当危险侧发生短路时，齐纳式安全栅中的电阻能起限能作用。

四开放作文
50
请根据下面提示，写一篇短文。词数不少于50.
In your English class, the teacher shows the picture below and asks the class to discuss it. Your classmates may have different understandings.
Look at the picture carefully and tell the class how YOU understand it.