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Engineering Materials

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
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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. 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.






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






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






4. 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.






5. Because of ionic & covalent-type bonding.






6. - 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






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






8. 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.






9. Ohms Law: voltage drop = current * resistance






10. 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






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






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






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






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






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






16. 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






17. Different orientation of cleavage planes in grains.






18. 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






19. 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.






20. 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.






21. High toughness; material resists crack propagation.






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






23. 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






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






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






26. 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.






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






28. Occur when lots of dislocations move.






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






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

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






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






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






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






35. Light Amplification by Stimulated Emission of Radiation






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






37. 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."






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






39. 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






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






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






42. Second phase particles with n > glass.






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






44. 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.






45. 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






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






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






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






49. 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






50. Emitted light is in phase