일반물리학 2 — Induction and Inductance: Problem 19

19 Two identical long wires of radius a = 0.530 mm are parallel and carry identical currents in opposite directions. Their center-to-center separation is d = 20.0 cm. Neglect the flux within the wires but consider the flux in the region between the wires. What is the inductance per unit length of the wires?