Halliday, Resnick & Walker — Maxwell's Equations; Magnetism of Matter: Problem 45

45 A silver wire has resistivity \(\rho = 1.62 \times 10^{-8} \Omega \cdot \text{m}\) and a cross-sectional area of \(5.00 \text{ mm}^2\). The current in the wire is uniform and changing at the rate of \(2000 \text{ A/s}\) when the current is \(54.0 \text{ A}\). (a) What is the magnitude of the (uniform) electric field in the wire when the current in the wire is \(100 \text{ A}\)? (b) What is the displacement current in the wire at that time? (c) What is the ratio of the magnitude of the magnetic field due to the displacement current to that due to the current at a distance \(r\) from the wire?