일반물리학 2 — Current and Resistance: Problem 45

45 What is the current in a wire of radius $R = 2.67\text{ mm}$ if the magnitude of the current density is given by (a) $J_a = J_0 r/R$ and (b) $J_b = J_0(1 - r/R)$, in which $r$ is the radial distance and $J_0 = 5.50 \times 10^4\text{ A/m}^2$? (c) Which function maximizes the current density near the wire's surface?