(1) current density: j = i0/π a 2, so the electric field intensity e = ρ j = ρ i0/π a 2 is in the same direction as i.

(2) H=I0/2πr direction is perpendicular to I0.

(3) s = exh = ρ i0 2/2π 2a 2r direction is perpendicular to the conductor surface.

(4) The energy consumed by a conductor with a length of L and a radius of R is W = S 2 π rl, that is, W is equal to the integral of S on the surface of the conductor.