叶圣陶教学思想对当前教改的借鉴意义

The Function of the Neutral Wire and its Protection When Broken

叶老主张“‘教’都是为了达到用不着‘教’”,这就是他的“学导”思想。叶老对教师的教、学生的学进行了多方面的表述 ,他的教学思想可以概括为 :变教为学 ;变授为导 ;变知为力 ;变形为效。

In the Threephase and Fourwire circuit system,the neutral wire is very important.When neutral wire is broken,in the case of unbalanced load,the voltage of the Threephase load terminal will is not normal.So the load can not regularly work and even the device will be damaged when it is serious.So it is main discussed in this article about the function of the neutral wire and the protection when it breaks