Which of the following is true of semiconductors?
a. exposing a crystal of a semiconductor to heat or light starts displacing valence electrons, which then move throughout the crystal.
b. a material is classified as a semiconductor if its resistance to the flow of electric current is too low to permit it to be called a conductor.
c. neither free electrons nor holes are considered charge carriers in a semiconductor.
d. gold and silver are important semiconductors

An ideal otto cycle has a compression ratio of 8. at the beginning of the compression process, air is at 95 kpa and 27°c, and 750 kj/kg of heat is transferred to air during the constant-volume heat-addition process. assuming constant specific heats at room temperature, determine (a) the pressure and temperature at the end of the heat-addition process, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle. (4390 kpa, 1730 k; 423 kj/kg; 56.4%; 534 kpa)