Time variation of electric field $$\boldsymbol{E}$$ produces magnetic field $$\boldsymbol{B}$$ around the edge of surface $$A$$. This experimental result is called Ampere's law of electrodynamics and is mathematically summarized in the following Maxwell's equation:$\nabla \times \boldsymbol{B} ~=~ \frac{1}{c^2} \, \frac{\partial \boldsymbol{E}}{\partial t}$