Should be clear before decided to choose which kind of magnet need magnets play what role?
Major role: moving object, fixed object or lift.
The shape of magnet required: wafer form, circular, square shape, tile shape or special shape.
Required for the size of the magnet: long, wide, high, diameter and tolerance, and so on.
Suction of the magnet, the expected price and quantity and so on.
Invented the compass is according to the properties of magnets 1, 2, refers to the north and the south, small objects attract light 3, electromagnet electromagnetic relay can do 4, 5 of the motor, generator, the pre-qin period our ancestors have accumulated a lot of knowledge in this field, in exploring often encounter magnetite iron ore mine is a magnet (
Main ingredients are ferroferric oxide)
These findings were recorded very early.
'Pipe' in the number of the earliest recorded these findings: 'the mountains have a magnet, copper with gold.
In the other ancient books such as 'shanhaijing have similar records.
Iron absorption properties of a magnet was found early, the 'spring and autumn annals' nine volumes master piece is: 'goodness for iron, or quote also.
'When they called' magnetic '' kindness' they put a magnet attracts iron as a loving mother for their children.
And said: 'the stone is the mother of iron, but there are stone and not kind, loving stone attracted to his children, not goodness stones cannot be attracted.
'Han' CiShi ', people used to write the magnet do means love stone.
Since a magnet attracts iron, so whether can attract other metal?
Our ancestors made many attempts to find a magnet not only fail to attract such metals as gold, silver, copper, and can't attract items such as brick.
The western han dynasty when people have realized a magnet tend only to attract the iron, and can't attract other items.
When put two magnets together close to each other, attract each other, sometimes sometimes mutually exclusive.
Now there are two people all know magnet, a N pole, said a S pole.
Gay mutually exclusive, opposite pole attract each other.
When people do not know this truth, but for this phenomenon is able to detect.
In the western han dynasty, there was a named Luan big alchemist, he took advantage of the properties of magnets made two pieces of things, by adjusting the two pieces of polarity, sometimes two pieces attract each other, sometimes mutually exclusive.
Luan big described it as 'dou chess'.
He dedicated the curiosity to the emperor, and demonstration on the spot.
The emperor was amazed, honour-so delighted, unexpectedly sealing LuanDaWei 'five generals'.
Luan by using the properties of magnets, made a curiosity deceive the emperor.
The earth is a big magnet, its two very near the geographic South Pole and the geographic North Pole.
So the magnets on the surface of the earth, can free rotation, will be for the same magnets, opposites attract indicating the nature of the north and south.
The ancients is not enough to understand this truth, but they know this kind of phenomenon.
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