The magnet is a natural permanent magnet. Other permanent magnets can be made by subjecting certain materials to a magnetic force. When the force is removed, these materials retain their magnetic properties. They are made by surrounding certain materials with a coil of wire. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay The first thing made with the magnet was a compass. It is believed to have occurred in Europe between 1100 and 1200 AD. All magnets have two points where the magnetic force is greatest. These two points are known as poles. For a rectangular or cylindrical bar magnet, these poles would be at opposite ends. One pole is called the north search pole, or north pole, and the other pole is called the south search pole, or south pole. This terminology reflects one of the earliest uses of magnetic materials such as the lodestone. When suspended from a string, the north pole of these early crude compasses always sought or pointed north. These permanent magnet magnets contain magnetite, a hard, crystalline iron ferrite mineral that derives its magnetism from the effect the Earth's magnetic field has on it. Various steel alloys can also be magnetized. The first major step in the development of more effective permanent magnetic materials came in the 1930s with the development of Alnico alloy magnets. These magnets are named after the chemical symbols of the aluminum-nickel-cobalt elements used to make the alloy. Once magnetized, Alnico magnets have between 5 and 17 times the magnetic strength of lodestone in judging the direction to go to distant lands and back home. In the 1970s, researchers developed permanent magnets made from hot-melted samarium-cobalt powder. Just as the materials are different for different types of magnets, the manufacturing processes are also different. Many electromagnets are cast using standard metal casting techniques. Flexible permanent magnets are formed in a plastic extrusion process where materials are mixed, heated and forced through a shaped opening under pressure. Electromagnets: The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be changed quickly by controlling the amount of electric current in the coil. However, unlike a permanent magnet which requires no energy, an electromagnet requires a continuous supply of current to maintain the magnetic field. An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is interrupted. Electromagnets are usually made of insulated wire wound into a coil. A current flowing through the wire creates a concentrated magnetic field in the hole in the center of the coil. The coils of wire are often wrapped around a magnetic core made of a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and creates a more powerful magnet. Starting in 1830, American scientist Joseph Henry systematically improved and popularized the electromagnet. Using a wire insulated from silk thread and inspired by Schweigger's use of multiple turns of wire to make a galvanometer, he was able to wind multiple layers of wire onto the cores, creating powerful magnets with thousands of turns of wire, including one capable of supporting 2,063 pounds (936 kg). The first major use of electromagnets was in telegraph sirens. Please note: this is just an example. Get a customized document from our writers now.