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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. Light Amplification by Stimulated Emission of Radiation






2. 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.






3. As the applied field (H) increases the magnetic domains change shape and size by movement of domain boundaries.






4. Stress concentration at a crack tips






5. Hardness is the resistance of a material to deformation by indentation - Useful in quality control - Hardness can provide a qualitative assessment of strength - Hardness cannot be used to quantitatively infer strength or ductility.






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


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






8. Dimples on fracture surface correspond to microcavities that initiate crack formation.






9. 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)






10. Rho=F/A - tau=G/A . Depending on what angle the force is applied - and what angle the crystal is at - it takes different amounts of force to induce plastic deformation.






11. Different orientation of cleavage planes in grains.






12. 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.






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






14. (sigma)=K(sigma)^n . K = strength coefficient - n = work hardening rate or strain hardening exponent. Large n value increases strength and hardness.






15. Created by current through a coil N= total number of turns L= length of turns (m) I= current (ampere) H= applied magnetic field (ampere-turns/m) Bo= magnetic flux density in a vacuum (tesla)






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






17. Metals are good conductors since their _______is only partially filled.






18. They are used to assess properties of ceramics & glasses.






19. 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






20. 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






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






22. Undergo little or no plastic deformation.






23. Process by which geometric patterns are transferred from a mask (reticle) to a surface of a chip to form the device.






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






25. Materials change size when temperature is changed






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






27. These materials are relatively unaffected by magnetic fields.






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






29. 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.






30. 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






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. - 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






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






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






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






36. 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






37. These are liquid crystal polymers- not your normal "crystal" -Rigid - rod shaped molecules are aligned even in liquid form.


38. 1. Electron motions 2. The spins on electrons - Net atomic magnetic moment: sum of moments from all electrons.






39. 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






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






41. Specific heat = energy input/(mass*temperature change)






42. - 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






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






44. Ohms Law: voltage drop = current * resistance






45. Undergo extensive plastic deformation prior to failure.






46. Diffuse image






47. 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






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






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






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