# Formula 2. Maxwell equation (integral form)

## Magnetic field

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

`$$ $$`

Magnetic flux density determines the force on a moving electric charge.

The second Maxwell equation states that the magnetic flux (i.e., the integral of \(\boldsymbol{B}\) over a closed surface) is always zero. In other words, there are no magnetic monopoles that would generate the flux through a surface.

## Surface

`$$ A $$`Unit

`$$ $$`

The surface over which the magnetic field \( \boldsymbol{B} \) is integrated. This can be, for example, a spherical surface or a cylindrical surface.

Here \( \text{d}\boldsymbol{a} \) is a small surface element. The direction of \(\text{d}\boldsymbol{a}\) is perpendicular to the respective surface element by definition.