John M. wrote in part:
|
| Suppose I have a REAL wire with some current flowing in it.
| I challenge anyone to give me an operational procedure to
| rigorously associate a useful "vector current" with a
| specific position (or cross section or whatever) of the wire.
|
. . .
|
| As a practical matter, however, one usually comes to realize
| the advantage of associating the direction with the dl_vector
| after doing some complicated integrals using the Biot-Savart law.
|
Perhaps a glib but I think valid uptake of the challenge, is to simply
say the operational procedure is the same one you'd use to determine dl
in the Biot-Savart Law. Which we agree can be done, at least in many
situations.