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






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






3. 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






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






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






6. Cracks propagate along grain boundaries.






7. 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.






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






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






10. 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






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






12. Because of ionic & covalent-type bonding.






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






14. Sigma=ln(li/lo)






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






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






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






18. Materials change size when temperature is changed






19. 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.






20. Second phase particles with n > glass.






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






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






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






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






25. Stress concentration at a crack tips






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






27. 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






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






29. 1. Ductility- % elongation - % reduction in area - may be of use in metal forming operations (e.g. - stretch forming). This is convenient for mechanical testing - but not very meaningful for most deformation processing. 2. Toughness- Area beneath str






30. Undergo little or no plastic deformation.






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






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






33. 1. Data for Pure Silicon - electrical conductivity increases with T - opposite to metals






34. 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.






35. Cp: Heat capacity at constant pressure Cv: Heat capacity at constant volume.






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






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






38. 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.






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






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






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






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






43. 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."






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






45. 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.






46. Light Amplification by Stimulated Emission of Radiation






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






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






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






50. Occur when lots of dislocations move.