Chapter 21 - Electric Current and Direct-Current Circuits - Problems and Conceptual Exercises - Page 761: 117

(a) $2.4W/m$ (b) $2.0W/m$

(a) We know that $\frac{P}{L}=I^2(\rho/A)$ We plug in the known values to obtain: $\frac{P}{L}=(35A)^2(1.68\times 10^{-8}\Omega m/8.45\times 10^{-6}m^2)$ $\frac{P}{L}=2.4W/m$ (b) We know that $\frac{P}{L}=I^2(\frac{\rho}{A})$ We plug in the known values to obtain: $\frac{P}{L}=(25A)^2(1.68\times 10^{-8}\Omega m/5.27\times 10^{-6}m^2)$ $\frac{P}{L}=2.0W/m$