일반물리학 2 — Induction and Inductance: Problem 25

25 A length of copper wire carries a current of 3.5 A uniformly distributed through its cross section. Calculate the energy density of (a) the magnetic field and (b) the electric field at the surface of the wire. The wire diameter is 2.5 mm, and its resistance per unit length is 3.3 \(\Omega\)/km.