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






2. 1. Necking 2. Cavity formation 3. Cavity coalescence to form cracks 4. Crack propagation (growth) 5. Fracture






3. 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






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






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






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






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






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






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

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






11. 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






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






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






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






15. 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






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






17. A three terminal device that acts like a simple "on-off" switch. (the basis of Integrated Circuits (IC) technology - used in computers - cell phones - automotive control - etc) - If voltage (potential) applied to the "gate" - current flows between th






18. 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.






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






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






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






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






23. Second phase particles with n > glass.






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






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






26. 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






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






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






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






30. 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)






31. 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.






32. Is analogous to toughness.






33. 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.






34. Sigma=ln(li/lo)






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






36. Undergo extensive plastic deformation prior to failure.






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






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






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






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






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






42. Stress concentration at a crack tips






43. - 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






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






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






46. 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.






47. 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.






48. 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.






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






50. High toughness; material resists crack propagation.