vortex of vector field

The lines of eddy electric field that is excited by approach to steady current,have two cases:①each of the line is closed;②two ends of the line extend to infinity.

似稳电流产生的涡旋电场的场线在空间的分布呈两种典型状况:①场线是闭合曲线;②场线是两端伸向无穷远的曲线。