重力不计的带电粒子垂直于磁场方向射入有边界的磁场区域后,一定会从磁场区域边界的另一点射出,求解这个磁场区域的最小面积时,往往是先将带电粒子在磁场中运动的这部分圆轨迹先做出来,再将射入磁场的点与射出磁场的点用直线相连,即轨迹圆的一条弦,最后由这条弦来确定最小磁场区域的 When the charged particles of gravity are perpendicular to the direction of magnetic field and enter the bounding magnetic field region, they must be emitted from another point on the boundary of the magnetic region. When solving the minimum area of ​​this magnetic region, it is often the first that the charged particles move in the magnetic field Part of the circular trajectory to do it, and then point into the magnetic field and the point of the magnetic field is connected with a straight line, that is, a track of the circle, and finally by the string to determine the minimum magnetic field