# Questions tagged [poynting-vector]

The directional energy flux of an electromagnetic field. In conjunction with Poynting's theorem and the continuity equation, it used to express the conservation of electromagnetic energy, and to calculate the power flow in electric and magnetic fields.

145 questions
Filter by
Sorted by
Tagged with
24 views

### Electric field strength $d$km from a television transmitter of power $P$kW, assuming isotropic radiation

I think I need to use the Poynting vector to do this, as it is equal to the power per unit area flowing through a surface. At a distance $d$km from the transmitter, the surface will have a surface ...
24 views

39 views

### Energy carried by Electromagnetic Waves

The energy density carried by monochromatic planar Electromagnetic Waves is defined as: $u = \epsilon_0 E_0^2 cos^2(kz-\omega t + \delta)$ As this wave travels, it carries this energy along with it. ...
83 views

### Doubt in Poynting's theorem

In Griffiths's Electrodynamics, to explain Poynting's theorem, he writes: Suppose we have some charge and current configuration which at time t produces fields E and B. In the next instant dt the ...
42 views

### Poynting vector in metamaterials

Poynting vector in a material with magnetic permeability $\mu$ is defined as $\mathbf{S}=\frac{1}{\mu}(\mathbf{E} \times \mathbf{B})$ In certain media $\mu$ can be negative. In that case, $S$ will ...
27 views

### Is the Poynting vector always perpendicular to the plane a circuit lies in?

The Poynting vector is the cross product of electric and magnetic field (divided by $\mu_0$). Given an electric circuit that lies on the plane of a circuit board, the magnetic field is usually "...
59 views

72 views

330 views

### Intuition behind Poynting's theorem: relative sign between the electric and magnetic contributions to the energy

The standard derivation of Poynting's theorem for EEs uses sinusoidal complex time dependence $e^{\mathfrak{j} \omega t}$, that is $\mathbf{E}(t)=\Re [ \hat{\mathbf{E}}e^{\mathfrak{j} \omega t}]$ and ...