画示意图是中学物理教学中一项基本技能的训练,不仅有物体的受力图、电路图、光路图等,而是在其他许多方面也常要用图来表示。譬如,常常需要用图来表示一些实验装置或操作机构;或者用图来简述某个物理现象、解剖某个物理过程;特别是常常可以借助示意图来帮助审题和解题。经常会遇到这样的情况:有些学生指着书上的习题说“不会做”,但是,一旦让他们把题目仔细看一遍,引导他们画一张图,把题中条件图示化后,学生往往会顿然领悟,笑逐颜开了。譬如,在讲到玻一马定律时,我们分析了这样一个问题:[题1]氧气瓶的容积是32升,充气后压强达130千克/厘米~2,一般规定使用到压强降到10干克/厘米~2时,就要重新充气。某厂吹玻璃每天要用400升氧气(在一个大气压下),问:一瓶氧气能用 Schematic drawing is a basic skill training in physics teaching in middle school. There are not only force diagrams, circuit diagrams, and light path diagrams of objects, but they are often expressed in diagrams in many other aspects. For example, it is often necessary to use diagrams to represent some experimental devices or operating mechanisms; or to use diagrams to describe a certain physical phenomenon and to dissect a physical process; in particular, it is often possible to help examine questions and solve problems with the help of diagrams. This is often the case: Some students point to the book’s exercises and say “No,” but once they have been asked to look carefully at the subject, they are guided to draw a picture and the conditions in the question are plotted. Students tend to suddenly realize and smile. For example, when we talked about the law of glass and horses, we analyzed such a problem: [Q1] The volume of the oxygen cylinder is 32 liters, and the pressure after inflation is 130 kg/cm2. Generally, the pressure is reduced to 10 dry. When g/cm~2, it is necessary to re-inflate. A glass factory uses 400 liters of oxygen per day (at one atmosphere pressure). Q: A bottle of oxygen can be used