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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. These materials are relatively unaffected by magnetic fields.






2. A high index of refraction (n value) allows for multiple internal reactions.






3. Superconductors expel magnetic fields - This is why a superconductor will float above a magnet.






4. Dramatic change in impact energy is associated with a change in fracture mode from brittle to ductile.






5. Impurities added to the semiconductor that contribute to excess electrons or holes. Doping = intentional impurities.






6. Is reflected - absorbed - scattered - and/or transmitted: Io=It+Ia+Ir+Is






7. Measures Hardness - No major sample damage - Each scales runs to 130 but only useful in range 20-100 - Minor load is 10 kg - Major load: 60 kg (diamond) - 100 kg (1/16 in. ball) - 150 kg (diamond)






8. Allows you to calculate what happened G=F' x cos(lambda) - F=F' x cos(phi)






9. Cracks propagate along grain boundaries.






10. 1. Yield = ratio of functional chips to total # of chips - Most yield loss during wafer processing - b/c of complex 2. Reliability - No device has infinite lifetime. Statistical methods to predict expected lifetime - Failure mechanisms: Diffusion reg






11. Stress concentration at a crack tips






12. Increase temperature - no increase in interatomic separation - no thermal expansion






13. 1. Insulators: Higher energy states NOT ACCESSIBLE due to gap 2. Semiconductors: Higher energy states separated by a smaller gap.






14. A three terminal device that acts like a simple "on-off" switch. (the basis of Integrated Circuits (IC) technology - used in computers - cell phones - automotive control - etc) - If voltage (potential) applied to the "gate" - current flows between th






15. heat flux = -(thermal conductivity)(temperature gradient) - Defines heat transfer by CONDUCTION

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16. - The emission of light from a substance due to the absorption of energy. (Could be radiation - mechanical - or chemical energy. Could also be energetic particles.) - Traps and activator levels are produced by impurity additions to the material - Whe






17. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low






18. Ability to transmit a clear image - The image is clear.






19. There is always some statistical distribution of flaws or defects.






20. Elastic means reversible! This is not a permanent deformation.






21. 1. Fluorescent Lamp - tungstate or silicate coating on inside of tube emits white light due to UV light generated inside the tube. 2. TV screen - emits light as electron beam is scanned back and forth.






22. Different orientation of cleavage planes in grains.






23. Occurs at a single pore or other solid by refraction n = 1 for pore (air) n > 1 for the solid - n ~ 1.5 for glass - Scattering effect is maximized by pore/particle size within 400-700 nm range - Reason for Opacity in ceramics - glasses and polymers.






24. Width of smallest feature obtainable on Si surface






25. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






26. A measure of the ease with which a B field can be induced inside a material.






27. The size of the material changes with a change in temperature - polymers have the largest values






28. The magnetic hysteresis phenomenon: Stage 1: Initial (unmagnetized state) Stage 2: Apply H - align domains Stage 3: Remove H - alignment remains => Permanent magnet Stage 4: Coercivity - Hc negative H needed to demagnitize Stage 5: Apply -H - align d






29. Transmitted light distorts electron clouds - The velocity of light in a material is lower than in a vacuum - Adding large ions to glass decreases the speed of light in the glass - Light can be "bent" (or refracted) as it passes through a transparent






30. Allows flow of electrons in one direction only (useful to convert alternating current to direct current) - Result: no net current flow






31. A parallel-plate capacitor involves an insulator - or dielectric - between two metal electrodes. The charge density buildup at the capacitor surface is related to the dielectric constant of the material.






32. 1. Diamagnetic (Xm ~ 10^-5) - small and negative magnetic susceptibilities 2. Paramagnetic (Xm ~ 10^-4) - small and positive magnetic susceptibilities 3. Ferromagnetic - large magnetic susceptibilities 4. Ferrimagnetic (Xm as large as 10^6) - large m






33. (sigma)=F/Ai (rho)=(rho)'(1+(epsilon))






34. Measures impact energy 1. Strike a notched sample with an anvil 2. Measure how far the anvil travels following impact 3. Distance traveled is related to energy required to break the sample 4. Very high rate of loading. Makes materials more "brittle."






35. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






36. 1. Tensile (opening) 2. Sliding 3. Tearing






37. 1. General yielding occurs if flaw size a < a(critical) 2. Catastrophic fast fracture occurs if flaw size a > a(critical)






38. The ability of a material to be rapidly cooled and not fracture






39. Not ALL the light is refracted - SOME is reflected. Materials with a high index of refraction also have high reflectance - High R is bad for lens applications - since this leads to undesirable light losses or interference.






40. Without passing a current a continually varying magnetic field will cause a current to flow






41. Transformer cores require soft magnetic materials - which are easily magnetized and de-magnetized - and have high electrical resistivity - Energy losses in transformers could be minimized if their cores were fabricated such that the easy magnetizatio






42. Resistance to plastic deformation of cracking in compression - and better wear properties.






43. Diffuse image






44. Plastic means permanent! When a small load is applied - bonds stretch & planes shear. Then when the load is no longer applied - the planes are still sheared.






45. Digitalized data in the form of electrical signals are transferred to and recorded digitally on a magnetic medium (tape or disk) - This transference is accomplished by a recording system that consists of a read/write head - "write" or record data by






46. Wet: isotropic - under cut Dry: ansiotropic - directional






47. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






48. These materials are "attracted" to magnetic fields.






49. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






50. For a metal - there is no ______ - only reflection