Tuesday, March 20, 2018

Tale Spin


\(\nabla.A\ne\nabla.(-A)\),



refers to a point at the periphery of the spinning field, \(P\) and not at its center \(C\).  The flow of \(E\) at the center is reversed when a negative sign is applied.

Strictly speaking,

\(\nabla.A\)

does not represent the effect of spinning \(E\) at point \(P\).  Neither does,

\(-\cfrac{\partial E}{\partial t}\)

nor the more familiar,

\(-\cfrac{\partial B}{\partial t}\)

represents the spinning end of a field \(B\) centered at \(C\).  It is the negative rate of change with time of \(B\) at a fixed arbitrary point \(P\).

Lunch!