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This quiz contains 12 questions from a mix of 1 subtopics.
What is the formula used to calculate efficiency?
efficiency = total energy input ÷ useful energy output
efficiency = total energy input - useful energy output
efficiency = useful energy output x total energy input
efficiency = useful energy output ÷ total energy input
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If a machine takes in 1,200 J of energy and converts it into 480 J of useful output energy, what is its efficiency?
20%
28%
60%
40%
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What is the theoretical limit for efficiency according to the laws of thermodynamics?
100%
90%
75%
50%
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If an electrical generator takes in 25,000 J and outputs 18,000 J of electricity, what is its efficiency?
82%
45%
28%
72%
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Why is higher efficiency generally desirable?
it lowers operating costs
it decreases harmful emissions
all of the above
it reduces resource usage
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What quantifies how well energy is converted to useful output rather than being wasted?
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What type of energy transformation always decreases efficiency?
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Give 3 reasons why higher efficiency is generally desirable.
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A light bulb uses 60 J of energy to produce 15 J of light energy. Calculate the efficiency of the light bulb.
75%
25%
40%
20%
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An engine consumes 1000 J of thermal energy and performs 300 J of mechanical work. What is the efficiency of the engine?
70%
50%
30%
25%
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A heater converts 2,000 J of electrical energy into 1,500 J of heat energy. What is its efficiency?
75%
25%
50%
85%
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A generator produces 500 J of electrical energy from 800 J of mechanical energy. Calculate the efficiency of the generator.
75%
37.5%
50%
62.5%
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