# Formula Poynting Vector Power density    Magnetic field    Electric field

## Power density

Unit
Poynting vector describes the energy passing through a cross-sectional area per unit time. The Poynting vector is thus a power density.

The cross-sectional area is spanned by $$\boldsymbol{E}$$ and $$\boldsymbol{B}$$. The Poynting vector is orthogonal to $$\boldsymbol{E}$$ and $$\boldsymbol{B}$$.

## Magnetic field

Unit
Magnetic flux density determines the strength of the magnetic field and thus the magnitude of the Poynting vector.

## Electric field

Unit
The E-field vector indicates the strength of the electric field. The magnitude of the E-field determines the magnitude of the Poynting vector.

## Vacuum permeability

Unit
The vacuum permeability is a physical constant and has the following experimentally determined value:$$\mu_0 ~=~ 1.256 \, 637 \, 062 \, 12 ~\cdot~ 10^{-6} \, \frac{\mathrm{Vs}}{\mathrm{Am}}$$