十万个为什么·科学启蒙30篇（3）

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为什么磁铁能吸铁

Magnets attract iron because iron atoms have unpaired electrons that create tiny magnetic fields.
In unmagnetized iron, these atomic magnets point in random directions, canceling each other out.
When a strong magnet comes near, it causes many of these tiny fields to line up temporarily.
This alignment turns the iron into a temporary magnet with opposite polarity facing the original one.
Opposite magnetic poles attract, so the iron jumps toward the magnet with noticeable force.
Other metals like nickel and cobalt behave similarly, but aluminum or copper do not react this way.
Heating or dropping a magnetized piece of iron scrambles the alignment and removes its magnetism.
Permanent magnets stay magnetic because their atomic fields lock into place within a rigid crystal structure.
Earth itself acts like a giant magnet, which is why compass needles always point north.
This force works without contact because magnetic fields extend invisibly through space around the magnet.