Aluminum wiring can be used as an alternative to copper wiring. Suppose a 40-ft run of 12-gauge aluminum wire (2.05232 mm in diameter) carrying a 7.0-A current is used in a circuit. How long would it take electrons to travel the length of this run and back? There are 6.03 × 10 28 atoms in 1 m3 of aluminum, with each atom contributing three free electrons to the metal.