Which of the following is prohibited by the 2nd law of thermodynamics?
(a) a device that converts heat into work with 100% efficiency
(b) a device that converts work into heat with 100% efficiency.
(c) a device that uses work to supply x heat at high temperature while taking in y heat at lower temperature. where x> y.
(d) a device that converts work into heat with > 100% efficiency

Copper has free electrons per cubic meter. a 71.0-cm length of 12-gauge copper wire that is 2.05 mm in diameter carries 4.85 a of current. (a) how much time does it take for an electron to travel the length of the wire? (b) repeat part (a) for 6-gauge copper wire (diameter 4.12 mm) of the same length that carries the same current. (c) generally speaking, how does changing the diameter of a wire that carries a given amount of current affect the drift velocity of the electrons in the wire?