作者:admin 来源: 2015-7-8 13:30
[煎蛋小学堂]如何让磁铁消磁? 节目简介: 你是不是对日常生活中一些稀松平常的现象产生过好奇心? 到底为什么会是酱紫的呢? 科普类视频节目《煎蛋小学堂》几分钟为让你茅塞顿开,双语文本+视频+MP3更是不容错过的英语口语、口译好素材呢~~ 还在等什么,一起来一场对未知世界的奇妙探索之旅吧~~ 参考双语文本: This is a neodymium magnet-it's pretty darn strong.And now,after heating it in a's no longer magnetic.Well,to build a magnet,all you need to do is find a bunch of magnetic atoms .

That's easy-they're the ones with half-filled electron shells in the middle of any of the major blocks of the periodic table, and then make a compound where the magnetic fields of the atoms align in the same direction this is Ferromagnetism, named after Iron,which is pretty darn magnetic.

However,it's not always so easy.Sometimes the atoms actually want to align their magnetic fields in alternating directions.This is called "anti-ferromagnetism,"and it means the bulk material won't have a magnetic field at all.Or,sometimes the tendency of the atomic magnets to align (or anti-align)is just too weak to overcome their intrinsic jiggling.

That is,their temperature!In which case,even though all the individual atoms in the material are magnetic,the material as a whole isn't.However,in a strong external magnetic field,the atoms do tend to align with each other in the direction parallel to the field.This is called "para-magnetism,"and liquid oxygen is a great example:it's attracted by a magnet,though it doesn't stay magnetized afterwards.
也就是温度!此时即使材料内部所有原子都具有磁性,整块材料却没有 但是 在外部强磁场内,原子会沿平行于外部场的方向相互对齐,这就是顺磁性,液氧就是个好例子,它会被磁铁吸引,但之后并不会保持磁性。

But let's get back to the question-how do you destroy a magnet?Well,a material can only be ferromagnetic it its temperature is low enough:above a certain point,the nicely ordered atomic magnetic fields"melt"into disorder,just as ice crystals melt into water when heated past zero celsius. So to destroy a manget,you just need to heat it up past its "magnetic melting point",called the "Curie Temperature"it probably won't look like much is happening,but once the atoms are jiggling around enough,their magnetic fields will no longer all point in the same direction.

Magnet destroyed!And just as different elements melt from solid to liquid at different temperatures,They also melt from being ferromagnetic to paramagnetic at different temperatures,which you can explore in this sweet interactive periodic table.Which also plays all of the Periodic Table of Videos.
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