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Field Gradients
in Two-Rod Study Case |
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Field gradients are characterized by regular and uniform changes, as in a flight of stairs.
Field gradients tend to be linear, with a constant rate of change. Conditions for field gradients
exist typically in the central area, midway between the two electrodes.
Here the current flowing through the earth reaches a stable pattern, with the
current being highly dispersed and uniform in density, and flowing straight in one direction. |
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At the surface of the earth, field gradients take on a simple linear pattern.
Field gradients tend to have low rates of change. |
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Field gradients associated with power currents tend to change levels slowly because
the earth is a large conductor,
and the current is highly dispersed. Field gradient profiles, as
shown in the figure, tend to be straight lines.
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If the physical shape taken by spreading gradients can be thought of as mountains, field
gradients are like terraces. Each step is a large expanse where the voltage changes very
slowly from one location to the next. Because of the large steps, a cow or a person cannot
straddle more than one or two steps at a time. Therefore, the voltage between field gradient
lines that a cow can simultaneously contact is necessarily small. |
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