第六届全国中学生物理竞赛第九道题,要求计算原来不带电的导体小球接受有补偿来源的导体大球的反复充电后的极限带电量。此题的实质,是求两个不同的电容器,经过反复多次并联后的电量分配,因此牵涉到孤立导体的电容问题,而这一课题是超出中学阶段学生知识水平的。不过,作为检查学生灵活运用知识的能力, The ninth title of the Sixth National Physics Competition for Middle School Students asks to calculate the limit charge quantity after repeated charging of a conductor ball with a source of compensation from a ball that has not been charged. The essence of this question is to find two different capacitors, and after repeated multiple times of parallel power distribution, it involves the problem of the capacitance of isolated conductors, which is beyond the knowledge level of students in secondary school. However, as an ability to inspect students’ knowledge,