Formula 3. Maxwell equation (integral form) Electric field Magnetic field
$$\oint_{L} \class{blue}{\boldsymbol{E}} ~\cdot~ \text{d}\boldsymbol{l} ~=~ -\int_{A} \frac{\partial \class{violet}{\boldsymbol{B}} }{\partial t} ~\cdot~ \text{d}\boldsymbol{a}$$
Electric field
\( \class{blue}{\boldsymbol{E}} \) Unit \( \frac{\text V}{\text m} \) Electric field indicates how large and in what direction the electric force on a charge would be if that charge were placed at location \((x,y,z)\).
In the third Maxwell equation in integral form, on the left-hand side is the line integral of the electric field, which corresponds to the voltage along the line \(L\).
Magnetic field
\( \class{violet}{\boldsymbol{B}} \) Unit \( \text{T} \) Magnetic flux density determines the force on a moving electric charge.
On the right-hand side of the third Maxwell's equation is the negative temporal change of the magnetic flux. Minus sign accounts for the Lenz rule. The third Maxwell equation means that a magnetic field changing in time causes an electric voltage and vice versa.