Formula: 3. Maxwell equation (integral form) Electric field (E field) Magnetic flux density (B-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 $$ \frac{\mathrm{V}}{\mathrm{m}} = \frac{\mathrm{N}}{\mathrm{C}} = \frac{\mathrm{kg} \, \mathrm{m}}{\mathrm{A} \, \mathrm{s}^3} $$
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 $$ \mathrm{T} = \frac{\mathrm{kg}}{\mathrm{A} \, \mathrm{s}^2} $$
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.