Question detail
If a device has an efficiency of 80% and the total energy input is 2000 J, 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. 1600 J
- B. 1800 J
- C. 2000 J
- D. 1400 J
Answer
1600 J
Explanation
The correct option is "1600 J". 1600 J is right because it directly matches Energy transfers in a system: Use the term wasted energy to describe energy transferred in less useful ways.. 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
Misunderstanding Wasted Energy
Students often confuse wasted energy with energy that is simply lost, thinking it disappears rather than being transferred to less useful stores.
Clarify that wasted energy is energy that is transferred in ways that are not useful for the intended purpose, but it is still present in the system.
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