Magnetism
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In the field of physics, magnetism is a force by which objects attract or push away other materials.
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[change] Magnets
Magnetism can be seen in special objects called magnets. When magnets are placed near objects that are magnetic, the magnet will attract the object and pull it to the magnet. Magnets can also push away other objects. The most common objects that are attracted to magnets contain iron or steel. Most other metals, including aluminum, are not attracted to magnets.
[change] Magnetic fields
Magnets have an area, or distance, around them called a magnetic field. Objects inside the magnetic field can be attracted to the magnet. Objects outside the magnetic field will not be attracted to the magnet. This is why a magnet must be placed close to an object to attract it.
[change] Structure
The ends of a magnet are called magnetic poles. This is where the force of a magnet is the strongest. All magnets have a north pole and a south pole. If a magnet is allowed to spin, then the north pole of a magnet will always point to the Earth's north pole. The south pole of a magnet will point to Earth's south pole. You can try this yourself by tying a string to a bar magnet and then holding the string so that the magnet can turn.
Like poles of two magnets always push away, or repel, each other. Different poles attract each other. For example, if the south pole of one magnet is put near the south pole of another magnet, the magnets will push away from each other. This will also happen with two north poles. But if a north pole is put near a south pole, the magnets will move toward each other until they stick together.
[change] Uses
Magnets have many uses. One use was discovered long ago when explorers found out a magnet could be used as a compass to show the locations of the poles on the Earth.
[change] Electromagnets
Electromagnets are another kind of magnet that only work when electricity is running through them. Often, these magnets function using a coil of wire that creates a magnetic field when there is a current through it. In addition to this coil of wire, a large piece of metal, generally iron, is placed inside the coil to greatly strengthen the magnetic field produced. Though most large electromagnets employ many solenoids to lift heavy objects, smaller solenoids are used in everyday electronics, for example to change a voltage in a transformer.
[change] Uses
Electromagnets are used to make computers, televisions and radios work, for example.
[change] Effects
The effect of magnetism on global warming has not yet been researched. It is believed that severe climate change affects the earth's magnetism. However, it is proved to be untrue. The earth does switch its own magnetic poles about every million years (plus or minus 200,000 years). Before a flip of magnetic field, the earth's magnetic field weakens and sways around, like a top would before it falls. The earth has already undergone hundreds of "flip flops" during its lifetime. Scientists know this as a result of studies of the sea floor, particularly around the mid-Atlantic ridge. The lava slowly seeps out of this crevasse (gap) and cools with its iron molecules aligned in the direction of the Earth's magnetic field. We can measure this recorded magnetic field today to look back at the many flips in the past.
[change] Electromagnetic waves
Electromagnetic waves are used in radio for transmitting signals from the satellite to the radio.
