   # Engineering Materials Week 13

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Engineering Materials Week 13
18.7 How does the electron structure of an isolated atom differ from that of a solid material?
For an isolated atom, there exist discrete electron energy states each state may be occupied by two electrons, which must have opposite spins. An electron band structure is found for solid materials; within each band exist closely spaced yet discrete electron states, each of which may be occupied by , two electrons, having opposite spins.
18.15 Determine the electrical conductivity of a Cu-Ni alloy that has a tensile strength of 275 MPa (40,000 psi).

18.21 At room temperature the electrical conductivity of PbS is 25, whereas the electron and hole mobilities are 0.06 and 0.02, respectively. Compute the intrinsic carrier concentration for PbS at room temperature.

18.32 Calculate the conductivity of intrinsic silicon at 80°C.

18.40 Estimate the electrical conductivity, at 135°C, of silicon that has been doped with of aluminum atoms.

18.51 Consider a parallel-plate capacitor having an area of 3225,a plate separation of 1 mm, and with a material having a dielectric constant of 3.5 positioned between the plates.(a) What is the capacitance of this capacitor? (b) Compute the electric field that must be applied for to be stored on each plate.

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