일반물리학 2 — Current and Resistance: Problem 46

46 A certain cylindrical wire carries current. We draw a circle of radius r around its central axis in Fig. 26-26a to determine the current i within the circle. Figure 26-26b shows current i as a function of \(r^2\). The vertical scale is set by \(i_s = 4.0 \text{ mA}\), and the horizontal scale is set by \(r_s^2 = 8.0 \text{ mm}^2\). (a) Is the current density uniform? (b) If so, what is its magnitude? (c) What is the current between \(r = 0\) and \(r = 2.0 \text{ mm}\)?