Halliday, Resnick & Walker — Maxwell's Equations; Magnetism of Matter: Problem 8

8 Nonuniform displacement current. Figure 32-19 shows a circular region of radius \( R = 3.00 \text{ cm} \) in which a displacement current \( i_d \) is directed out of the figure. The magnitude of the displacement current is \( i_d = (3.00 \text{ A})(r/R) \), where \( r \) is the radial distance (\( r \le R \)) from the center. What is the magnitude of the magnetic field due to \( i_d \) at radial distances (a) 2.00 cm and (b) 6.00 cm?