The efficiency of a device is the?

A. difference between the useful work output and the total input energy

B. ratio of the useful work output to the total input energy 

C. ratio of the total input energy to the useful work output

D. sum the waste energy and the useful work output

2 Answers

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  • oubaas
    Lv 7
    4 weeks ago

    B. ratio of the useful work output to the total input energy 

  • 4 weeks ago

    B. If you put 100 kJ into a machine but only get 80 kJ back, then the machine is 80% efficient.

    As a rule, efficiencies are always between 0 and 1 because an efficiency greater than 1 implies you get more energy out than you put in, which contradicts the First Law of Thermodynamics. Efficiencies of 1 are also pretty much impossible due to losses to heat, friction, et cetera.

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