When you were young, you may have remembered trying to make objects stick together or move things, like metal paperclips, just by using a magnet. Back then, you probably thought that a magnet only existed in this form. But, now that you’re older, you’ve realised that this object plays a significant role in day-to-day life.
Indeed, everything that works around you makes use of magnets and the magnetic field. Although you cannot see it, you can be aware of it—if you observe your surroundings. Magnets can be found in the simplest or the most complex devices you employ every day. From your home appliances like refrigerator, microwave oven and electric fan, to your business office equipment like computers and printers—all of these devices make use of magnets.
What is a Magnet?
A magnet is a solid object, usually made of iron, boron, neodymium or ferrite compounds, which has the ability to attract other materials (e.g., iron, steel,) within a magnetic field.
The Magnetic Field
A magnet has an invisible field that forces other objects to respond to its properties. This powerful force, which is referred to as the magnetic field, has particles called electrons that actively shift and move within the field. These electrons constantly revolve around the poles, thereby creating energy that attracts objects. Because of this, a magnet has the ability to draw objects towards itself. This ability, which is called magnetism, is caused by the force field that magnets create through its protons (positive charge) and electrons (negative charge).
A magnet also has two poles, called the north pole and the south pole. Although these poles appear the same, they act differently. If two magnets are close together, you will observe that contrasting poles attract each other, while like poles repel each other. For example, if you place the north pole of a magnet beside the south pole of another magnet, they will stick together. However, putting two magnets either north poles (or south poles) together will cause them to react the same way, thereby forcing them apart.
The Types of Magnets
Magnets also come in different sizes and shapes and can be classified into three types: temporary, permanent or electromagnet. Each type of magnet plays a valuable role in day-to-day life.
1. Temporary Magnets
These magnets act like permanent magnets when they are within the range of a strong magnetic field. But they tend to lose their magnetism once the magnetic field disappears. Common examples of temporary magnets are nails, paper clips and other soft iron items. Temporary magnets are generally used in electric motors and telephones.
2. Permanent Magnets
These magnets, which are made from ferromagnetic materials, create their own magnetic fields and react to other magnetic fields. Permanent magnets are those that people frequently use and interact with in their daily lives. They are known as permanent magnets because once they have been magnetised, they retain their magnetism. The following are the various types of permanent magnets.
- Ceramic (Ferrite) Magnet – is made by pressing and sintering compound of iron oxide and barium or strontium carbonate. Ceramic is the most widely used type of permanent magnet since it is inexpensive and easily manufactured. This magnet can be found in food processing industries and magnetic resonance imaging.
- Alnico Magnet – is produced by combining multiple elements like nickel, aluminium and cobalt with small amounts of other metals like titanium, copper and iron. Although alnico has good temperature stability and is capable of producing strong magnetic field, it can easily be demagnetised. This type of permanent magnet is commonly used in automotive and electronic sensors, actuators, magnetrons and reed switches.
- Samarium Cobalt (SmCo) Magnet – is a type of rare earth magnet that is highly resistant to oxidation and temperature, withstanding up to 300 degrees Celsius. This type of permanent magnet has higher magnetic strength; however, it can be expensive. Samarium cobalt magnet is used in high-end electric motors, turbo machinery, marine and medical equipment.
- Injection Moulded Magnet – is made by mixing magnetic material with a polymer binder (usually nylon or polyphenylene sulfide). One of the advantages of using injection moulded magnet is that it has a high degree of shape complexity. This means that it can be used to create simple to very complex shapes, thereby opening a way for engineers to create new design possibilities.
- Flexible Magnet – is created by combining rubber polymers and plastic with magnetic powders. This magnet is similar to the injection moulded magnet; but, it is produced in flat strips and sheets. Flexible magnets are used as door seals for refrigerators as well as to remove signage for motor vehicles.
- Neodymium Iron Boron (NdFeB) Magnet – is a type of rare earth magnet that has similar properties as samarium cobalt, except that it is more easily oxidised and doesn’t have the same temperature resistance. Although it is expensive compared to other magnets, neodymium magnet is popularly used in various industries (e.g., water conditioning, jewellery-making, book-binding and packaging) since it is seven times stronger than ceramic magnets and offers good temperature stability.
These magnets are produced by placing a soft metal core (commonly an iron alloy) inside a coil of wire through which electric current passes in order to produce a magnetic field. The strength and polarity of the magnetic field changes depending on the magnitude of the current flowing through the wire and the direction of the current. While there is sufficient flow of current, the core behaves like a magnet; however, as soon as the current stops, the magnetic properties also disappear. Modern devices that make use of electromagnets are the televisions, telephones, computers and electric motors.
The various types of magnets are used in countless facets in everyday life. Thousands of industries, including automotive, electronics, aerospace, craft, manufacturing, printing, therapeutic and mining utilise magnets so that their tools and equipment can properly function.
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By Debra Wright
Debra Wright is a creative online writer who supplies cyberspace with interesting and informative write-ups about her favourite topics including technology. A wide reader and ardent web surfer, she believes she can do anything as long as she has an Internet connection. Follow Debra on twitter @debrawrites…