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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. 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.






2. 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






3. 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.






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






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






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






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






8. 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.






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






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






11. Stress concentration at a crack tips






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






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






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






15. Occur when lots of dislocations move.






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






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






18. 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)






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






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






21. Emitted light is in phase






22. - 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






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






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






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






26. 1. Metals: Thermal energy puts many electrons into a higher energy state. 2. Energy States: Nearby energy states are accessible by thermal fluctuations.






27. Growing interconnections to connect devices -Low electrical resistance - good adhesion to dielectric insulators.






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






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






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






31. 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






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






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

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






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






36. Materials change size when temperature is changed






37. 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






38. 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






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






40. These materials are relatively unaffected by magnetic fields.






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






42. Different orientation of cleavage planes in grains.






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






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






45. 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.






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






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






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






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






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