热学中的临界问题,具有灵活性大,隐蔽性强的特点,对学生能力要求较高,笔者将一些典型的问题集中起来,供大家参考.类型一、升温溢出水银例1　粗细均匀的玻璃管的长度L=100cm,下端封闭,上端开口,竖直放置如图1甲所示,在开口端有一段长度为h=25cm的水银柱把管内一段空气封住,水银 The critical issue in thermal science has the characteristics of great flexibility and strong concealment. It has a higher requirement for students’ ability. The author will focus on some typical problems for your reference. Type I. Overheated overflow mercury case 1 Thick and uniform glass tube The length L=100cm, the lower end is closed, the upper end is open, and is vertically placed as shown in FIG. 1A. A mercury column with a length of h=25 cm is sealed at the open end to seal the air in the tube.