Question detail
If a device has a useful energy output of 40 J and a total energy input of 100 J, what is its efficiency as a percentage?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Conservation and dissipation of energy
Question
- A. 40%
- B. A distractor that confuses Efficiency with a different Energy idea
- C. A distractor that ignores express efficiency as a percentage
- D. A distractor that uses the wrong unit or relationship for this question
Answer
40%
Explanation
The correct option is "40%". 40% is right because it answers the Efficiency objective: Express efficiency as a percentage.. The distractors are incorrect because they either use the wrong Physics quantity, confuse an energy store with a transfer, or ignore the wording of this question.
Common mistake
Confusing Efficiency Representation
Students often express efficiency as a decimal instead of a percentage, leading to incorrect answers.
To express efficiency as a percentage, multiply the decimal value by 100.
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