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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. 1. Hard disk drives (granular/perpendicular media) 2. Recording tape (particulate media)






2. Cracks propagate along grain boundaries.






3. Width of smallest feature obtainable on Si surface






4. 1. Stress-strain behavior is not usually determined via tensile tests 2. Material fails before it yields 3. Bend/flexure tests are often used instead.






5. Second phase particles with n > glass.






6. Ohms Law: voltage drop = current * resistance






7. Increase temperature - increase in interatomic separation - thermal expansion






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






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






10. -> fluorescent light - electron transitions occur randomly - light waves are out of phase with each other.






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






12. Reflectiviy is between 0.90 and 0.95 - Metal surfaces appear shiny - Most of absorbed light is reflected at the same wavelength (NO REFRACTION) - Small fraction of light may be absorbed - Color of reflected light depends on wavelength distribution of






13. - A magnetic field is induced in the material B= Magnetic Induction (tesla) inside the material mu= permeability of a solid






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






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






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






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. Heat capacity.....- increases with temperature -for solids it reaches a limiting value of 3R






19. Small Coercivities - Used for electric motors - Example: commercial iron 99.95 Fe






20. Light Amplification by Stimulated Emission of Radiation






21. If a material has ________ - then the field generated by those moments must be added to the induced field.






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






23. - 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






24. Materials change size when temperature is changed






25. Flaws and Defects - They concentrate stress locally to levels high enough to rupture bonds.






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






27. 1. Imperfections increase resistivity - grain boundaries - dislocations - impurity atoms - vacancies 2. Resistivity - increases with temperature - wt% impurity - and %CW






28. 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.






29. The Magnetization of the material - and is essentially the dipole moment per unit volume. It is proportional to the applied field. Xm is the magnetic susceptibility.






30. 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.






31. 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)






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






33. Typical loading conditions are _____ enough to break all inter-atomic bonds






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






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






36. Large coercivities - Used for permanent magnets - Add particles/voids to inhibit domain wall motion - Example: tungsten steel






37. Undergo little or no plastic deformation.






38. Is analogous to toughness.






39. 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






40. Growth of an oxide layer by the reaction of oxygen with the substrate - Provides dopant masking and device isolation - IC technology uses 1. Thermal grown oxidation (dry) 2. Wet Oxidation 3. Selective Oxidation






41. High toughness; material resists crack propagation.






42. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






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






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






45. Sigma=ln(li/lo)






46. No appreciable plastic deformation. The crack propagates very fast; nearly perpendicular to applied stress. Cracks often propagate along specific crystal planes or boundaries.






47. 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."






48. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






49. 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






50. 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