E&M energy density near a radiating hi Q half-wave antenna.

[Spinnor]

A high Q antenna basically means the antenna stores a large amount of energy in the near fields compared with the electromagnetic energy radiated per cycle?

When the alternating current momentarily stops in our half-wave antenna charge density is maximum at the ends of the antenna, and the electrostatic energy density is maximum near the poles of the antenna?

A quarter cycle latter the current density peaks and is maximum at the mid point of the antenna, and therefore magnetic energy density is momentarily maximum near the center of the antenna?

Is there then a cyclic flow of energy from the polar regions to the mid-section of our antenna and then back again (ignore the outward radial flow of energy which for a high Q antenna will be minor compared with near field energy density)?

Are there any good Apps that show this cyclic flow of energy? I did find a great set of physics apps, one in particular that shows the energy density near the antenna but the results don't seem to fit my naive guess.

Screen shots below show the energy density near the antenna. The app is at,

http://www.falstad.com/emwave1/

which is from a large list of physics apps,

http://www.falstad.com/mathphysics.html

Thanks for any help!

Edit, the following crude picture of energy flow is more in line with my thoughts,

http://www.google.com/imgres?start=...0CCkQhBwwDDhk&iact=rc&dur=1778&page=6&ndsp=22

 

[eljose79]

Thank you for your post. Your understanding of a high Q antenna is generally correct. A high Q antenna is one that has a high quality factor, meaning it is able to store a large amount of energy in its near fields compared to the energy that is radiated per cycle. This is due to the antenna's ability to maintain a strong resonance at a specific frequency.

In terms of the alternating current flow, you are correct that there is a cyclic flow of energy from the polar regions to the mid-section of the antenna and back again. This is due to the antenna's ability to oscillate at its resonant frequency, causing the electric and magnetic fields to alternate between the ends and center of the antenna.

As for apps that can show this cyclic flow of energy, I would recommend looking for simulations or animations of antennas in action. There are many resources available online that can demonstrate the behavior of antennas, such as the app you mentioned or other physics simulation programs. Additionally, you may also find helpful resources through scientific journals or textbooks on antennas and electromagnetics.

I hope this helps clarify your understanding of high Q antennas. Keep exploring and learning about this fascinating topic!