The density of mobile electrons in copper metal is 8.4 x 1028 m'3. Suppose that i = 2.1 x 1013 electrons/s are drifting through a copper wire. (This is a typical value for a simple circuit.) The diameter of the wire is 3.0 mm. In this case, about how many minutes would it take for a single electron in the electron sea to drift from one end to the other end of a wire 25 cm long? (A puzzle: if the drift speed is so slow, how can a lamp light up as soon as you turn it on? We'll come back to this in the next chapter.) Additional Materials L7] eBook