Exam 1 - Practice Test PDF

Note: This practice test is provided as a study aid – it gives you a rough idea of the length of the exam, question distribution, and difficulty level. Individual students may find the actual exam to be harder or easier than the practice test. Fill out the top of your bubble sheet as demonstrated b...

Note: This practice test is provided as a study aid – it gives you a rough idea of the length of the exam, question distribution, and difficulty level. Individual students may find the actual exam to be harder or easier than the practice test. Fill out the top of your bubble sheet as demonstrated below. It is very important to correctly have your Name, GT Username, Version, and Section filled in! If you leave one of these out, 5 percentage points will be deducted from your final score. Your exam version is version A (Exam version is NOT the same as your assigned section: B, C, or E) Sign the Honor Statement: I commit to uphold the ideals of honor and integrity by refusing to betray the trust bestowed upon me as a member of the Georgia Tech community. Name: Date Signature: Once we begin, you will have the remainder of class time to complete the exam. You may remove the front equation sheet and you may write on the exam booklet. When you are finished, please hand in your exam to the TA and show your BuzzCard to confirm exam attendance. Good luck! EQUATIONS: 𝑑𝐶 𝐽 = −𝐷 𝐶 𝐴 = 𝑘 𝜀0 𝑑𝑥 𝑡 𝐸𝑎 𝑙 𝐷 = 𝐷𝑜 exp (− ) 𝑅= 𝜌 𝑘𝑏𝑇 𝐴 Λ 𝑅+𝐴+𝑇 =1 𝐷𝑡ℎ ∝ Δ𝐿 = 𝐿𝑖𝛼Δ𝑇 𝐶𝑝 CONVERSIONS CONSTANTS giga - 109 ε = 10-11 F/m 0 mega - 10 6 centi - 10-2 kb = 10-4 eV/K milli - 10-3 micro (μ) - 10-6 nano - 10-9 pico - 10-12 PERIODIC TABLE 1 Which of the following best describes the main theme of the materials science and engineering discipline? (A) MSE seeks to understand and apply the inter-relationships between how materials are processed, their structure, and their resultant properties. (B) MSE seeks to understand how to design the shape and size of material to optimize performance. (C) MSE seeks to make the strongest, most robust materials known to man. (D) MSE seeks to measure material constants as precisely as possible without trying to understand the underlying structure that affects these constants. (E) MSE does not have a central paradigm, it’s just a hodgepodge of ideas I need to memorize so I can pass this course. 2 Which of the following is a performance parameter (NOT a materials constant): (A) Heat Capacity (B) Reflectivity (C) Conductivity (D) Capacitance (E) Both C & D 3 Which of the following is an example of a thermal property of a material? (A) Ductility (B) Piezoelectricity (C) Resilience (D) Heat capacity (E) Both C & D 4 If you wanted to quantitatively assess the visible color of a dyed polymer sheet, which of the following instrument(s) might you use: (A) Tensile Tester (B) Hardness Tester (C) UV/Vis Spectrometer (D) B & C (E) None of these 5 The refractive index of a material would be classified as: (A) A chemical property (B) A mechanical property (C) An optical property (D) Both A & C (E) Both B & C 6 In your new engineering job, you are asked to evaluate two glass-polymer composite materials for a structural (weight-bearing) application. One composite uses glass shaped as sheets while the other composite uses glass shaped as fibers. Both composites are composed of 50% glass and 50% polymer. Without seeing the specification sheet, would you be willing to believe the following statement from the vendor selling you the composite: “Both materials will have nearly the same mechanical strength and toughness because they both have the same composition.” (A) Yes, this sounds believable. (B) No, this sounds suspicious. 7 Piezoelectricity would be classified as: (A) A mechanical property (B) An electrical property (C) A chemical property (D) Both A and B (E) Both A and C 8 You are out on a hike and find a cool rock. When your cool new rock is scratched with calcite, nothing happens to your rock. When your rock is scratched with quartz, quartz leaves a scratch mark on your rock. Which of the following MUST be true about your rock if it is used to scratch the following minerals: (A) Your rock will leave a scratch mark on gypsum. (B) Your rock will leave a scratch mark on apatite. (C) Your rock will leave a scratch mark on ruby. (D) A & B only. (E) A, B, and C. 9 In the plot shown above, the yield strength (y) is notated by: (A) Point A (B) Point B (C) Point C (D) Point D 10 You are hired to design a diving board (spring board) for a swimming pool. The board material should flex but neither break nor permanently deform. To get this performance, you should select a material with… (A) …a low yield strength but high fracture toughness. (B) …a low yield strength and low fracture toughness. (C) …an extremely high elastic modulus and a high yield strength. (D) …a moderate elastic modulus and a low yield strength. (E) …a moderate elastic modulus but a high yield strength. 11 Which of these drawings BEST depicts the toughness of a material? 12 At your new job, you build gas distribution networks from ¼” stainless steel tubing. You use a manual tube bender to make angles in the tubing (see picture). When bending the metal tubing to create a permanent 90° angle, you should: (A) Initially bend tube slightly more than 90° to account for the metal’s elastic recovery (B) Initially bend tube slightly less than 90° to account for the metal’s elastic recovery (C) Initially bend the tube to exactly 90° -- it’s best to be precise the first time! (D) Initially bend tube slightly more than 90° to account for the metal’s plastic response (E) Initially bend tube slightly less than 90° to account for the metal’s plastic response 13 Eyeglass lenses are often made from polymers because they are lightweight. However, these polymer lenses are easy to scratch. What would you recommend doing to improve the scratch resistance of these polymeric lenses? (A) Apply a transparent ceramic coating with high hardness to the polymer surface. (B) Galvanize the polymer with an optically reflective zinc metal coating. (C) Include additives in the polymer that increase the refractive index. (D) Include additives in the polymer that increase the dielectric breakdown. (E) Make a composite with glass fibers embedded inside of the polymer lens. 14 This material property measurement tool impresses a small diamond tip into the surface of a material to a fixed load value. The size of the indent created is then measured to quantify a specific property. Which property are you measuring? (A picture of such an indent is shown in the image to the right.) (A) Optical reflectivity (B) Piezoelectric Coefficient (C) Electrochemical Potential (D) Mechanical Hardness (E) Dielectric Constant 15 Why are foam panels used to absorb sound in recording studios? (A) Foam has a similar acoustic impedance to air, allowing the sound to enter the foam. Once inside the foam, the sound waves are strongly absorbed by the foam. (B) Foam’s large acoustic impedance mismatch with air allows the sound to enter the foam. Once inside the foam, the sound waves are strongly absorbed by the foam. (C) Foam has a similar acoustic impedance to air, allowing the sound to enter the foam. Once inside the foam, sound waves mostly transmit through the foam. (D) Foam’s large acoustic impedance mismatch with air allows the sound to enter the foam. Once inside the foam, sound waves mostly transmit through the foam. (E) Foam actually doesn’t have good acoustic properties; it’s just cheaper cheaper than metals or ceramics which would otherwise be better choices. 16 The “mechanical stiffness” of a material is equivalent to the material’s: (A) Elastic Modulus (B) Yield Strength (C) Ultimate Tensile Strength (D) Fracture Toughness (E) Modulus of Resilience 17 You are asked to design a skillet (pan) for cooking. The key requirement is that the skillet reaches the same temperature as the heat source (oven burner) as quickly as possible. Based on this requirement, which of the following materials would you select? (A) Material A: Thermal conductivity = 8 W/m-K, Heat Capacity = 2 J/mol-K (B) Material B: Thermal conductivity = 10 W/m-K, Heat Capacity = 2 J/mol-K (C) Material C: Thermal conductivity = 8 W/m-K, Heat Capacity = 4 J/mol-K (D) Material D: Thermal conductivity = 12 W/m-K, Heat Capacity = 3 J/mol-K (E) Material E: Thermal conductivity = 4 W/m-K, Heat Capacity = 8 J/mol-K 18 Consider heating 1 cm3 blocks of aluminum, zinc, and silver to 200°C. These heated blocks are then dropped into separate containers each filled with 100 mL of water. If each water container is initially at room temperature, which water bath will reach the highest temperature after dropping in the metal blocks? Material Heat Capacity Heat Capacity Thermal Conductivity (J/g K) (J/cm3 K) (W/m K) Aluminum 0.897 2.42 205 Zinc 0.387 2.76 116 Silver 0.233 2.44 406 (A) All of the water baths will reach the same temperature. (B) The water bath cooling the aluminum block will reach the highest temperature. (C) The water bath cooling the zinc block will reach the highest temperature. (D) The water bath cooling the silver block will reach the highest temperature. (E) Insufficient information is provided to make a prediction. 19 You are asked to help design a bimetallic temperature sensor. You are given five metal alloys to work with; their thermal expansion coefficients are listed below. Assuming the elastic properties for each alloy are identical, which combination of alloys would give you the largest temperature-sensitive deflection for your sensor design? Thermal Expansion Coefficients of Alloys Alloy 1: 15 m/m-K Alloy 2: 10 m/m-K Alloy 3: 8 m/m-K Alloy 4: 5 m/m-K (A) Alloy 1 and Alloy 2 (B) Alloy 3 and Alloy 4 (C) Alloy 1 and Alloy 4 (D) Alloy 2 and Alloy 3 (E) Any combination will work equally well 20 How does a bimetallic strip act as a temperature-activated mechanical switch in a thermostat? (A) The thermal expansion matching of the two metals prevents delamination with changes in temperature. (B) The thermal expansion mismatch of the two metals causes mechanical deflection with changes in temperature. (C) The heat capacity mismatch of the two metals causes mechanical deflection with changes in temperature. (D) The thermal expansion matching of the two metals prevents mechanical deflection with changes in temperature. (E) The average thermomechanical coefficient of the two materials is large enough to cause a mechanical deflection with changes in temperature. 21 If you join two materials with different thermal expansion coefficients and then heat them up, which material will be in tension? (A) The material with a higher CTE, because it expands more, and that expansion causes internal tension. (B) The material with a higher CTE, because it gets hotter, and heat energy causes internal tension. (C) The material with a lower CTE, because it expands less, and feels a tensile pull from the other material. (D) The material with a lower CTE, because it expands more, and feels a tensile pull from the other material. (E) Both materials are equally in tension because they are joined. 22 What properties and what material class would make for a good thermal barrier coating? (A) Ceramics: they have very high service temperatures and relatively high thermal conductivity. (B) Ceramics: they have very high service temperatures and relatively low thermal conductivity. (C) Metals: they have relatively high service temperatures and very high thermal conductivity. (D) Metals: they have high thermal conductivity and relatively high heat capacity. (E) Polymers: they have the lowest thermal conductivity and relatively high heat capacity. 23 A good dielectric material designed for use in a capacitor should: (A) Have a high dielectric constant and be a good electrical conductor (B) Have a high dielectric constant and be a good electrical insulator (C) Have a low dielectric constant and be a good electrical conductor (D) Have a low dielectric constant and be a good electrical insulator 24 Consider a copper rod that is 3.14 meters long, 2 cm in diameter, and has an electrical resistivity of 2x10-6 ohm-cm. If the rod is cut in half what is the electrical resistivity of each piece? (A) 1x10-6 ohm-cm (B) 2x10-6 ohm-cm (C) 1x10-4 ohm-cm (D) 2x10-4 ohm-cm (E) Not enough information to provide an exact answer. 25 The figure at right plots the hysteresis curves (magnetization [M] versus magnetic field [H]) for three different materials (A, B, and C). Consider if you had to choose a material for an application that required a permanent magnet. Which of these materials would give the largest permanent magnetization? (A) Material A (B) Material B (C) Material C (D) Materials B & C would equivalent permanent magnetization. (E) All three materials have equivalent permanent magnetization. 26 True/False: Electrical conductivity (σ) is the inverse of electrical resistivity (ρ) (A) True (B) False 27 Which of the following best describes the electronic behavior in a semiconductor? (A) The electrons spend 50% of the time in bound (valence) state and 50% of the time in a conducting state. (B) The electrons can change from a bound (valence) state to a conducting state, but once a high enough voltage is applied for it to conduct, it can’t switch back. (C) The electrons can switch back and forth between conducting or bound (valence) states, depending on applied voltage. (D) The energy gap between bound (valence) and conducting states in a semiconductor is negligibly small and does not affect the material properties. (E) The energy gap between bound (valence) and conducting states in a semiconductor is higher than in both metals and insulators, giving semiconductors unique properties. 28 When in contact with a horseshoe magnet, paper clips can become magnetized and create a chain. This paper clip chain will fall apart when the horseshoe magnet is removed. Which of the following best describes this phenomenon? (A) The horseshoe magnet and the paper clips are both hard magnetic materials, but the horseshoe magnet has a higher saturation magnetization than the paper clips. (B) The horseshoe magnet and the paper clips are both hard magnetic materials, but the horseshoe magnet has a higher coercive field than the paper clips. (C) The horseshoe magnet and the paper clips are both soft magnetic materials, but the horseshoe magnet has a lower remanent magnetization than the paper clips. (D) The horseshoe magnet is a hard magnet, while the paper clips are made of a soft magnetic material. (E) The horseshoe magnet is a soft magnet, while the paper clips are made of a hard magnetic material. 29 For a 1-inch-thick sheet of copper, the optical reflectivity is measured to be 75% at a wavelength of 500 nm. What is the optical absorptivity of this copper sheet at a wavelength of 500 nm? (A) 0% (B) 25% (C) 75% (D) 100% (E) Not enough information is given to solve this problem. 30 Randomly polarized light reflected off of a specular (smooth) surface… (A) …remains randomly polarized. (B) …obtains a preferential polarization. (C) …generates a “blurry” reflected image. (D) Both A & C (E) Both B & C 31 The brilliance of a diamond is qualitatively defined by how much it sparkles. Scientifically, this means that when light enters the diamond, it is diverted into many different directions based on color. The light exiting the diamond and viewed by our eyes is separated both by its direction of travel (spatially) and by its color (wavelength). These multiple, colored beams of light give a diamond its sparkle. Which of the following parameters must engineers consider when designing the sparkle of a diamond? (A) The optical dispersion of the diamond (B) The refractive index of the diamond (C) The shape of the diamond (D) Both A & B (E) A, B, and C 32 What happens when light passes through a vertically-oriented linear polarizer? (A) The polarizer will only let through light that matches its orientation, which will always reduce the intensity by 50%. (B) The polarizer will only let through light that matches its orientation, which will reduce the intensity by 50% only if the light was randomly polarized. (C) The polarizer will only let through light that matches its orientation, which will reduce the intensity by an unknown percentage if the light was randomly polarized; we need more information to determine the percentage. (D) The polarizer will preferentially let through light of lower wavelengths. (E) The polarizer will preferentially let through light of higher wavelengths. 33 After a hot shower, the mirror in your bathroom often becomes foggy and the reflected image looks “distorted” or “blurred”. This blurred image is the result of small (micron- sized) water droplets condensing on the mirror’s surface. How do you explain the change in the optical performance of the mirror? (A) The water droplets diffract the light. (B) The water droplets create a rough surface that diffusely scatters the light. (C) The water droplets create a rough surface that specularly scatters the light. (D) The water droplets polarize the light, altering the reflectivity. (E) The water droplets polarize the light, altering the absorptivity.  Standard Reduction Potential Metal Electrochemical Reaction (V) Gold (Au) Au+ + e- ➔ Au +1.52 Water (H2O) 2OH- ➔ H2O + ½ O2 + 2 e- +0.40 Copper (Cu) Cu2+ + 2 e- ➔ Cu 0.34 Molybdenum (Mo) Mo4+ + 4 e- ➔ Mo -0.15 Iron (Fe) Fe2+ + 2 e- ➔ Fe -0.44 Zinc (Zn) Zn2+ + 2 e- ➔ Zn -0.76 Niobium (Nb) Nb3+ + 3 e- ➔ Nb -1.09 Vanadium (V) V2+ + 2 e- ➔ V -1.13 Aluminum (Al) Al3+ + 3 e- ➔ Al -1.63 Neodymium (Nd) Nd2+ + 2 e- ➔ Nd -2.1 Lithium (Li) Li+ + 1 e- ➔ Li -3.04 34 If you want to cathodically protect a vanadium component from corrosion, which of the following metals might you select as the sacrificial anode? (A) Niobium (B) Neodymium (C) Iron (D) Both A & B would work (E) None of these would work 35 Which of the following scenarios is most likely to lead to severe galvanic corrosion of at least one component. (A) A plastic sign bolted to an iron post with an iron nut and bolt intended for use in the ocean. (B) A copper sheet bolted to a copper post with an iron nut and bolt intended for use in the ocean. (C) An iron sheet bolted to an iron post with an iron nut and bolt intended for use in the ocean. (D) An anodized sheet of aluminum bolted to an anodized aluminum post with an iron nut and bolt intended for use in the home. (E) A copper sheet bolted to a copper post with an iron nut and bolt intended for use in the home. 36 A galvanized steel component is protected from corrosion because: (A) The coating layer forms a protective barrier that prevents corrosion of the steel. (B) The coating layer creates cathodic protection of the steel. (C) The coating layer creates anodic protection of the steel. (D) Both A & B (E) Both B & C 37 Anodized aluminum is aluminum that is… (A) …covered in a zinc coating that protects the aluminum from corrosion by two mechanisms: (1) physically blocking oxidizing species from reaching the aluminum and (2) via cathodic protection. (B) …covered in a zinc coating that protects the aluminum from corrosion by two mechanisms: (1) physically blocking oxidizing species from reaching the aluminum and (2) via anodic protection. (C) …electrochemically oxidized to form a self-oxide with a controlled thickness that physically blocks oxidizing species from reaching the aluminum. (D) …electrochemically oxidized to form a self-oxide with a controlled thickness that cathodically protects the aluminum from corroding. (E) …electrochemically oxidized to form a self-oxide with a controlled thickness that anodically protects the aluminum from corroding. 38 How might you go about designing a polymer component that is chemically resistant to dissolution in the organic solvent acetone? (A) Use a Durability Table to select the proper polymer. (B) Apply a ceramic coating to the surface of the polymer. (C) Use cathodic protection. (D) Both A & B (E) A, B, & C 39 Rubies are a red gemstone that are very hard and have chemical formula Al2O3, deriving their red color from small amounts of chromium impurities. How would you classify this material: (A) Polymer (B) Ceramic (C) Metal (D) Elastomer (E) A & D 40 Which of the following material classes is defined by having extremely high strain at yield (up to 400%): (A) Metal alloy (B) Intermetallic (C) Elastomer (D) Semicrystalline polymer (E) Semiconductor 41 Polymers have relatively lower density than other materials because: (A) The elements they are composed of are typically less dense than those in metals and ceramics. (B) They are arranged like a mess of spaghetti, which is not packed very densely. (C) Polymers have very few atoms per molecule, which makes them less dense. (D) Both A &B (E) A, B & C 42 Textiles (i.e., the clothes we wear) are usually made out of: (A) Ceramics (B) Metals (C) Polymers (D) Intermetallics (E) Glasses 43 Gallium arsenide (GaAs) is best classified as a: (A) Polymer (B) Ceramic-Metal Composite (Cermet) (C) II-VI Semiconductor (D) III-V Semiconductor (E) Glass 44 You need to choose a material to create a jar to store a strong acid. Your best choice would probably be: (A) A ceramic material like glass, because ceramics tend to be the most resistant to corrosion and chemical attack by strong acids. (B) A pure elemental metal like copper, because the high purity correlates with chemical inertness. (C) A polymer material like high density polyethylene, because polymers only dissolve in organic solvents. (D) A metal that has been painted with a polymer coating to get the composite benefits of both metal and polymer resistance to chemical attack. (E) Any of these materials could be an equally good choice if you just make the jar thick enough. 45 Stress-strain curves for materials A, B, and C are shown above. Which material has the largest elastic modulus? (A) Material A (B) Material B (C) Material C (D) A and B both have the same elastic modulus (E) Elastic moduli cannot be compared using a stress-strain curve ~End of Exam 1~