一、问题的提出高二物理期末考试中,笔者出了下面这样一道题目:传感器是把非电学量的变化转变成电学量变化的一种元件,在自动控制中有着相当广泛的应用。如图(1)是一种测定液面高度的电容式传感器的示意图,金属芯与导电液体形成一个电容器,从指示器显示的电容C大小变化就能反映液面的升降情况,两 First, the question raised in the second year of the Physics Physics final examination, the author has put out such a topic as follows: The sensor is a kind of element which changes the non-electric quantity change into the electric quantity change, has very extensive application in the automatic control. Figure (1) is a schematic diagram of a capacitive sensor for measuring the liquid level. The metal core and the conductive liquid form a capacitor. The change of the capacitance C shown by the indicator can reflect the rise and fall of the liquid level.