일반물리학 2 — Magnetic Fields Due to Currents: Problem 63

63 At a certain location in the Philippines, Earth’s magnetic field of $39\text{ \(\mu\)T}$ is horizontal and directed due north. Suppose the net field is zero exactly $2.0\text{ cm}$ above a long, straight, horizontal wire that carries a constant current. What are the (a) magnitude and (b) direction of the current?