## College Physics (4th Edition)

We can write an expression for the drift speed: $v_d = \frac{I}{n~q~A} = \frac{I}{n~q~\pi~r^2}$ $I$ is the current $n$ is the number of electrons per unit of volume $q$ is the charge of one electron $A$ is the cross-sectional area $r$ is the cross-sectional radius We can find the drift speed $v_d$: $v_d = \frac{I}{n~q~\pi~r^2}$ $v_d = \frac{10.0~A}{(8.47\times 10^{28}~m^{-3})(1.6\times 10^{-19}~C)~(\pi)~(5.00\times 10^{-4}~m)^2}$ $v_d = 9.395\times 10^{-4}~m/s$ We can find the time it takes to move 1.00 meter: $t = \frac{d}{v_d}$ $t = \frac{1.00~m}{9.395\times 10^{-4}~m/s}$ $t = 1064~s$ It takes 1064 seconds for a conduction electron to move 1.00 meter along the wire.