Test your basic knowledge |

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. 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.






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






3. Is analogous to toughness.






4. 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






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






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






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






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






9. 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






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






11. Occur when lots of dislocations move.






12. 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.






13. Second phase particles with n > glass.






14. 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






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






16. 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






17. 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.






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






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






20. 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.






21. 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






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






23. 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.






24. High toughness; material resists crack propagation.






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






26. 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)






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






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






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






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






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






32. 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






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






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






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






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






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






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






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






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






42. - 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






43. - 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






44. 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






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






46. 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.






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






48. 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.






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






50. 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