This came up at mythbusters, a question about the propragation of currrent from a switch that is a long distance from a DC power source. Assume the wires are sufficiently large (capcitance wise): 1 mile long wire connected to positive terminal of DC power source at one end, open switch at other end, with DC LEDs in series as part of the wire 1 mile long wire connected to negative terminal of the same DC power source as above at one end, to the same open switch as above at other end, with DC LEDs in series as part of the wire. Assume that the state of the system has stabilized, and an idealized DC power source. The postive side of the switch has positive potential (insufficient electrons), the negative side of the switch has negative potential (excess electrons). Now close the switch. Does the potential at the switch result in immediate current flow at the switch, propagating back via both wires to the battery, so that the LEDs light up in sequence at the rate of propagation?