Electron-Hole Pair Injection in GaAs. Assume that electron-hole pairs are injected into n type GaAs (Eg = 1.42 eV, me ~ 0.07 mo, mu 0.50 rno) at a rate R = 1023/cms_s. The thermal 10-11 cm2/s and T 300° K, determine: (a) The equilibrium concentration of holes po (b) The recombination lifetime τ (c) The steady-state excess concentration Δn. (d) The separation between the quasi-Fermi levels Efe-Efv, assuming that T = 00 K.

Plan an experiment to measure the surface tension of a liquid similar to water. if necessary, review the ncfmf video surface tension for ideas. which method would be most suitable for use in an undergraduate laboratory? what experimental precision could be expected?

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2

1in2 processor chip can be modelled as an isothermal plane wall of silicon, isothermal on both sides. the power input to the bottom of the plane wall, or the processing power of the chip, often called the thermal design power (tdp), is 100w. assume the periphery is adiabatic. the silicon is 400 microns thick. the temperature at the junction, or in this case on the bottom of the isothermal plane wall, is 85°c. what is the top surface temperature, assuming that the only mode of heat transfer is conduction