Since there are few truly "long" straight wires in the real world
(power lines are an exception) the 1/r dependence that we like to derive
in the elementary course really holds only if you are close to the wire.
The key point is that magnetic field generated by the time varying
electric field between the plates of a capacitor can be shown to be a true
radiation field (1/r dependence from a POINT source) using the most
elementary of mathematics. An oscillating current in a finite circuit, of
course, also produces radiation fields....but showing requires more math
than most of my intro students have.
Hope that clears up what I was trying to get across....
Mark
Dr. Mark H. Shapiro
Physics Department
California State University, Fullerton
P.O. Box 6866
Fullerton, California 92834-6866