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






2. Cracks propagate along grain boundaries.






3. 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)






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






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






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






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






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






9. Second phase particles with n > glass.






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






11. - 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






12. 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






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






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






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






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






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






18. Light Amplification by Stimulated Emission of Radiation






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






20. 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






21. The ability of a material to absorb heat - Quantitatively: The energy required to produce a unit rise in temperature for one mole of a material.






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






23. Is analogous to toughness.






24. 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)






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






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






28. Stress concentration at a crack tips






29. Occur due to: restrained thermal expansion/contraction -temperature gradients that lead to differential dimensional changes sigma = Thermal Stress






30. Undergo little or no plastic deformation.






31. 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.






32. 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






33. 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






34. 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.






35. Occur when lots of dislocations move.






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






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






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






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






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






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






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






43. 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.






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






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






47. 1. Tc= critical temperature- if T>Tc not superconducting 2. Jc= critical current density - if J>Jc not superconducting 3. Hc= critical magnetic field - if H > Hc not superconducting






48. Different orientation of cleavage planes in grains.






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






50. 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






Can you answer 50 questions in 15 minutes?



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