扇形磁场对带电离子汇聚的问题,既能考查学生应用数学知识处理物理问题的能力,又能考查学生的推理能力及分析综合能力,因此成为近几年的高考热点.笔者将以2008年重庆卷第25题为基础,从四个方面深入地研究扇形磁场对带电微粒(忽略重力)的方向聚焦规律.题目如图1所示为一种质谱仪的工作原理示 Fan magnetic field on the issue of charged ions, both to examine the students ability to deal with the use of mathematical knowledge of physical problems, but also to examine students’ reasoning ability and analysis of comprehensive ability, and thus become hot in recent years entrance examination. 25 questions as the basis, in-depth study from four aspects of the fan-shaped magnetic field on the charged particles (ignoring the gravity) the direction of focusing law. The title shown in Figure 1 for a mass spectrometer working principle