Halliday, Resnick & Walker — Magnetic Fields Due to Currents: Problem 45

45 In Fig. 29-50, two long straight wires are perpendicular to the page and separated by distance \( d_1 = 0.75 \text{ cm} \). Wire 1 carries \( 6.5 \text{ A} \) into the page. What are the (a) magnitude and (b) direction (into or out of the page) of the current in wire 2 if the net magnetic field due to the two currents is zero at point \( P \) located at distance \( d_2 = 2.50 \text{ cm} \) from wire 2? If the current in wire 2 is then reversed, what are the (c) size and (d) direction of the net field at point \( P \)?