Example 7.1: Ohm's law

Question: What is the resistance at $0^\circ$C of a $1.0$m long piece of no. 5 gauge copper wire (cross-sectional area $16.8\,{\rm mm}^2$)? What voltage must be applied across the two ends of the wire to produce a current of 10A through it?
 
Answer: Using the basic equation $R=\rho\,L/A$, and the value of $\rho$ for copper given in Tab. 2, we have

$$R = \frac{(1.7\times 10^{-8})\,(1.0)}{(16.8\times 10^{-6})} = 1.0\times 10^{-3}\, \Omega.$$

Using Ohm's law $V=I\,R$, we obtain

$$V = (10)\, (1.0\times 10^{-3}) = 1.0\times 10^{-2} \,{\rm V}.$$