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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. 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






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






3. Diffuse image






4. Undergo extensive plastic deformation prior to failure.






5. 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.






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






7. 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






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






9. Ohms Law: voltage drop = current * resistance






10. 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






11. Emitted light is in phase






12. Occur when lots of dislocations move.






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






14. 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






15. - Metals that exhibit high ductility - exhibit high toughness. Ceramics are very strong - but have low ductility and low toughness - Polymers are very ductile but are not generally very strong in shear (compared to metals and ceramics). They have low






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






17. (sigma)=K(sigma)^n . K = strength coefficient - n = work hardening rate or strain hardening exponent. Large n value increases strength and hardness.






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






19. 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






20. 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)






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






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






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






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






25. - 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






26. 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.






27. 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






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






29. 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






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






31. These materials are relatively unaffected by magnetic fields.






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






33. Is analogous to toughness.






34. 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






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






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






37. 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.






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






39. 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.






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






41. High toughness; material resists crack propagation.






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






43. 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.






44. 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."






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






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






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






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






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






50. Light Amplification by Stimulated Emission of Radiation