Question detail
A machine has a useful power output of 1500 W and a total power input of 2000 W. Calculate the efficiency of the machine.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Conservation and dissipation of energy
Question
A machine has a useful power output of 1500 W and a total power input of 2000 W. Calculate the efficiency of the machine.
Answer
0.75 or 75%
Explanation
This answer stays anchored to Efficiency and uses the approved objective: Calculate efficiency using useful power output divided by total power input..
Common mistake
Confusing power with energy in efficiency calculations
Students often use total energy input instead of total power input when calculating efficiency for a device that operates over a period of time, leading to incorrect efficiency values.
Remind students that efficiency = useful power output ÷ total power input. Use power (W) values, not energy (J), and ensure both numerator and denominator refer to the same time interval.
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