Imagine an elderly Cretan shepherd herding his sheep when suddenly the metal tip of his staff and the nails in his shoes become stuck to the black rock he is standing on. This is a popular theory as to how magnets were discovered, and the shepherd's name was Magnes. In order to figure out what was happening, he decided to dig up the earth where he had been standing and he discovered lodestones.
Magnetite is a natural magnetic material which is contained in lodestone. It is believed that magnetite is named after either Magnes or Magnesia (which was the area in Northern Greece where Magnes made his discovery). Either the Chinese or the Greeks are believed to have made the earliest discovery of lodestone properties. For many years after magnetite's discovery people believed it possessed magical powers such as the ability to heal the sick. People believed that entire islands were magnetic and attracted ships which contained iron nails. Disappearing ships at sea were believed to have been pulled to these islands by the strong magnetic force. Archimedes was believed to have used lodestones to remove enemy ship's nails in order to sink them. People soon made another discovery about magnetite. When it was made into a needle shape and floated on water, it always pointed north-south in direction. This created a primitive compass and a new name for magnetite which was lodestone (which means leading stone). The Mariner's compass was developed by the Chinese about 4500 years ago. It was a lodestone splinter which floated on water.
In 1600 William Gilbert conducted numerous experiments which led to a greater understanding of magnetism. Gilbert was the first person to realize that Earth was a huge magnet. He also is credited with discovering that a loss of induced magnetism would happen if heating occurred. In 1820 a man named Hans Christian Oersted showed how magnetism relates to electricity. He brought a wire which carried an electric current close to a magnetic compass. This caused the compass needle to swerve.
What Are Magnets?
Magnets are objects which create magnetic fields because of what they are made of and either attract or repel other objects. Magnets exert a large force on other materials when there is no contact between the magnet and the material. The force is called a magnetic force and it can either repel or attract objects. Each magnet consists of both a north and a south pole. The magnetic field lines exit a magnet's north end and go into the magnet's south end. No matter how many pieces you break a magnet into; there will always be a North and a South pole.
Magnets Are Made From What?
Magnets pull or attract iron objects. Not all metals are necessarily magnetic. Aluminum cans are made of a metal but do not contain iron. They are not magnetic. Steel is created from iron and is magnetic. Magnets contain certain metals including cobalt, nickel, iron or steel which when exposed to a magnetic field makes the metal magnetized. The molecules of the metal are rearranged by the magnetic field into a pattern of north-south.
How Do Magnets Work?
There are many different sizes, shapes and strengths of magnets. Every magnet has both a north and a south pole. If there are opposite poles (north and south) next to each other they will attract. If there are two of the same poles (such as north and north) next to each other they will push away from one another or repel. The pull of magnets goes through gases such as air. Depending on the magnet's strength they can also pull through liquids and solids. A magnetic field surrounds the magnet and it is where things are either attracted or pushed away. Only when an object enters a magnet's magnetic field can the magnet affect the object. The closer to a magnet the greater the strength of the magnet. The further away from a magnet the lesser the magnet’s strenth.
Common Uses of Magnets
Certain types of magnets keep many items in a home running, such as the washing machine and the cd player. Refrigerator and cabinet latches rely on magnets. The majority of magnets used in business and industry are electromagnetic powered devices such as cutters, cranes, computers and fax machines. Transportation can also be electrified and operated with electric motors. Subways, monorails, moving sidewalks, elevators, escalators, trolleys and cable cars are all examples of electrified transportation. Cars are more convenient because of electromagnets used in things such as door locks, windshield wipers and electric windows. Electromagnets are also very important in producing radio waves which are used in radar systems. These systems help planes and ships to navigate.
Magnets in the Medical Field
Have you or someone you know ever had an MRI? MRI stands for “magnetic response imaging.” During the early 1980's MRI's were beginning to be used in medicine. They are a safe way to produce images of the inside of the body. During an MRI the patient lays between two magnets. Doctors can then view magnetic fields that some of the organs produce. MRI's are very good at differentiating between normal, healthy tissue and damaged or diseased ones. They became better in providing organ images than the majority of other imaging techniques by the late 1980's.
For further information about magnets, see the following links: