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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. 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






2. Undergo little or no plastic deformation.






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






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






5. High toughness; material resists crack propagation.






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






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






8. 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






9. Ohms Law: voltage drop = current * resistance






10. 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.






11. Sigma=ln(li/lo)






12. 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






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






14. 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






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






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






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






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






19. 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.






20. 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






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






22. Different orientation of cleavage planes in grains.






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






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






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

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






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






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






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

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






31. Is analogous to toughness.






32. Light Amplification by Stimulated Emission of Radiation






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






34. These materials are relatively unaffected by magnetic fields.






35. 1. Impose a compressive surface stress (to suppress surface cracks from growing) - Method 1: shot peening - Method 2: carburizing 2.Remove stress concentrators.






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






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






38. 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.






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






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






41. 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






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






43. 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)






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






45. With Increasing temperature - the saturation magnetization diminishes gradually and then abruptly drops to zero at Curie Temperature - Tc.






46. 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






47. They are used to assess properties of ceramics & glasses.






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






49. Occur when lots of dislocations move.






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