Test your basic knowledge |

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






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






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






4. 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






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






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






7. Another optical property - Depends on the wavelength of the visible spectrum.






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






9. - 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






10. High toughness; material resists crack propagation.






11. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






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






13. 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.






14. 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.






15. Light Amplification by Stimulated Emission of Radiation






16. Undergo little or no plastic deformation.






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






18. Materials change size when temperature is changed






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


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






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






22. These materials are relatively unaffected by magnetic fields.






23. To build a device - various thin metal or insulating films are grown on top of each other - Evaporation - MBE - Sputtering - CVD (ALD)






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






25. Emitted light is in phase






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






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






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






29. 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






30. 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.






31. 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






32. 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.






33. Found in 26 metals and hundreds of alloys & compounds - Tc= critical temperature = termperature below which material is superconductive.






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






35. ...occurs in bcc metals but not in fcc metals.






36. 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






37. - 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






38. 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.






39. Second phase particles with n > glass.






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






41. 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






42. Liquid polymer at room T - sandwiched between two sheets of glass - coated with transparent - electrically conductive film. - Character forming letters/ numbers etched on the face - Voltage applied disrupts the orientation of the rod- shaped molecule






43. Defines the ability of a material to resist fracture even when a flaw exists - Directly depends on size of flaw and material properties - K(ic) is a materials constant






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






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






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






47. Ohms Law: voltage drop = current * resistance






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






49. Diffuse image






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