要测定条形磁体的磁感线走向,可以在条形磁体中间挖一个洞,再放入一个小磁针,观察磁针北极指向.但是条形磁体上面挖洞不容易,并且一般学校条形磁体较小,不能再挖洞放入磁针.有没有不在磁体上挖洞,又能测其内部磁感线走向的方法呢?笔者为此做了两个实验. To determine the direction of magnetic lines of influence of bar magnets, a hole may be dug in the middle of the bar magnet, and then a small magnetic needle may be placed to observe the north direction of the magnetic needle. However, it is not easy to dig holes above the bar magnets, and the bar magnets in general schools are relatively Small, can not dig holes into the magnetic needle. There is no way to dig the hole in the magnet, but can measure the direction of its internal magnetic induction line? The author made two experiments for this purpose.