Asemiconductor has a electron band structure e(k) = (4k 2 + 5) ev, where k has units of ˚a−1 (1˚a = 1 × 10−10 m). calculate the effective mass of the electrons. why is the effective mass different from the actual electron mass of 9.1x 10-31 kg ?

The mass flow rate of the fluid remains constant in all steady flow process. a)- true b)- false

Select any two (2) areas of applications of chain-drive. (clo4) a)-permanent lubrication necessary b)-hydraulic forklift truck operation c)-rigging and heavy moving materials d)-relatively high maintenance costs e)-costlier than belt drives

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.