题目

       Real policemen , both in Britain and the United States, hardly recognize any similarity between their lives and what they see on TV—if they ever get home in time. There are similarities ,of course ,but the cops (policemen) don’t think much of them.        The first difference is that a policeman’s real life revolves round（以……为中心）the law. Most of his training is in criminal law. He has to know exactly what actions are crimes and what evidence can be used to prove them in court. He has to know nearly as much law as a professional lawyer, and what is more,18．小明同学认为根据R=$\frac{U}{I}$可知，导体的电阻和导体两端电压成正比，和通过导体的电流成反比，你认为小明的说法正确吗？为什么？