带电粒子垂直射入有边界的匀强磁场,其运动轨迹常是一段圆弧,这时对粒子运动轨迹的几何分析往往成为解题的关键,而能否确定粒子轨迹圆的圆心,又是轨迹几何分析的必要前提.下面就轨迹圆心的确定分几种情况来讨论. The charged particles are injected perpendicularly into the uniform magnetic field with boundary. The motion trajectory is often a circular arc. At this time, the geometric analysis of the particle motion trajectory often becomes the key to solving the problem. The center of the particle trajectory circle can be determined as a trajectory. The necessary preconditions for geometric analysis. The following discussion is based on the determination of the trajectory center.