A time-varying electric field $$\boldsymbol{E}(t)$$ and/or a constant electric current $$I$$ through a surface $$A$$ create a time-dependent magnetic field $$\boldsymbol{B}(t)$$ which forms a vortex along the edge of the surface $$A$$. This can be summarized in the following 4th Maxwell equation in integral form:$\oint_{L} \boldsymbol{B} ~\cdot~ \text{d}\boldsymbol{l} ~=~ \mu_0 \, I + \int_{A} \frac{\partial \boldsymbol{E}}{\partial t} ~\cdot~ \text{d}\boldsymbol{a}$