Topic: Electromagnetics
The electric field intensity E and magnetic field intensity H are coupled and propagating in free space in x and y direction respectively, the Poynting vector is given by
- A. EH
- B. EHy
- C. EHxy
- D. none of the above
Answer: D. none of the above
Explanation: The Poynting Vector represents the directional energy flux density of an electromagnetic field, given by $\vec{P} = \vec{E} \times \vec{H} \text{ Watt/m}^{2}$.
If $\vec{E}$ is in the x-direction ($E_{x}\hat{a}_{x}$) and $\vec{H}$ is in the y-direction ($E_{y}\hat{a}_{y}$), then $\vec{P} = E_{x}\hat{a}_{x} \times E_{y}\hat{a}_{y} = E H \hat{a}_{z}$.
Since the result is in the z-direction, none of the provided options (a, b, c) accurately describe the vector $EH\hat{a}_z$, making (d) the correct choice.