It shows that electric field lines start with positive charge or infinity and end with negative charge or infinity. They are uninterrupted and disjoint, and do not form a loop where there is no charge.

Gauss theorem tells us that electric field lines have a source or an end, which are uninterrupted and disjoint. If the integral of the electric field to a plane around a place is not equal to zero, then this integral (electric field flux) is equal to the total charge in the plane divided by the vacuum electrostatic constant, which is Gauss theorem. According to the sign, the direction of the electric field line and the sign of the charge in the plane can be judged. Similarly, if the electric field lines are discontinuous and intersect, the electric field flux is not zero where there is no charge, but Gauss theorem tells us that this is impossible.

The loop theorem tells us that electric field lines will not form loops (loops). In electrostatic field, the integral of electric field to any loop is equal to zero, which is the loop theorem. If it is not equal to zero, then this electric field is no longer an electrostatic field.