Magnets are materials which can exert a force on other materials without coming in physical contact with them. This exerted force is called magnetic force, which can either attract or repel. Although all objects exert a magnetic force, it is negligible compared to that of true magnets. In fact, the Earth itself is a magnet.
The Greeks were the first to systematically study magnets, way back in 500 B.C. The word “magnet” was derived from the Greek name “Magnetis Lithos”. Lodestone, or magnetic iron ore, was the magnet of choice for Europeans, and it was used as a compass from 1100 to 1200 AD. The term “lodestone” means “leading stone” in Anglo-Saxon.
It was not until the 17th century that English scientist William Gilbert started researching the properties of lodestone, and he published his findings in the significant De Magnete. He claimed that the Earth is a magnet, which was contrary to the accepted belief at that time. He further stated that a magnet's polarity is comparable to the polarity of the Earth. Taking the knowledge of magnetism further was the Dutch scientist Hans Christian Oersted, who discovered the relationship between electricity and magnetism in 1820.
At the turn of the 20th century, scientists began studying magnetic materials which were not iron and steel. This led to the development of the powerful Alnico alloy permanent magnet in the 1930s, and subsequently, the even more powerful ceramic magnets which were created in the 1970s.
Magnets can be divided into several types. Certain magnets are called permanent magnets. These magnets will continue exerting a force without any outside assistance. Lodestone or iron ore magnetite is one such example. A magnetite is an iron oxide that has natural magnetic abilities. Certain materials can be transformed into a permanent magnet by subjecting them to a magnetic force. Even when the magnetic force is removed, the magnetic properties are retained; hence, they become permanently magnetized. On the other hand, temporary magnets act like permanent magnets when they are subjected to a strong magnetic force. However, when the magnetic field is removed, they will lose their magnetic properties. Some common examples of temporary magnets are paperclips, nails, and certain soft iron materials.
Electromagnets are created when a certain material is surrounded by a coil and electric current is passed through the coil. As a consequence, the material develops magnetic properties. However, when the current is shut off, its magnetic properties are eliminated too. A superconducting magnet is a type of electromagnet which is created using a special type of coil called superconducting coil. Superconducting magnets can be made of niobium-titanium outer sections and niobium-tin inner sections. They are used in magnetic separation, nuclear magnetic resonance for chemical analysis, particle accelerators, and magnetic levitation.
A magnetic force field refers to the region around a magnet that acts on a moving charge or another magnet that is placed in the force field. There are two points in a magnet called the magnetic poles, where the force field is the greatest. One is called the north seeking pole while the other is called the south seeking pole. The rule of magnetism states that 'like' poles will repel and 'unlike' poles will attract. The earlier version of the compass, which was the lodestone, was suspended from a string by sailors. The north seeking pole would automatically point north, towards the North Pole. This allowed sailors to navigate in the sea and return home without losing their way. Terrestrial magnetism is the science which is concerned with the study of the Earth’s magnetic phenomena and the Earth’s magnetic force.
Magnets have become an indispensable part of people’s lives. Presently, many types of magnets, like magnetic conveyors, plates, separators, pulleys, and grates, are used in industries. They are even used in medical science in the form of X-Rays and MRI (magnetic resonance imaging). Even the electrical appliances that we come across in our daily lives, such as televisions, video tapes, computer hard drives, and credit cards, contain certain types of magnets.
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Magnets have truly come a long way since the days when they served as compasses -- to the present day when magnetic levitation is being incorporated in Maglev trains. Without a doubt, magnets will keep contributing to various human endeavours in the future.