在小学自然第6册第8课电磁铁实验教学中，铁钉尽管经火烧处理过，但反复实验后，余磁亦难消失。我教给学生一种简便易行的方法，效果非常好。即：将要消磁的铁钉与磁铁的南北极轻轻接触，即刻消磁，特别是利用蹄形磁铁的内侧南北极相互接触效果最好。电磁铁余磁消磁简法@王士龙 In the electromagnet experiment teaching of Elementary Book 6 of Book 6 of the Elementary School, although the nails were treated with fire, after the repeated experiments, the remaining magnetism was hard to disappear. I teach students a simple and easy way to do it. The effect is very good. That is, the nails to be demagnetized are brought into gentle contact with the north and south poles of the magnets, instantly degaussing, and in particular, the contact between the north and south poles of the inner side of the magnets is best. Electromagnet Magnetic Resonance Degaussing Method @ Wang Shilong