If 2.03×1020 electrons flow through a cross section of a 3.17 mm diameter Aluminum wire in 9.34 s, then what is the drift speed of the electrons? (The density of conduction electrons in Aluminum is n 6.00×1028 1/m3.)
Q 2.03×10^20 electrons x 1.6 x 10^-19 C/electron 32.48 Q 32.48 C I Q/t 32.48 C/ 9.34 s 3.478 amperes d 3.17 mm ; must find A A (pi)r^2 (pi) (1.585 x 10^-3 m)^2 7.8923876 × 10-6 m^2 n 6.00×1028 1/m^3 v I/neA v (3.478 amperes)/(6.00×10^28 1/m^3)(1.6x 10^-19C)( 7.8923876 × 10-6m^2) v 3.478/( 75.84 x 10^3) v 0.0458597 x 10^-3 m/s 5.8587 mm / s When electric current in a material is proportional to the voltage across it, the material is said to be ohmic, or to obey Ohm's lawA microscopic view suggests that this proportionality comes from the fact that an applied electric field superimposes a small drift velocity on the free electrons in a metalFor ordinary currents, this drift velocity is on the order of millimeters per second in contrast to the speeds of the electrons themselves which are on the order of a million meters per secondEven the electron speeds are themselves small compared to the speed of transmission of an electrical signal down a wire, which is on the order of the speed of light, 300 million meters per second Although your light turns on very quickly when you flip the switch, and you find it impossible to flip off the light and get in bed before the room goes dark, the actual drift velocity of electrons through copper wires is very slowIt is the change or signal which propagates along wires at essentially the speed of light I'd appreciate it if you voted this a 5 star answer rather than leaving it up to an ARBITRARY voteWhen you choose a best answer you get back 3 pointsYou get NO points back if you let it go to a vote.
