Magnetism refers to a group of natural phenomena in which certain metals display a propensity for attraction. These metals can be naturally occurring in rock formations, or can be created through a variety of means, including electrical and nuclear.
Magnetic properties were first clearly discovered and written about as early as AD 20, when an ancient Chinese observer noted that lodestone-which contains iron-attracted other metal objects, namely a needle. However, Aristotle described the properties of magnets to a contemporary of his, even if he didn't have the right terminology or the correct principles behind the science. An eleventh century Chinese observer, Shen Kuo, later was the first known person to liken magnetism to its potential for more accurate navigation with the use of a rudimentary needle compass.
There are two chief sources of magnetic behavior, both of which are used to some degree in the creation of "permanent" magnets, the objects that most of use in some form on a daily basis.
1. Daily Use - Many individuals use magnets practically every day for basic adhering functions. Whether it's sticking an important piece of paper to a refrigerator or closing a purse for more security, there are daily purposes that make our lives easier.
2. Medical magnets - Magnetic resonance imaging, or MRI, is a process that allows doctors to "see" inside an individual to determine a diagnosis, decide if surgery is necessary, and more. Unlike an X-ray that shows almost exclusively the skeletal system, MRI allows doctors to see muscles, tendons, ligaments, and more with some degree of clarity.
3. Veterinary magnets - Grazing livestock have a bad habit of accidentally ingesting metal objects, especially in areas where water washes through the land and leaves deposits of garbage behind. These items, like nails and pieces of barbed wire fence, can seriously injure or kill a farm animal, and do so while causing excruciating pain. Veterinarians have learned to feed a large animal a powerful magnet that will attract the metal foreign object and help guide it out through the animal's excretory system.
4. Electromagnets - These magnets usually involve a coil of wire wrapped securely around a metal object, connected to a power source. This type of magnet can therefore be "turned on" or "turned off," which is an especially useful feature in lifting or transporting large objects, such as with an electromagnetic crane. Electromagnets are also used in communication, specifically in telephones.
5. Data storage - The magnetic strip has long been used in data storage, and a common example is the information stored via a strip on the back of a credit card. This strip stores information by rearranging the particles on a piece of magnetic material.
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