一中空的横截面为正方形的长导体盒，与横截面垂直的方向上可认为是无限长。用求解横截面上电位的差分法和超松弛迭代计算拉普拉斯方程，-A hollow cross-section of a long conductor of square boxes, vertical cross-sectional direction can be considered infinitely long. Calculation of the Laplace equation by solving the cross section of the potential difference and over relaxation