of a horseshoe magnet over other types of magnets is that the magnetic poles are close together creating a much stronger magnetic field.

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.
Magnetic fields of a horseshoe magnet visualized using iron filings.

HistoryEdit

In 1819, it was discovered that passing electric current through a piece of metal deflected a compass needle. Following this discovery, many other experiments surrounding magnetism were attempted. These experiments culminated in William Sturgeon wrapping wire around a horseshoe-shaped piece of iron and running electric current through the wires creating the first horseshoe magnet.[1]

This was also the first practical electromagnet and the first magnet that could lift more mass than the magnet itself when the seven-ounce magnet was able to lift nine pounds of iron.[1][2] Sturgeon showed that he could regulate the magnetic field of his horseshoe magnet by increasing or decreasing the amount of current being run through the wires.[2] This would lay the groundwork for development of the electrical telegraph and the future of world-wide telecommunications for the next century and more.[2]

ShapeEdit

The shape of the magnet was originally created as a replacement for the bar magnet as it makes the magnet stronger.[3] Over time it became the universal symbol for all magnets.[3] A horseshoe magnet is stronger because both poles of the magnet are closer to each other and in the same plane which allows the magnetic lines of flux to flow along a more direct path between the poles and concentrates the magnetic field.[4]

The shape of the horseshoe magnet also drastically reduces its demagnetization over time.[5] This is due to coercivity also known as the "staying magnetized" ability of a given magnet.[5] Coercivity is weaker in disc or ring shapes, slightly stronger in cylinder or bar shapes, and strongest in horseshoe shapes.[4][5] To increase the coercivity of horseshoe magnets, steel keepers or magnet keepers are used.[5] A magnetic field holds its strength best when the entire magnetic field is given the ability to loop through a ferromagnetic substance instead of air.[6] The nearness of the horseshoe magnet’s poles facilitates the ability to use these magnet keepers way more easily than other types of magnets.[6]

ReferencesEdit

  1. ^ a b "Magnetism and Electromagnetism". Spark Museum. SPARK Museum of Electrical Invention. Retrieved 3 January 2021.
  2. ^ a b c Bellis, Mary (23 February 2019). "William Sturgeon and the Invention of the Electromagnet". ThoughtCo. ThoughtCo. Retrieved 3 January 2021.
  3. ^ a b "The Various Shapes of Magnets and Their Uses". Apex Magnets. Apex Magnets. Retrieved 3 January 2021.
  4. ^ a b "Temperature and Neodymium Magnets". K&J Magnetics. K&J Magnetics, Inc. Retrieved 3 January 2021.
  5. ^ a b c d "Why are Magnets Shaped like Horseshoes?". K&J Magnetics. K&J Magnetics, Inc. Retrieved 3 January 2021.
  6. ^ a b "Demagnetizing a Steel Nail". Sciencing. Sciencing. Retrieved 3 January 2021.

External linksEdit