Because the Gaussian surface we chose was a sphere concentric with the point charge, the  electric field and the area vector were always in the same direction giving an angle of zero degrees  in the dot product.

因为我们选择的高斯表面是与点电荷同心的球体，所以电场和面积矢量始终朝同一方向， 从而在点积中产生零度角。