Alexander Fufaev
My name is Alexander FufaeV and here I will explain the following topic:

Poynting Vector: Energy Flow of an Electromagnetic Field

Formula

Formula: Poynting Vector
Poynting Vector
What do the formula symbols mean?

Power density

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: $$ \mu_0 ~=~ 1.256 \, 637 \, 062 \, 12 ~\cdot~ 10^{-6} \, \frac{\mathrm{Vs}}{\mathrm{Am}} $$
Explanation

Video

Poynting vector \( \boldsymbol S \) describes the energy that passes through a cross-sectional area per unit time. The Poynting vector is therefore a power density. The unit of the Poynting vector is watts per square meter.

Formula anchor
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Poynting Vector