初中课本中有一个绝缘体变导体的演示实验，把玻璃加热到红炽热状态，它就变成导体了。学生对这个实验很感兴趣，但是利用课本上的装置很难达到预期的效果。主要问题有：①要用酒精灯加热灯芯很久才使电路导通，这样浪费了宝贵的上课时间；②加热时，教师一个人很难操纵整个实 In the junior high school textbook, there was an experiment demonstrating that the insulator changed the conductor and heated the glass to the red-hot state, and it became a conductor. Students are very interested in this experiment, but it is difficult to achieve the desired effect using textbooks. The main problems are: 1 The use of alcohol lamps to heat the wick for a long time to make the circuit turn on, which wastes valuable class time; 2 When the heating, the teacher is difficult to manipulate the whole