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Magnets have intrigued people for a long time; they were discovered long ago. Certain rocks and ores of iron called lodestones were found. These lodestones which were naturally magnetic rocks made of the mineral magnetite, were so mysterious to people that they caused many superstitions about themselves. One superstition was the belief that there were enormous lodestones rising out of the sea. Many sailors would not venture too far from land, believing that if they came too near one of these mountains the iron nails might be drawn out of their wooden ships. Another superstition about magnetism is an ancient Chinese legend that tells a tale about an Emperor Hwang-ti, who lived around 2600 BC. The story says that during a battle he was surrounded by thick fog. He managed to find his way through the thick fog by following a small pivoting figure with an outstretched arm attached to his chariot. The figure always pointed south because it had a loadstone embedded in its outstretched arm. Although it isn’t known if this story is true, most scholars agree that the first compasses were made by the Chinese. The fascination people have for the mysterious lodestone has continued for centuries. The earliest investigators of magnetism regarded magnetic attraction as the main property of a magnet. They either ignored or were unaware of magnetic repulsion. Lucretius (99-55 BC), a roman poet and philosopher, was one of the first to observe that a loadstone or magnet stone could both attract and repel other magnets. For about thirteen hundred years after Lucretius, scholars insisted that certain magnets possessed the property of attraction while others possessed the property of repulsion. To their minds, it did not seem possible that the same magnet could both attract and repel other magnets. Gradually it became evident that the two ends, or poles of a magnet are unlike in certain respects. Roger Bacon (1210-1294), an English philosopher and scientist pointed out that magnets could repel as well as attract other magnets. In 1600, William Gilbert, an English doctor, proposed that the earth was like a giant magnet. He had been experimenting with round pieces of magnetite and magnetized needles when he realized that the magnetite was attracting the needles in a way similar to the earth’s attraction of a compass needle. William Gilbert was also the first to call the ends of the magnets poles. William Gilbert's idea that the earth is a giant magnet turned out to be basically true. The earth is thought to obtain its magnetism from electricity made by molten iron and nickel sliding around inside it. The Earth’s magnetism is centered at an area in northeastern Canada by the North Pole (another center is by the South Pole). The needle of a compass points not to the top of the earth but to the magnetic north pole off to the side. The ends of a magnet are named after the north and south poles of the earth. The actual words north and south are just handy names a scientist gave the different ends long ago so he could talk to people about them. Scientist’s idea of what causes magnetism can best be explained by first saying that all things are made up of tiny particles called atoms. If you could look at the atoms in a piece of iron, which is what is used to make magnets, you would see that they are made up of even smaller particles. Atoms have a nucleus, which is made up of particles called protons and neutrons. Charged particles called electrons move around the nucleus. When electrons move they produce small magnetic fields. Usually electrons come in pairs. These pairs move in opposite directions and their magnetic fields cancel each other out. A piece of iron has a large number of unpaired electrons. In iron, the atoms align their magnetic fields with those of nearby atoms to form small magnetic areas called magnetic domains. When the domains are arranged randomly, in a piece of iron or another magnetic material, the material is not magnetized. When the magnetic material is placed in a strong magnetic field, the domains line up. The north poles of the domains all face in one direction, and the material acts as a magnet. Scientists have also noticed a link between magnetism and electricity. In 1820, a Danish scientist named Hans Christian Oersted made an amazing discovery. He found that when he placed a compass near a piece of wire that had electricity running through it, the compass needle changed direction. This showed that electricity and magnetism were related. Soon after Oersted’s discovery of the relationship between electricity and magnetism, French scientist Andre Marie Ampere began performing a number of experiments based on Oersted’s work. He found that when a wire carrying an electric current was bent into a loop, the magnetic force around it seemed to become stronger. Then he wound the wire into a coil and found that the coil acted like a bar magnet. He showed that a piece of iron inserted in the coil became strongly magnetized. Other scientists tried different ways to make magnets stronger. By the 1830s, they were able to make an electromagnet that could lift over a ton of iron. Another important discovery made by scientists regarding the connection between magnetism and electricity was that by Michael Faraday (1791- 1867) an English physicist. His ideas of electrical induction led the way to the development of electric generators (machines that convert mechanical power into electrical power). He created the first electric generator, which made it possible to manufacture a steady controlled flow of electricity. This led to many new discoveries such as the radio, the telegraph, street lights, and the phonograph. Some basic information about magnetism that you need to know to understand it is unlike poles attract and like poles repel. That means when you put a North Pole and a South Pole near each other, they will come together, but if you put two North poles or two South poles near each other, they will push away from each other. The greater the distance between two poles, the less force of attraction or repulsion. The greater the strength of the poles the greater the force with which the poles are drawn together or pushed apart. Another thing that many people don’t realize is that there is no place on a magnet without poles. The Molecular Theory of Magnetism states that a magnetized substance is made up of magnetized particles or tiny magnets that are lined up in an orderly fashion, that is, all the north poles face in one direction and all the south poles face the opposite direction. The magnetized particles in the middle of the magnet cancel one another’s effects because the north and south poles are adjacent to each other. The poles at the ends exert an effect on external objects because these end poles are not cancelled or neutralized. To go along with that theory that there are poles all throughout the magnet, if you were to break a magnet in half you would get two magnets, each with a north and south pole. You can not have a magnet with just a North Pole or just a South Pole; a magnetic pole of one kind is always accompanied by a magnetic pole of the opposite kind. Now that it has been established that a magnet can not have only one pole, you may wonder if it can have more than two poles. As a matter of fact it is possible for a magnet to have more than two poles; these other poles are called consequent poles. A magnet can have zero poles, two poles, four poles, six poles and so on. This pattern shows that the number of poles is always even, this is because poles always exist in pairs. The lifting power of a magnet does not depend on the number of poles, however, but the shape of the polar surface, the shape of the load to be lifted and the type of iron used in the load. The material used for permanent magnets has to process high retentivity and high coercivity. Retentivity is the ability of the material to retain much of its magnetism after the magnetizing force is removed. Coercivity is the power of resisting demagnetization. Every bar and horseshoe magnet tends to demagnetize itself to a certain extent. Magnets can be made by several different means. The prosess of making an unmagnetized object magnetized is called magnetic induction. The most powerful magnets are made by placing a bar of metal inside a coil of wire and then passing an electric current through the wire. This requires enormous currents of electricity; the more electricity used, the more magnetism surrounding the wire. You might wonder how long it takes before a magnet can’t become any further magnetized or if there even is such a point. The truth is there is a point at which this happens. It is said to be magnetically saturated which happens when the magnetism of all of its domains has been aligned parallel to the external field. At this time no further increase in magnetization can take place, no matter how much the external field is increased. Another method of making magnets is by using particles of iron. The particles have to be less than .000002 centimeters in diameter. This makes it so that each particle is small enough to be a domain. If the single domain particles are magnetized in the direction of their elongation, the shaped powders become magnetically stable. The manufacturing process consists of aligning the finely divided powder in an external magnetic field, pressing into required shapes, and firing at temperatures between 1000-1300 degrees Celsius. The different ways to make magnets make different types of magnets and magnetism. Some examples are electromagnetism, geomagnetism, residual magnetism, induced magnetism, diamagnetism, and ferromagnetism. Electromagnetism is the magnetism obtained by a direct electric current. Geomagnetism is the natural magnetism of the planet Earth, which acts like a giant magnet. Residual magnetism is magnetism retained by a magnetized object after a magnet is no longer near the object. Induced magnetism is the temporary alignment of the magnetic domains in a magnetic material that is placed near a magnet. Diamagnetism is the kind of magnetism that is in the opposite direction to the magnetic field. Finally, a substance that is ferromagnetic, such as iron or steel is strongly attracted to a magnet and can keep its magnetic charge. Magnets are also made out of different materials. The most commonly recognized material is steel. Special alloys of metals are used instead of just plain steel. The alloy provides domains that tend to remain in a line better than steel. One alloy made up of aluminum, cobalt, nickel, copper and iron, called Alnico is one of the strongest magnets available. Another material used is ferrite which is an earthy, ceramic material composed of iron oxide and the oxide of another metal such as nickel, cobalt or magnesium. These ferromagnets as they are called are magnetic even before they are placed in a magnetic field. They become noticeably magnetic when placed in a comparatively week magnetic field. Also, their ferromagnetism disappears when the material is heated above a certain temperature. This temperature is called the Curie temperature. There is a theory as to why some metals make better magnets than others do; this theory is called the electron theory of magnetism. This theory states that the electrons in each atom that make up the metal are believed to be spinning while revolving around the atom’s nucleus. Each electron spins around an axis through its center. In a magnetic substance like iron, more electrons spin in one direction than the other within each atom. In a nonmagnetic substance like copper or aluminum, the electrons spins cancel each other out; that is the spins in one direction are more or less compensated by spins in the opposite direction. So, in the iron, more electricity is produced, causing more magnetism. The space around a magnet is different from the space around an unmagnetized object. Michael Faraday (the same man who made the first electric generator) regarded the space around a magnet, called the magnetic field, as being in a state of stress. Because of this, a magnetic field exerts a force on any magnetic pole within its space. Lines of force are imagined as coming out from the north pole of a magnet and passing the south pole of the same magnet in a curved path. These imaginary lines are used to show the direction of the magnetic effect. The lines of force are most concentrated where the magnetic field is most intense. These are just some of the facts known about magnetism today. Hopefully it has now become clearer to you as to what magnetism is and where it originated. You also should understand now that magnetism had a lot to do with much of the technology that is present today and without it, this technology may never have even been thought of. Bibliography: Word Count: 2258
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