quiz lesson 3

# The energy input of a system is 91 calories

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Unformatted text preview: rcentage? Correct A ) 26.2 Energy efficiency = Useful energy output / Total energy input Useful energy output = 13 - 8 - 1.6 = 3.4 million Joules Efficiency of the boiler = 3.4 / 13 x 100 = 26.15% Electricity can be generated from fossil fuels. Correct A ) TRUE Renewable and non renewable energy sources can be converted to electricity and heat. Approximately what percentage of electricity does an incandescent light bulb convert into visible light? Correct A ) 5 Most of the electrical energy is lost in the form of heat in an incandescent light bulb, only 5% is converted into visible light The flame temperature in an automobile engine is 1000oC, and the exhaust is emitted at 197oC. What is the maximum possible efficiency of this engine in percentage? Correct A ) 63.1 Carnot's Efficiency = (1 - (Tcold / Thot)) x 100 Thot = 1000 + 273 = 1273 K Tcold = 197 + 273 = 470 K Carnot's Efficiency = (1 - (470 / 1273)) x 100 = 63.07% Which one of the following devices is least energy efficient? Correct C ) Light bulb Typically a power plant has an efficiency of 35%, and an electric motor has an efficiency of 90% An incandescent electric bulb has an efficiency of 5% and fluorescent light bulb has an efficiency of about 20% From a car, useful energy output is __________. Correct C ) Mechanical Motion of the car (mechanical energy) is the useful energy output from a car What is the form of useful energy output in the case of a lawn mower? Correct A ) Mechanical A lawn mower converts chemical energy from the burning of fuel into mechanical energy (rotation of blades). What is the form of useful energy output in the case of a computer screen? Correct A ) Radiation A computer screen converts electrical energy into radiation (the pictures and text that we see on the computer screen). What is the most common by product of energy conversion processes? Correct B ) Heat Most energy conversion processes produce heat as a by product 18 million Joules of chemical energy are supplied to a boiler in a power plant....
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## This note was uploaded on 09/24/2013 for the course EGEE 102 taught by Professor Pisupati,sarmave during the Spring '07 term at Penn State.

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