标题： 关于并联电路和导线上的洛伦兹力的实验 显示英文标题

标题： An Experiment About Parallel Circuit And The Lorentz Forces On Wires

摘要： 并联电路和载流导线上的洛伦兹力是入门物理课程中的重要概念。 这里我们描述一个演示这两个概念的实验。 我们将带有多个接地点的电路安装在扭秤上。 我们表明，接地点为供电电流创建了并联回路。 当回路的拓扑结构或形状改变时，电流在磁场中产生的洛伦兹力相应变化，这又导致扭秤的旋转位移发生变化。 这个实验简单，可以在教学实验室中轻松重现。 对学生来说有趣的是，最近有两个研究团队尝试检测微波驱动的非对称谐振腔（EmDrive 或 Cannae Drive）产生的推力，而本实验中可观测的现象为他们检测到的推力提供了一种替代解释。 显示英文摘要

摘要： Parallel circuit and the Lorentz forces on current carrying wires are important concepts in introductory physics courses. Here we describe an experiment that illustrates these two concepts. We mount a circuit with multiple grounding points onto a torsion balance. We show that the grounding points create parallel return paths for the supply current. When the topology or the shapes of the return paths are altered, the Lorentz forces exerted by the currents in the return paths within a magnetic field change accordingly, which in turn cause changes in the rotary displacement of the torsion balance. This experiment is simple and can be easily reproduced in a teaching laboratory. What makes it interesting to students is that recently two research teams have attempted to detect thrusts from microwave driven asymmetrical resonance cavities (EmDrive or Cannae Drive), and the phenomenon observable in this experiment provides an alternative explanation to the thrusts they detected.