Halliday, Resnick & Walker — Magnetic Fields Due to Currents: Problem 49

49 Figure 29-54 shows two current segments. The lower segment carries a current of \(i_1 = 0.40 \text{ A}\) and includes a semicircular arc with radius \(5.0 \text{ cm}\), angle \(180^\circ\), and center point \(P\). The upper segment carries current \(i_2 = 3i_1\) and includes a circular arc with radius \(4.0 \text{ cm}\), angle \(120^\circ\), and the same center point \(P\). What are the (a) magnitude and (b) direction of the net magnetic field \(\vec{B}\) at \(P\) for the indicated current directions? What are the (c) magnitude and (d) direction of \(\vec{B}\) if \(i_1\) is reversed?