Magnets attract iron, steel and cobalt. We use them in many different things: televisions, magnetic cassette tapes and VHS tapes, computer discs, ATM, debit and credit cards, doorbells, junkyard cranes and, of course, refrigerators. Magnets have a wide range of applications in technology, such as in particle accelerators (the Large Hadron Collider at CERN), electric motor, and magnetic resonance imaging machines (MRI). We even live on a magnet—Magnet Earth—with its north and south poles.
Magnets In General
Some magnets, lodestone and magnetite, occur naturally. Man-made magnets are made from iron, nickel or cobalt. You can magnetise an object yourself by stroking it repeatedly in one direction with a permanent magnet. Also you can wind a coil of wire around the object two or three times or more and then pass electricity through it. This is a basic electromagnet or a solenoid.
No matter how you create your own magnet, you are forcing the molecules to align themselves in a N-S orientation. It’s easy to destroy a magnet with extreme heat or by hammering on it, because that breaks up the orientation of the molecules so that they align themselves randomly and no magnetic force remains.
Types of Magnets
There are two basic types of magnets: permanent magnets and induced magnets. Permanent magnets are just that—permanent. These are lodestone and magnetite which occur naturally.
An induced magnet becomes temporarily magnetised when it is brought near a permanent magnet. For example, if you use a magnet to pick up nails, those nails become temporarily magnetised as long as they are in contact with the permanent magnet. They can pick up other nails themselves. But remove the permanent magnet. and the induced effect no longer works so that the whole conglomeration of nails falls apart.
The earth itself is a magnet. The motion of the molten iron circulating in the core of the planet creates a north pole partnered with a south pole. It explains why the earth is still geologically active. As the molten material circulates in the core, it creates heat due to friction. This heating sets up convection currents which rise to the earth’s crust and drive plate tectonics, which results in volcanic activity and earthquakes.
Magnets In History
The earliest magnets were the naturally occurring lodestone and magnetite. According to legend, a shepherd on the island of Crete first discovered lodestone when his iron-tipped crook was mysteriously attracted to a certain kind of rock. Archimedes, the Greek philosopher, used lodestone to draw nails out of the planking of enemy ships after their wreckage floated ashore.
The first known reference to lodestone dates back to 4000 BCE from a Chinese literary work called “Book of the Devil Valley Master.” By 1200 CE, Chinese sailors used lodestone as a compass. They tied a string around a lodestone and suspended it in the air. Once it stopped spinning, it orientated itself to a north-south direction.
Magnets as Health and Beauty Aids
There are stories that lodestone was thought to be a beauty aid. It kept the skin looking youthful. One report claims that Cleopatra kept lodestone under her pillow and slept on it for many years. About 2500 BCE, the Greeks also used magnets for therapeutic healing. Aristotle and Plato frequently made references to the healing powers of lodestone. Since 2000 BCE, the Chinese have used magnets in conjunction with reflexology and acupuncture, and they still use magnets today for some complaints. Warm lodestones placed on the patient’s back are supposed to align the spirit. Today medical science uses magnetism in magnetoencephalography (MEG) to measure brain activity.
More Magnetic Facts
All magnets that we use are bipoles, i.e. they have two poles, a north and a south pole. But researchers at the Large Hadron Collider (particle accelerator) at the CERN hope to find the elusive magnetic monopole. This is a theoretical magnet with either a north pole or a south pole, but not both.
Magnets are the basis for all electric motors and generators. Every electric motor depends upon magnets with electrical coils surrounding the magnet (solenoid). Electromagnets operate in telegraphs, telephones, computers and cell phones.
The MAGLEV (magnetically levitated train) is a single rail system where the train levitates above the track. This eliminates almost all friction wear on the train and the track. The trains can move at very high speeds. In theory, the speed could almost be infinite except for the wind resistance on the train. As technology advances, we will find many more uses for magnets.