虚设法是一种应用“虚拟”和“假设”的思维方法。应用此方法求解某些物理习题 ,别开生面 ,可化难为易 ,化繁为简 ,化抽象为具体。举两例解析如下 :例 1　有 1 2只电阻值均为r的电阻组成一个立体框架 ,如图 1所示。求A、B两端的等效电阻Rab= ?解析　若直接运用串、并联电路的特 Virtual management is a way of thinking that applies “virtual” and “hypothetical” thinking. Use this method to solve some physics exercises, and make it difficult to make it easier to change. The two examples are as follows: Example 1 There are 12 resistors whose resistance values ​​are all r to form a three-dimensional frame, as shown in Figure 1. Find the equivalent resistance at both ends of A and B. Rab=?Analysis If you use the string and parallel circuit directly