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.

Relationship between the induced electric field and the current that sets up the field;

Through the analysis of Maxwell s equations it is concluted that under the quasi-stationary conditions the induced electric field can be calculated in terms of the solution of the static magnetic field.

The vortex electric field produced by seemingly stable magnetic field;

By analyzing Maxwell equation with contrast, the teacher introduces students the concept of vortex electric field & displacement, then the integral of Maxwell equation shows the close relationship of magnetic field and electric field, and becomes the basic theory of electro magnetic field.

The eddy electric field will react to the alternating magnetic field.