Данная презентация рассказывает о видах и типах магнитов и о процессе магнетизм.
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«Magnets and Magnetism»
Magnets are divided into 2 categories: permanent and temporary.
A permanent magnet keeps its properties for a long time.
Permanent magnets can be natural and manufactured.
Magnetic rocks or loadstones are natural magnets.
These rocks retain their properties for several thousand years.
Many manufactured magnets are made of metal.
Metals with magnetic properties are iron, nickel, and cobalt.
An alloy called alnico is a very strong manufactured magnet.
It is made of iron, aluminum, nickel, and cobalt.
Ceramic magnet is a manufactured magnet made from special clay and iron oxide.
Ceramic magnets are very important to radio industry.
Permanent manufactured magnets have 3 shapes.
Bar magnet is straight and flat.
Bar magnets do not lose their properties easily.
A bar magnet has 2 poles(south and north), one at each end.
The needle of a compass is made of a small bar magnet.
A horseshoe magnet is shaped like a horseshoe.
This magnet is stronger than a bar magnet.
Its poles are close and are able to strengthen each other.
The horseshoe magnet loses its magnetism more quickly than the bar magnet.
If we place a bar of soft iron between the ends of a horseshoe magnet, it will help to preserve magnetism.
A bar of iron is called a keeper.
U-shaped magnet is shaped like U.
U-shaped magnet is not as strong as horse shaped magnet and loses its magnetism not as quickly as the horseshoe magnet.
Temporary magnet means that the material becomes magnetized for a short period of time by induction.
Temporary magnet is magnetized when it is pulled by another magnet.
This magnetism lasts for a few minutes.