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Unformatted text preview: step efficiencies apply to the use of gasoline in a car: Crude production: 91%, Transportation 93%, Refining 93%, Distribution of gasoline 96%, Engine efficiency 28.8%. What is the overall efficiency of the process in percentage? Correct A ) 21.8 Overall Efficiency = 0.91 x 0.93 x 0.93 x 0.96 x 0.288 x 100 = 21.76% The flame temperature in an automobile engine is 1010oC, and the exhaust is emitted at 164oC. What is the maximum possible efficiency of this engine in percentage? Correct A ) 65.9 Carnot's Efficiency = (1  (Tcold / Thot)) x 100 Thot = 1010 + 273 = 1283 K Tcold = 164 + 273 = 437 K Carnot's Efficiency = (1  (437 / 1283)) x 100 = 65.93% A turbine is the most efficient component in a power plant. Correct B ) FALSE Turbine, being a heat engine, is the least efficient component The useful output from a heat engine is 249 cal. The energy that is wasted is 5675 J? What is the Carnot efficiency (maximum efficiency) of the engine? Correct B ) 15.56% Efficiency = ((useful energy output) / (useful energy output + waste energy output))*100. Note: Use units consistently. 1 Cal = 4.2 J Efficiency = (249 x 4.2) / [(249 x 4.2) + 5675] = 0.1556 = 15.56% 19 million Joules of chemical energy are supplied to a boiler in a power plant. 5 x 10^6 Joules of energy are lost through unburnt fuel. The boiler radiates 1.1 million Joules to the atmosphere. What is the efficiency of the boiler in percentage? Correct A ) 67.9 Energy efficiency = Useful energy output / Total energy input Useful energy output = 19  5  1.1 = 12.9 million Joules Efficiency of the boiler = 12.9 / 19 x 100 = 67.89% In a fossil fuel power plant(OVERALL) what type of energy (from fuel) is converted to electrical energy? Correct A ) Chemical In a power plant, fuel is burnt (chemical energy) to produce electricity with several intermediate steps. The flame temperature in an automobile engine is 1071oC, and the exhaust is emitted at 187oC. What is the maximum possible efficiency of this engine in percentage? Correct A ) 65.8 Carnot's Efficiency = (1  (Tcold / Thot)...
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 Spring '07
 PISUPATI,SARMAVE

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