How to choose the magnet?

Before deciding which magnet to choose, what role should the magnet be required?

The main role: moving objects, fixed objects or lifting objects.

The shape of the magnets required: round, round, square, tile or special shape.

The required magnet size: length, width, height, diameter and tolerance and so on.

The required magnet suction, the desired price and quantity, and so on.

Compass is based on the nature of the invention of the magnet

1, guide north

2, to attract light objects

3, the solenoid can do electromagnetic relay

4, motor

5, generator

Pre-Qin era our ancestors have accumulated a lot of knowledge in this area, in the search for iron ore often encounter magnetite, that magnet (the main component is the iron tetroxide). These discoveries were recorded long ago. The first of several articles in The Pipe records these findings: "There are magnetites in the mountains and gold bronze under them."

Other ancient books such as "Shan Hai Jing" also have similar records. The iron absorption characteristics of the magnet were discovered very early, << Lu Spring and Autumn >> Nine volumes proficient articles are: << Ci Zhao iron, or lead also. >> At that time the people called 'magnetic' as 'Ci' They attract the magnet Iron as hermother's attraction to children. And that: "The stone is iron mother, but the stone is kind and not kind, kind of stone to attract his children, not kind of stone can not attract." Han people used to write the magnet as "charity" is The meaning of loving stone.

Since the magnet can attract iron, then whether it can attract other metals? Many attempts have been made by our ancestors to find that magnets not only can not attract metals such as gold, silver and copper, but also attract objects like brick and tile. During the Western Han Dynasty, people realized that magnets could only attract iron and could not attract other objects. When two magnets are brought together close to each other, sometimes attract each other, and sometimes mutually exclusive. Now people know that the magnet has two poles, one said N pole, one said S pole. Same sex very mutually exclusive, heterosexual very attract each other. The people at that time did not know this truth, but this phenomenon was still noticeable.

In the Western Han Dynasty, there was a large alchemist named Luan who used two properties of the magnet to make two pieces of chess. By adjusting the mutual position of the two chess pieces, sometimes the two chess pieces attract each other and sometimes exclude each other. Luan called it "fighting chess." He dedicated this novelty to Emperor Wudi and demonstrated on the spot. Emperor Wudi surprised, Longxin Yue, actually sealed Luan greatly "General Wuli." Luan big magnet with the nature of the novel made a deceptive Han Wudi.

The Earth is also a large magnet, with its two poles in close proximity to the geographic and the geographical North Pole. Therefore, the surface of the Earth's magnet, you can freely rotate, it will be the same sex repulsion magnets, heterosexual attract the nature of the North-South. The ancients did not understand this truth, but they are aware of such phenomena.