# Formula 3. Maxwell equation (integral form) Electric field Magnetic field

## Electric field

`$$ \class{blue}{\boldsymbol{E}} $$`

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

`$$ \class{violet}{\boldsymbol{B}} $$`

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.