Types of Magnets Quiz

Types of Magnets

• Magnets are either natural or artificial.
• Artificial magnets are divided into permanent magnets, which retain their magnetism after removing the magnetizing force, and temporary magnets, which lose their magnetism quickly after the magnetizing force is removed.
• Modern permanent magnets are made from special alloys (e.g., Alnicos, Ferrites, Neo magnets, and Samarium-Cobalt) which are created through research and development.
• Alnico is considered one of the best permanent magnets because it is an alloy of iron, aluminum, nickel, and cobalt.
• Other alloys with high magnetic properties include Remalloy™ and Permendur™.
• The retentivity of a magnet is determined by the type of metal and indicates how well it retains its magnetism.
• Soft iron is easily magnetized but loses most of its magnetism quickly. The remaining magnetism is called residual magnetism, and it is essential for electrical applications, such as generator operation.
• Steel is magnetized in a magnetic field created by a solenoid and retains its magnetism after the field is removed.

Horseshoe Magnets

• Horseshoe magnets are commonly manufactured in two forms: a long bar curved into a horseshoe shape, and two bars connected by a third bar (yoke).

Magnetic Material

• Materials like soft iron and ferrous metals have high permeability, indicating the ease with which magnetic flux can penetrate a material.
• Permeability is measured on a scale based on a perfect vacuum with a rating of one.
• Air and nonmagnetic materials have a permeability rating close to one.
• Paramagnetic materials, such as nickel and cobalt, have a permeability greater than one.
• Ferromagnetic materials, like iron and its alloys, have the highest permeability.
• Diamagnetic materials, such as bismuth, have a permeability less than one.

Types of Magnets

• Magnets come in various shapes, such as balls, cylinders, or disks.
• Ring magnets, or Gramme rings, are closed loop magnets often used in instruments and have no poles.

Magnetic Quantities

• Magnetic field "H" refers to the area around a magnet or coil where its influence is felt. The field lines move from the north pole to the south pole outside the magnetized material. It is expressed in A/m.
• Magnetic Induction field "B" refers to the value of a magnetic field at a specific point in space. Its value depends on the shape and material of the magnet.
• B = 𝜇0.𝜇𝑟.𝐻 (where B is in Tesla T, 𝜇0 is vacuum permeability, and 𝜇𝑟 is relative permeability).

Properties of a Magnet

• They attract ferromagnetic materials like iron, cobalt, and nickel.
• Like magnetic poles repel, while unlike poles attract.
• Lines of force from like poles do not cross, and they turn aside as the poles are brought together, causing mutual repulsion.
• A freely suspended magnet always aligns in a north-south direction.
• A magnetic pole cannot be isolated.
• Magnetization can be permanent or temporary.
• Breaking a magnet creates two new magnets, each with a south pole and a north pole.
• Between two poles of a horseshoe magnet, a uniform field exists.