#mse45

Prof L. M. [#mse45 lm], fall 2021 [#fall2021]

hw1: 1, 3, 4, 5, 6, 7 /7 [#mse45 hw1, #mse45 lm hw1]

hw2: i basically bombed hw2 w a 61/100 so,,

hw3: 3, 5, 6 /6 [#mse45 hw3, #mse45 lm hw3]

hw4: 3, 4, 5, 6 /6 [#mse45 hw4, #mse45 lm hw4]

hw5: 1, 2, 3, 4, 5, 6 /7 [#mse45 hw5, #mse45 lm hw5]

hw6: all 7 qns [#mse45 hw6, #mse45 lm hw6]

hw7: all 7 qns [#mse45 hw7, #mse45 lm hw7]

hw8: all 7 qns [#mse45 hw8, #mse45 lm hw8]

hw9: all 8 qns [#mse45 hw9, #mse45 lm hw9]

hw10: all 7 qns [#mse45 hw10, #mse45 lm hw10]

MSE 45L [#mse45L]

lab 2 : Recovery, Recrystallization, & Grain Growth intro, disc [#mse45 lab2, #mse45L lab2]

lab 3 : Binary Alloy Phase Diagrams abstract, intro, disc [#mse45 lab3, #mse45L lab3]

lab 4 : Heat Treatment of Steel abstract, disc [#mse45 lab4, #mse45L lab4]

lab 5 : Uniaxial Tensile Test intro [#mse45 lab5, #mse45L lab5]

lab 6 : Electronic Properties of Materials abstract, intro, disc [#mse45 lab6, #mse45L lab6]

Q7. (12 pts.) A coil of wire 0.5 m long and having 20 turns carries a current of 1.0 A. Answer the following: (4 pts.) Compute the flux density if the coil is within a vacuum. (4 pts.) A bar of an iron–silicon alloy, the B-H behavior for which is shown in Figure 20.29, is positioned within the coil. What is the flux density within this bar? (4 pts.) Suppose that a bar of molybdenum is now situated within the coil. What current must be used to produce the same B field in the Mo as was produced in the iron–silicon alloy (part b) using 1.0 A?

Figure 20.29

Table 20.2

12/12

Q6. (14 pts.) Assume there exists some hypothetical metal that exhibits ferromagnetic behavior and that has (1) a simple cubic crystal structure, (2) an atomic radius of 0.125 nm, and (3) a saturation flux density of 0.85 T. Determine the number of Bohr magnetons per atom for this material.

14/14

Q5. (12 pts) The magnetic flux density within a bar of some material is 0.630 T at an H field of 5 × 10^5 A/m. Compute the following for this material: (4 pts.) The magnetic permeability. (4 pts.) The magnetic susceptibility. (4 pts.) What type(s) of magnetism would you suggest is (are) being displayed by this material? Why?

12/12

*for (c), its better to say paramagnetic since Xm is small and positive

Q4. (20 pts.) A charge of 2.0 × 10-10 C is to be stored on each plate of a parallel-plate capacitor having an area of 650 mm2 (1.0 in2) and a plate separation of 4.0 mm (0.16 in). Answer the following: (4 pts.) What voltage is required if a material having a dielectric constant of 3.5 is positionedwithin the plates? (4 pts.) What voltage would be required if a vacuum were used? (4 pts.) What are the capacitances for parts (a) and (b)? (4 pts.) Compute the dielectric displacement for part (a). (4 pts.) Compute the polarization for part (a).

20/20

Q3. (12 pts.) For CaO, the ionic radii for Ca2+ and O2- ions are 0.100 and 0.140 nm, respectively. If an externally applied electric field produces a 5% expansion of the lattice, compute the dipole moment for each Ca2+-O2- pair. Assume that this material is completely unpolarized in the absence of an electric field.

10/12 *charge is ±2 so Q should be 2*e

Q2. (14 pts.) a. (6 pts.) A parallel-plate capacitor using a dielectric material having an εr of 2.2 has a plate spacing of 2 mm (0.08 in.). If another material having a dielectric constant of 3.7 is used and the capacitance is to be unchanged, what must be the new spacing between the plates? b. (8 pts.) A parallel-plate capacitor with dimensions of 38 mm by 65 mm and a plate separation of 1.3 mm must have a minimum capacitance of 70 pF (7 × 10-11 F) when an ac potential of 1000 V is applied at a frequency of 1 MHz. Which of the materials listed in Table 18.5 are possible candidates? Why?

Table 18.5

14/14

Q1. (16 pts.) For intrinsic semiconductors, the intrinsic carrier concentration ni depends on the temperature as 𝑛𝑖 ∝ 𝑒𝑥𝑝 (− 𝐸𝑔/2𝑘𝑇). Using this fact and the data in Figure 18.16 for silicon and germanium, determine the band gap energies of these materials.

Figure 18.16

16/16