finalfall2000

# Finalfall2000 - ~ ~ ~ ENSC.Answer 3313 any Fall 20 2000 Name FINAL Questions only 2 points each European television sets generate25 images per

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~ FINAL ~ ENSC 3313, Fall 2000 Name .Answer any 20 Questions only, 2 points each. European television sets generate 25 images per second (as compared to 30 images/sec. for US television sets). Calculate the relaxation time of the phosphor used in European TV sets if 80% of each image is to have faded before the next image is produced. = Ioe-tlA -0.4 sec/A O.2=e -0.04 ~ A= = 0.025 sec 2. The energy gap in pure Si is 0.17 6 x 10-18 J. What wave length of light is required to promote an electron across this gap? Report your answer in nm. k = 13.8 x 10-24 J/K h = 0.662 x 10-33 J-sec c = 3.0 x 108 m/sec c v=- A E=hv hc A = hc E A= ~ 0.176x 10-181 = 1.13 x 103 nrn Identify the location of the 2 fold symmetry axes in a cube. How many are there? 3. 6. Connect the mid-points of the opposite edges!

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~8, Identtry the lattice plane and lattice direction sketched. ( ~ , z -1 ..-1/2 -+ With origin at 0, the plane interception on the axes are 1, 1/2,1. Taking reciprocals, the plane is (121). Going start to end of line in plane, we travel lx, Oy , -1 z. Hence direction is [1 ° T] .Checking hu + kv + I w = ° is satisfied (the direction lies in the plane). x y / / / ; " " ... 5. Cr fonns a BCC crystal, has an atomic mass of 52.00 amu, an ionic radius of 0.063, nm and an atomic radius of 0.125 Dm. Predict the density ofCr in gm/cm3. Avogadro's number is 6.023' x 1023. ~ = 1 unit cell 6. The figure below shows the grain structure ofW (200x). Please fmd the ASTM grain size number. I count 16 grains in a square 1 " , 16 10-4 in2 64 grains 10-4 in2 =26 ~n-l=6 = ~
7. .:9. D = D eRr o 2 = 7.69xl0-s~ s D(1200°C) = s The figure below shows the stress-strairi behavior of a brass specimen. Calculate the (a) elastic modulus and (b ) the yield strength at an offset of 0.2%. Report your answers in English units. 8. a) E = ~ in the elastic region e = 20,000 psi 0.0016 = 12.5 x 106 Dsi b) Sy=~ 0.10 0.20 Strain 0.30 0.40 0 I showed this diagram on the overhead projector. (a) What is it illustrating? (b) For what material is it appropriate? ( c ) What do the "x" markings represent? ( d) What type of "work" does the bottom curve correspond to? 9. a) v ariation of 0" / E behavior with temperature. Highest T curve at bottom. b) Brittle at low T, hence steel. c) Yield stress d) No strain hardening, so hot work. . STRFSS

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## This note was uploaded on 01/10/2012 for the course ENSC 3313 taught by Professor Staff during the Fall '11 term at Oklahoma State.

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Finalfall2000 - ~ ~ ~ ENSC.Answer 3313 any Fall 20 2000 Name FINAL Questions only 2 points each European television sets generate25 images per

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