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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. Light Amplification by Stimulated Emission of Radiation






2. Diffuse image






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






4. 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.






5. Emitted light is in phase






6. There is always some statistical distribution of flaws or defects.






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






8. 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.






9. 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."






10. Because of ionic & covalent-type bonding.






11. Cracks propagate along grain boundaries.






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






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






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






15. 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)






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






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






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






19. 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






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






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






22. 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






23. Second phase particles with n > glass.






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






25. 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.






26. 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.






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






28. 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)






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






30. Sigma=ln(li/lo)






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






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






33. Occur when lots of dislocations move.






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






35. Measures Hardness 1. psia = 500 x HB 2. MPa = 3.45 x HB






36. 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.






37. 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






38. Ohms Law: voltage drop = current * resistance






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






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






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






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






43. 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.






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


45. 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






46. - 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






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






48. - 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






49. Stress concentration at a crack tips






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