Ap-n step junction in si has 1018 cm-3 net acceptors on the p side and 1014 cm-3 net donors on the n side. assume t = 300k, ni = 1.5 x 1010cm-3, find (a) the built-in potential and (b) extent of depletion region on n and p side. (c) explain how the built-in potential is related to the fermi level and what happens to vbi as a function of temperature in the range 30k to 500k.

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)