# Formula 2. Maxwell equation (differential form) Magnetic field

## Magnetic field

`\( \class{violet}{\boldsymbol{B}} \)`Unit

`\( \text{T} \)`

Magnetic flux density determines the magnitude and direction of the magnetic force on a moving electric charge.

## Divergence field

`\( \nabla \cdot \class{violet}{\boldsymbol{B}} \)`Unit

`\( \frac{\text T}{ \text m} \)`

Scalar divergence field is the scalar product between the nabla operator \(\nabla\) and the magnetic field \( \boldsymbol{B} \):

`\[ \nabla \cdot \class{violet}{\boldsymbol{B}} ~=~ \frac{\partial \class{violet}{B_{\text x}}}{\partial x} + \frac{\partial \class{violet}{B_{\text y}}}{\partial y} + \frac{\partial \class{violet}{B_{\text z}}}{\partial z} \]`The divergence field is no longer a vector field but a scalar function. The divergence field \( \nabla \cdot \class{violet}{\boldsymbol{B}(x,y,z)} \) at the location \((x,y,z)\) is always zero. This means that there are no magnetic charges.