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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. These materials are "attracted" to magnetic fields.






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






3. Energy is stored as atomic vibrations - As temperature increases - the average energy of atomic vibrations increases.






4. Diffuse image






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






6. 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






7. Loss of image transmission - You get no image - There is no light transmission - and therefore reflects - scatters - or absorbs ALL of it. Both mirrors and carbon black are opaque.






8. 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






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






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






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

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12. Ohms Law: voltage drop = current * resistance






13. - 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






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






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






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






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






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






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






20. 1. Ability of the material to absorb energy prior to fracture 2. Short term dynamic stressing - Car collisions - Bullets - Athletic equipment 3. This is different than toughness; energy necessary to push a crack (flaw) through a material 4. Useful in






21. 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






22. 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.






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






24. 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.






25. 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.






26. Specular: light reflecting off a mirror (average) - Diffuse: light reflecting off a white wall (local)






27. 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.






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






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






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






31. Because of ionic & covalent-type bonding.






32. 1. Electron motions 2. The spins on electrons - Net atomic magnetic moment: sum of moments from all electrons.






33. These materials are relatively unaffected by magnetic fields.






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






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






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






37. Materials change size when temperature is changed






38. Different orientation of cleavage planes in grains.






39. 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)






40. Cracks propagate along grain boundaries.






41. Light Amplification by Stimulated Emission of Radiation






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






43. 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






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






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






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






47. 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."






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






49. 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






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