Halliday, Resnick & Walker — Current and Resistance: Problem 48

48 Figure 26-27a gives the magnitude \(E(x)\) of the electric fields that have been set up by a battery along a resistive rod of length 9.00 mm (Fig. 26-27b). The vertical scale is set by \(E_s = 8.00 \times 10^3 \text{ V/m}\). The rod consists of three sections of the same material but with different radii. (The schematic diagram of Fig. 26-25b does not indicate the different radii.) The radius of section 3 is 1.70 mm. What is the radius of (a) section 1 and (b) section 2?