蹭课，科普为主。顺便复习一些基础电路知识。
I am not a student of this class but want to listen to the lecture for popularization of science to myself.By the way reviewing some of the basic circuit knowledge.
给这篇文章写英译好辛苦……
It is hard to write English translation for this article.
肖大大图书镇楼！
Uncle Xiao’s book is superior!