Chapter 1 - 1.2 - Problems - Circuits, Currents, and Voltages - Page 35: P1.17

$v = 4.02\times 10^{-4}~m/s$

Let $N$ be the number of electrons per $m^3$ $i(t) = v~A~q~N$ We can find the average velocity $v$ of the electrons. $v = \frac{i}{A~q~N}$ $v = \frac{i}{\pi~r^2~q~N}$ $v = \frac{15~\sqrt{2}~C/s}{\pi~(1.025\times 10^{-3}~m)^2(1.6\times 10^{-19}~C)(10^{29}~electrons/m^3)}$ $v = 4.02\times 10^{-4}~m/s$