Question detail
If a device has a total energy input of 5000 J and an efficiency of 0.85, what is the useful energy output?
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. 4250 J
- B. 4000 J
- C. 4500 J
- D. 3500 J
Answer
4250 J
Explanation
The correct option is "4250 J". 4250 J is right because it directly matches Efficiency: Calculate efficiency using useful energy output divided by total energy input.. The other options are less suitable because they change the required Physics relationship, confuse the relevant energy store or use a distractor that does not answer the question.
Common mistake
Confusing Efficiency Calculation
Students often confuse the formula for efficiency by using total energy output instead of useful energy output.
Remember to use the formula: efficiency = useful energy output / total energy input.
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