In this question I am referring to this article.
At first I was looking for a physical explanation of the fact that energy or the signal, respectively, travels much faster through a wire than the electrons inside of it do (drift velocity).
After reading the article, I understand that neither the amount of current flowing around, nor the voltage between two points is responsible for the speed of the energy transfer. It’s rather the material surrounding the conductor that’s affecting the propagation speed with its permittivity and permeability. Is this correct up to here?
Figure 4, however, makes me wonder two things:
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Of course, every point of a conductor has the same potential and inside of conductors, there won't be an electrical field. But why is that? You learn that since we're inside a conductor, a current will work against every potential difference that might exist between two connected points, thereby compensating it. But isn't current (the actual flow of charge carriers) incredibly slow? And doesn't this make an immediate compensation impossible?
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Now let's say two connected points will always have the same potential. When talking about RF engineering, you learn that as soon as the wavelength becomes of the order of the physical wire's length, you will measure different voltages across one single wire. How does this correspond to the idea of an immediate response of the charge carriers?
What am I missing?
Best Answer
To try to answer your actual questions:
1 - Current is not "the actual flow of charge carriers" any more than sound is the actual movement of air molecules. To equalize a potential difference between points A and B, it is not necessary for any of the charge carriers originally at point A to show up at point B (just as none of the air molecules at a sound source actually make it to your ear). Maybe a better analogy is turning on the faucet at the kitchen sink. When you do this, the pressure at the spout is less than the pressure in the water main and this forces water to come out. But, in the time it takes to fill a glass, no water that was previously in the main will make it out of the spout.
2 - There is no such thing as an "immediate response of the charge carriers". Nothing "real" moves from place to place faster than the speed of light. Thus, when you consider frequencies with wavelengths comparable to the physical size of your conductor, potentials and currents will be different at different places. Don't let anyone tell you otherwise.