The condition for application of electrostatic theory

[hectoryx]

In the vicinity of antenna, electric field strength have terms that vary as 1/r, 1/(r^2), and 1/(r^3). The terms varying as 1/(r^3) are called the quasi-electrostatic field which can be analyzed with the theory of electrostatic field. The condition is that the size of interested area is less than wavelength/2pi.

My question is that for the frequency of 50MHz, the size must be less than 0.95m according to the theory above. Now there is a big sphere (good dielectric) placed near the antenna. The distance between the bit sphere and the antenna is 0.1m. More important, the diameter of the big sphere is 2m.

Then, if we want to discuss the electric filed distribution, could we use the theory of electrostatic field? If not, what theory should we use? And besides, if we want to use electrostatic filed theory, what is the upper limit of frequency in this condition?

Thanks in advance.

Regards.

Hector

 

[Vailanor]

.No, you cannot use the theory of electrostatic field to analyze the electric field distribution in this case. The size of the interested area (2m) exceeds the wavelength/2pi (0.95m) at the frequency of 50MHz. Thus, the conditions for using the theory of electrostatic field are not satisfied. In this case, you should use the theory of electromagnetic waves. This theory can be used to analyze the electric field distribution in the vicinity of the antenna even when the size of the interested area is larger than the wavelength/2pi. In fact, the upper limit of frequency using this theory is not determinate; it depends on the application.

 

[astrokreng]

The conditions for the application of electrostatic theory in this scenario are that the size of the area of interest must be less than the wavelength/2pi and the presence of a good dielectric material, such as the big sphere in this case, must not significantly affect the electric field distribution.

In this situation, the distance between the big sphere and the antenna is 0.1m, which is much smaller than the wavelength/2pi for a frequency of 50MHz, meaning that the condition for applying electrostatic theory is satisfied. However, the presence of the big sphere may affect the electric field distribution and therefore, the results obtained from the electrostatic theory may not be entirely accurate.

If we want to accurately discuss the electric field distribution, we may need to use a more comprehensive theory, such as electromagnetic theory, which takes into account the effects of both electric and magnetic fields. The upper limit of frequency for applying electrostatic theory in this condition would depend on the size and properties of the objects in the vicinity of the antenna. For frequencies higher than this limit, other theories, such as electromagnetic theory, would need to be used for accurate analysis.

I hope this helps to clarify the conditions for applying electrostatic theory and the potential limitations in this scenario. Thank you for your question and interest in the topic.


Scientist