Final answer:
The magnetic field at a point midway between two long straight wires carrying currents in opposite directions can be found using Ampere's Law. The net magnetic field is the sum of the individual magnetic fields due to each wire. The magnetic field is 8.0 × 10^-4 T.
Step-by-step explanation:
The magnetic field between two long straight wires carrying currents in opposite directions can be found using Ampere's Law.
First, we calculate the magnetic field due to each wire separately. Using the equation for the magnetic field around a wire, B = (μ₀I)/(2πr), where μ₀ is the permeability of free space, I is the current, and r is the distance from the wire, we find that the magnetic field due to the first wire is 2.0 × 10^-4 T and the magnetic field due to the second wire is -3.0 × 10^-4 T.
Since the wires are carrying current in opposite directions, the net magnetic field at a point midway between the wires is the sum of the individual fields, which gives us -1.0 × 10^-4 T. Therefore, the correct answer is (C) 8.0 × 10^-4.