regarding plane waves theory and their properties, for lossy media (conductors) in different books appear a formula that represent alfa y beta constants in the followig way:(adsbygoogle = window.adsbygoogle || []).push({});

alfa = beta = root square( pi*frequency*mu*sigma) valid for good

conductors (high loss material)

I have checked this formula in different books and it works well, and

it's used further to calculate skin effect as well

My question arises from one conclusion derived from the formula, that I

found in just a specific book (David Cheng's Fundamentals of

engineering electromagnetics).

In that book the author says:

velocity of propagation = omega / beta

For copper (good conductor):

sigma = 5.8 * 10 exp 7

mu = 4 *pi *10 exp -7

and therefore v = 720 m/sec. @ f = 3 Mhz.

so the velocity of propagation is << c

I am confused with the final result, because I've checked the formula, and the math in the example is right, but I know that in a copper transmission line, the velocity of propagation is about 2/3 c = 200,000 km/sec.

The formula appears in different books, but the specific example just

appears in Cheng's book

I think the application for the example is valid in a different situation,

but I can't figure out which

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# Velocity of propagation in lossy media

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