1) A gedanken test: Instead of a wire, make the current carrying
conductor a flat sheet, infinite in extent in its dimension perpendicular
to its current direction. Now there are no edges where a charge
separation can accumulate. Turn on a B field. Will the QVxB force on the
current carriers produce a force on the current carrying sheet???
2) A possible real test: use a sheet of large, but finite dimensions; and
restrict the B field to a limited extent of the sheet. (???)