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






2. # of thermally generated electrons = # of holes (broken bonds)






3. Second phase particles with n > glass.






4. 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






5. Is analogous to toughness.






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






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






8. The ability of a material to transport heat - Atomic Perspective: Atomic vibrations and free electrons in hotter regions transport energy to cooler regions - Metals have the largest values






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






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






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






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






13. 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






14. 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






15. Becomes harder (more strain) to stretch (elongate)






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






17. 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.






18. 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.






19. - 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






20. This strength parameter is similar in magnitude to a tensile strength. Fracture occurs along the outermost sample edge - which is under a tensile load.






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






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






23. Process by which metal atoms diffuse because of a potential.






24. 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.






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






26. Failure under cyclic stress 1. It can cause part failure - even though (sigma)max < (sigma)c 2. Causes ~90% of mechanical engineering failures.






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






28. 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.






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






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






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






32. Ohms Law: voltage drop = current * resistance






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






34. Degree of opacity depends on size and number of particles - Opacity of metals is the result of conduction electrons absorbing photons in the visible range.






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






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






37. - 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






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






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






40. Occur when lots of dislocations move.






41. Different orientation of cleavage planes in grains.






42. Cracks pass through grains - often along specific crystal planes.






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






44. These materials are relatively unaffected by magnetic fields.






45. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






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






47. 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






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






49. Materials change size when temperature is changed






50. 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.