变化的磁场产生感生电场,此电场分布于整个空间,导体回路处于感生电场中产生感生电动势.本文针对一道电磁感应习题,指出中学阶段常见解答中的科学性错误,并定量计算了区域为正方形的变化磁场所激发的感生电场,从而正确求出导体回路中的两点在感生电场中的电势差. The changing magnetic field produces an induced electric field, which is distributed in the whole space, and the conductor loop is induced in the induced electric field to generate induced electromotive force.In this paper, an electromagnetic induction problem is pointed out, and the scientific errors in the common solutions of the middle school stage are pointed out. For the square magnetic field induced changes induced electric field, so as to correctly find the two points in the conductor loop in the induced electric field potential difference.