Using the energy band model for a semiconductor, indicate how one visualizes (a) an electron, (b) a hole, (c) donor sites, (d) acceptor sites, (e) freeze-out of majority carrier electrons at donor sites as the temperature is lowered toward 0 K, (f) freeze-out of majority carrier holes at acceptor sites as the temperature is lowered toward 0 K, (g) the energy distribution of carriers in the respective bands, (h) an intrinsic semiconductor, (i) an n-type semiconductor, (j) a p-type semiconductor, (k) a nondegenerate semiconductor, (1) a de-generate semiconductor.

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.