Magnets, deep in our childhood memories, it is a wonderful thing. The class was to play in the classroom magnet war, two soldiers each holding a magnet magnetic force on both sides of the center line while away, and wait for the next referee gave the order to let go of both sides at the same time, cross-border transport operators magnet will be taken away, play is also not music almost. We can still see Jerry Mouse Tom Cat is using a magnet get the whole wreck on the cartoon "Tom and Jerry."
Growing up our lives without it, take the maglev train, the hospital's MRI, with stereo speakers, first to developed countries on military guns ...... magnets There are so many fantastic features, today together with you to understand a bit.
Usually we know that is a magnet repel each other and attract each object has. Magnets are made of iron, nickel, cobalt, whose magnetic moment itself, an internal structure arranged in the same direction, one end of the north pole (N pole) end south (S pole).
So there are many objects in nature Why not magnetic? Iron, nickel, cobalt magnetic substance vary uniformly arranged inside the electronic spontaneously its direction, the magnetic reinforcing constitute a magnet.
The magnet iron absorption process appeal to iron, and the iron magnet "stick" together, we say that the magnetic magnet, which magnet can attract iron is not absorbing aluminum or copper object, the internal structure of different metals are different. Tesla magnetic induction units, referred to as Patent (T).
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Permanent magnet and the magnet is divided into a non-permanent magnet, the permanent magnet is able to maintain long-term non-volatile magnetic magnetic and natural products, such as magnetite. Non-permanent magnets required under certain conditions to appear magnetism, such as electromagnets.
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Development of magnet:
The manufacturing process of the permanent magnet
casting
Need to make the first magnet form a sand mold, it may be cast magnet, the material comprises copper, cobalt, sulfur, nickel, iron, aluminum, and titanium. Electromagnetic metal into the furnace, heated to above 1600 deg.] C, all the metals are melted into a liquid.
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The solution was poured into a sand mold, the sand mold will burn, because the flammable gas is hardened sand.
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Forced open casting with a hammer mill, to allow air into the casting mill coolant, so that the gas burn. Branched off from the metal block sand, or ordinary iron metal after casting, it does not have any magnetic force.
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The metal member tied brass, into a larger tube, the copper tube in the middle, surrounded by closely filled with silica sand, concrete with sealed ends is exposed ends brass.
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放入火炉内加热700℃后取出，用夹钳固定住铜管两端，通低压高电荷电流，然后取出金属件，这步已让金属件轻微磁化，正确建立了磁场方向。
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通过充磁机器让磁铁生效， 机器会通过电流把磁性传到金属上让其产生磁性。通交流电后首先对电容充有高压电压（储能），然后通过一个电阻非常小的线圈放电。放电时电流峰值很高，可达数万安培。电磁产生的强大的磁场可使金属永久磁化。
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还有人会有疑问磁铁会有辐射吗？其实地球就是一个大磁石，人类无时无刻不在受磁场的影响，人体都有不同程度的微磁场，较弱且稳定的磁场对人体是有好处的。磁铁只产生恒定磁场，不叫辐射，只能叫磁场。
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钕磁铁也叫钕铁硼磁铁是目前磁性最强的磁铁，它能吸附自身体重640倍的重量，被称为最强力磁铁。其硬度高、性能稳定广泛用于电子产品上，如硬盘，手机，耳机等。
注意一点，钕磁铁采用烧结成型，而普通磁铁是浇铸工艺，由于材料中含有钕和铁所以表面容易生锈，需要做一些保护性电镀处理，这也算是它的一个缺点吧。
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我们在使用磁铁过程中会发现磁力越强就更易碎，这是由它的物理特性造成的。磁铁在生产过程中采用粉末烧结而成的，烧结时间长，其内部都是一块死的，缺乏灵活性。
磁铁在强大的磁场下相吸相斥也会给磁铁本身很大的反作用力，当碰到其它坚硬物体就容易碎。磁铁破碎后每块小磁铁仍然有S极N极，这是因为任何磁体的磁极总是成对出现，破碎并不能把它的北极同其南极分开，每块磁铁不管有多小都有自己的两极。
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跟大家聊一下军事上的高科技武器，电磁炮。它是在炮管内安装线圈，通电后在炮管内产生强大电磁场力，使弹丸加速运动并发射出去。速度可达11千米/秒，这个速度可以使任何目标瞬间灰飞烟灭，它的炮弹就是普通的金属弹丸，造价非常便宜。
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