现行高中《物理》(必修 )第二册第四章第三节“自感”是本章的教学难点 ,而做好“通电自感”和“断电自感”两个演示实验 ,则是突破本节教学难点的关键 .课本设置“断电自感”演示实验 ,目的是使学生通过观察和了解电源断开时 ,通过小灯泡电流大小和方向变化情况 ,从而产生对自 The current high school “Physics” (required), Chapter IV, Chapter 3, “Self-induction” is the teaching difficulty of this chapter, and the demonstration experiments of “self-induction” and “power-off self-inductance” are breakthroughs. The key to teaching difficulties in this section is to set up a “power-off self-inductance” demonstration experiment. The purpose is to enable students to observe and understand when the power is off, through the small bulb current size and direction changes, resulting in self-