在沪科版《物理》选修3-1第二章“电场与示波器”的教学中,几种常见的电场线的分布是学习的重点,能够正确得出电场线的分布情况,则能有效地解决粒子的运动问题。在教学中,尤其是等量同种电荷中垂线上,中点电场强度为0,在无穷远处也为0,在中垂线由中点向两侧电场强度先增大后减小,但是最大值究竟在什么位置;这一问题对于粒子运动的加速度的判断至关重要,这也是学生和教师困惑的地方。本文巧用数学求导的思想,有效地解决了这一问题。 In Shanghai Science and Technology version of “Physics” elective 3-1 Chapter 2 “electric field and oscilloscope ” teaching, the distribution of several common electric field lines is the focus of learning, can correctly draw the distribution of electric field lines, then Effectively solve the particle movement problem. In teaching, especially in the same amount of the same type of charge in the vertical, the midpoint electric field strength is 0, also at infinity 0, in the vertical from the midpoint to both sides of the electric field strength first increased and then decreased, But where exactly the maximum is; this question is crucial for judging the acceleration of particle motion. This is where students and teachers are confused. This article clever use of mathematical thinking, effectively solve this problem.