Arfa Daily wrote:
snip
Now, I can see what the article (and you) are saying, but what I didn't
understand was the mechanism that caused these "expanding concentric
circles" of potential difference,

Does the article imply or depict a non-linear potential gradient?

which would be close enough together -
what's the length of a step, 45cm (18"") perhaps? - to allow you to step on
two of them together. At what speed are they expanding ? Presumably, slowly
enough to allow you to step on two for long enough to fry you ? Or has the
person writing the article, or the artist, got it basically wrong, or are
attempting to over-simplify or create a non-realistic model that might
better allow a semi-layman to understand the concept?

I would expect that all of this would be highly dependent on soil
conductivity and the underlying geology and that models must exist for
a variety of soil types, locations and conditions as this must be
a topic of importance to utility companies and insurers. In
rural areas where "stray voltage" complaints are encountered, the
utilities must have some good data. I suspect that natural resource
exploration businesses also have data and instrumentation.

The essential concern is for a high radial potential gradient from the
point of the downed line; I wonder if there are electrolysis effects
that would decrease soil resistance over time that could cause
an "expanding" gradient.

Michael