Types of Magnets

You must have come across plenty of magnets in your daily life, some stuck on your walls, refrigerator, some on the cupboards, or in toys. Magnets are found in many other appliances around the house like the telephone and radio. Even our planet earth is one giant ball of magnet, that attracts us all to the surface.

Basically, there are two kinds of magnets: natural and man-made magnets. The natural magnets are rich in iron mineral and are called magnetite. Man-made magnets are made by processing metallic alloys to get the charges aligned.

Different Kinds of Magnets

There are four main types of magnets which have been listed below:

• Permanent magnets
• Temporary magnets
• Electromagnets
• Superconductors

Magnets and Their Uses

Magnets are those things which produce magnetic fields. They attract those objects which have opposite charges, and repel those that possess the same charge. That is why the saying goes as 'opposites attract'. The different types of magnets and their uses vary according to their composition and the field that they produce.

The following paragraphs will explain all about these types in detail.

Permanent Magnets

Of all the different kinds of magnets, the permanent magnets are most commonly used. They are those magnets that once magnetized can retain their magnetism. The most common use of this type of magnet is its use to hold notes and decorate the refrigerator door.

They are used as hooks, audio speakers, jewelry making, compass (for indicating directions), etc. The permanent magnets are further divided into various types based on their composition.

Neodymium Iron Boron (NdFeB or NIB)

These are really strong magnets that even half-inch diameter of a magnet is able to lift ferromagnetic objects weighing several pounds. These are the most expensive of all the existing types.

They are made up of rare earth magnetic materials which possess magnetic properties. Because of their high magnetic fields they are usually made smaller in size.

Samarium Cobalt (SmCo)

Similar to neodymium magnets, samarium magnets possess high magnetic strength and can be difficult to degauss. However, they are known to possess low mechanical strength. They have the ability to sustain temperatures as high as 300ºC and are resistant to oxidation.

Alnico

These type of magnets, as the name suggests, are made from aluminum, nickel, and copper.
They can be degaussed as and when desired. They offer resistance to a good range of temperatures. They are formed by either casting or sintering processes. They are also capable of taking a large variety of shapes.

Ceramic or Ferrite

These are strong magnets that are difficult to demagnetize. They are easy to produce and are made using the sintering process. However, care needs to be exercised while making them as they tend to be brittle. Thus, a tool containing diamond is used to grind them. They are moderately priced.

Temporary Magnets

The temporary magnets are those that act like permanent ones only when they are within a range of a strong magnetic field. As soon as they are removed from the field, they lose their magnetism.

The objects that act as temporary magnets are paperclips, iron nails, etc. These type of magnets are used in telephones, electric motors, even in the production of electricity, etc.

Electromagnets

The electromagnets are the ones that are a tightly wound coil of wire. When current flows through the coil of wire (usually with an iron core), it acts like a permanent magnet. It is easy to change the strength and polarity of the magnetic field of these magnets.

This can be done by changing the magnitude of the current flowing through the wire and changing the direction of electric charge. The uses of these variety include large cranes, lifting cables and rods during construction, television, computers, radios, video tapes, speakers, etc.

Superconductors

The superconductors are the strongest amongst all the magnets. These magnets are also made of wire coils of special metal alloys without a metal core. These metal alloys become superconductors when they are cooled at very low temperatures.

The superconductor magnet uses include Magnetic Resonance Imaging (MRI) machines, NMR equipment, mass spectrometers, magnetic separation process, and particle accelerators, etc.

Sizes and Strength of Magnets

There are different types of magnets that vary in their size and shape. You could find tiny magnets that are used by the electronic industry and giant magnets that are used for cyclotron experiments. Even the strength of the magnets vary widely.

Simple magnets that stick to your refrigerator have about one tenth of tesla strength. The U.S. Department of Energy's Berkeley Lab in 2001 built an electromagnet to bend the paths of high-speed atomic particles. The strength of this magnet was 14.7 tesla, the strongest in the world.

Examples of Commonly Used Magnets

Horseshoe magnet

It is a magnet that is U-shaped, which remains magnetized. The advantage of this magnet is that both its magnetic poles (N and S) are parallel to each other and facing the same direction.

Bar magnet

A magnet which has the shape of a rectangular bar is called a bar magnet. Its two ends depict the north and the south pole, respectively. This is a permanent magnet as it remains magnetized at all times.

Round magnet

A magnet having small size and a rounded shape is called a round magnet. This usually has a hole at the center. It is used in holding small-sized objects such as a knob, earring, or a hook.

Magnets have been used for over thousands of centuries by sailors to find their way around at seas. William Gilbert, in the early 1600s, began studying the magnets to prove that the earth too had magnetic properties and one could change magnetism by external methods.

Since then, studies of magnets have helped in many useful inventions, which has come to the aid of mankind immensely.