十万个为什么·科学启蒙30篇（3）
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Why Can Magnets Attract Iron?
为什么磁铁能吸铁
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Magnets attract iron because iron atoms have unpaired electrons that create tiny magnetic fields.
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In unmagnetized iron, these atomic magnets point in random directions, canceling each other out.
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When a strong magnet comes near, it causes many of these tiny fields to line up temporarily.
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This alignment turns the iron into a temporary magnet with opposite polarity facing the original one.
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Opposite magnetic poles attract, so the iron jumps toward the magnet with noticeable force.
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Other metals like nickel and cobalt behave similarly, but aluminum or copper do not react this way.
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Heating or dropping a magnetized piece of iron scrambles the alignment and removes its magnetism.
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Permanent magnets stay magnetic because their atomic fields lock into place within a rigid crystal structure.
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Earth itself acts like a giant magnet, which is why compass needles always point north.
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This force works without contact because magnetic fields extend invisibly through space around the magnet.