Even if we used grid electricity to cut off the permanent magnet's field by shielding it with something, wouldn't we save a lot more energy than using an electromagnet?
即使我们使用电网电力切断屏蔽的东西它的永久磁铁的领域，我们不会节省很多比用电磁铁的能量？
Even if we used grid electricity to cut off the permanent magnet's field by shielding it with something, wouldn't we save a lot more energy than using an electromagnet?
即使我们使用电网电力切断屏蔽的东西它的永久磁铁的领域，我们不会节省很多比用电磁铁的能量？
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