Exam 1 Practice Problems WITH Answers

# Three point charges are positioned on the x axis at

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53. Three point charges are positioned on the x -axis: at , at and at . What is the magnitude of the electrostatic force on the charge? ( ) a. 84 b. 12 c. 36 d. 50 e. 48 54. The Second Law of Thermodynamics states that Dr. Cyril Anoka’s Exam one Review

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55. What is the thermal e ffi ciency of a Carnot engine? 56. The coe ffi cient of performance of a heat pump is 57. Thermal e ffi ciency can be described mathematically as a. . b. . c. . d. . e. . 58. What is the change in entropy in J/K of 2.51 mol of an ideal gas due to a free expansion to 3.62 times its original volume? ( ) Dr. Cyril Anoka’s Exam one Review
59. What is the change in entropy in J/K of 0.356 kg of solid lead when it melts at 327°C if the latent heat of fusion of lead is 24.5 kJ/kg? 60. Ten kg of water at 0°C is mixed with ten kg of water at 100°C. The change in entropy in cal/K of the system is 61. A vessel containing 10 kg of water is left out where it evaporates. Assuming the temperature remains constant at 20°C, what is the change in entropy in kcal/K? (The latent heat of vaporization at 20°C is 585 cal/g.) a. 30 b. 10 c. 20 d. 40 e. 290 62. If n moles of an ideal gas are compressed isothermally from an initial volume to a final volume , the change in entropy is Dr. Cyril Anoka’s Exam one Review

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63. An engine is designed to obtain energy from the temperature gradient of the ocean. What is the thermodynamic e ffi ciency of such an engine if the temperature of the surface of the water is 59°F (15°C) and the temperature well below the surface is 41°F (5°C)? 64. The change in entropy of mass m of water having a mass m that is heated from an absolute temperature to is 65. A company that produces pulsed gas heaters claims its e ffi ciency is approximately 90%. If the engine operates between 250°C and 25°C, what percentage is its thermodynamic e ffi ciency? a. 83% b. 65% c. 43% d. 90% e. 56% 66. A gasoline engine absorbs 2500 J of heat and performs 500 J of mechanical work in each cycle. The amount of heat in J expelled in each cycle is 67. What is the maximum e ffi ciency of a heat engine operating between 500 K and 200 K? Dr. Cyril Anoka’s Exam one Review
68. In the formula for the maximum possible e ffi ciency of a heat engine, , the temperatures must be in 69. When a process occurs in an isolated system, the a. temperature increases. b. temperature decreases. c. entropy stays the same. d. entropy decreases. e. entropy increases. Dr. Cyril Anoka’s Exam one Review

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