In the tight binding approximation, atomic orbitals lead to the formation of band- structure when many atoms are brought together. magnesium has an atomic con- figuration of 1s22s22p3s2. do you expect magnesium to be a metal, or insulator? explain why. (b) the energy e of a hole in the valance band of a semiconductor is related to its wave vector k by e= a cosa ka, where a is a constant and a is the atomic lattice spacing. if a = 2 x 10-1°m then the fermi wave vector is 2.618 x 10°m-1 and the fermi energy is lev. determine the effective mass of holes at the fermi level. (c) different atoms have different magnitudes and even sign of the hall coefficient. for instance, au is -0.72 and be is +2.44. what properties determine the sign and magnitude of the hall coefficient? (d) a tiny grain of metal is found to exhibit the phenomena of coulomb blockade at room temperature. write down the conditions for coulomb blockade in terms of the charging energy e and and tunnel resistance rt. estimate the size of the grain.

What color of light must blue light mix with to create white light? a. yellow b. white c. blue d. green

In a steady-flow steam power plant system, two adiabatic high-pressure and low-pressure turbines ane used to generate power. superheated steam enters the high-pressure turbine at 8 mpa and 550°c. the steam expands in the high-pressure turbine to a saturated vapor at 3 mpa. in order to increase the powe generation of the power plant, another steam turbine working in a lower pressure ranges is deployed. the outlet vapor from the first turbine is heated up at a boiler to the temperature of 500 c at the constant pressure of first turbine's outlet (3 mpa). then, the vapor enters the second turbine and produces extra work. the exit conditions of the second turbine are 5o kpa and 90 percent quality. if the total power output of the power plant is 25 mw, determine a) the mass flow rate of the water (kg/s). b) heat transfer rate in the boiler (mw). (30 points) 3 mpa 00 c 8 mpa s0 c high pres turbine low pres boiler turbine 50 kpa 3 mpa 09 saturated vapor t heat engine, shown in the figure, operates between high temperature and low temperature of through a heat 4. a carnot tn and tu respectively. this heat engine receives energy from a heat reservoir at t exchanger where the heat transferred is proportional to the temperature difference as ? = k (z,-7, ). it rejects heat at a given low temperature tl. to design the heat engine for maximum work output, find the high temperature, th, as a function of tes and t. (15 points) qe

The photo shows sugar dissolved into a solution with excess sugar at the bottom of the jar this type of solution is classified as a. unsaturated b. compound c. saturated d. plasma