模拟带电粒子在电磁场中的运动。带电粒子在磁场中运动时会受到洛伦兹力的作用，且随着初始运动方向和磁场分布的不同，其运动轨迹会发生不同的变化。由洛伦兹力的推导公式可知，它垂直于粒子的运动速度，不对运动粒子作功，只改变其运动方向。(The motion of a charged particle in an electromagnetic field is simulated. When charged particles move in magnetic field, it will be affected by Lorenz force. With the initial motion direction and magnetic field distribution, the trajectories of them will change differently. The derivation formula of Lorenz force shows that it is perpendicular to the velocity of the particle and does not work on the moving particles, but only changes the direction of motion.)