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I was investigating whether dry soil would conduct electricity. What I found was that at 60 Hz frequency (i.e. power line fell to the ground), dry soil is a very good conductor. But if you increase the frequency to about 1 GHz, dry soil becomes a very lossy conductor.

My question is what is the fundamental physics behind as to why these materials change electrical property depending on frequency?

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One possible answer is the skin effect. At high frequencies electricity is increasingly conducted only on the outer areas of the conductor. That means the bulk of the conductor is not used, and its apparent resistance is higher than it would be for lower frequencies or DC. This would apply to soild as well. The skin effect is due to opposing eddy currents induced by the changing magnetic field resulting from the alternating current.

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In a nutshell, the frequency of electricity has an effect on the resistivity of soil. The resistivity of soil increases when the soil has more magnetic materials such as Iron.

The ground has many minerals in it. Some of the minerals are magnetic and have dipoles. As the frequency increases the magnetic dipoles can't rotate and instead vibrate and create eddy currents. This usually happens above 2Khz for purely magnetic materials. So at 1Ghz the dry soil is a poor conductor of electricity.

Biddle ohmmeters are used to calculate the soil's conductivity and takes in other parameters. Google them for more information.

Now onto more pressing issues. Bill

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