If a device consumes 200 W and outputs 150 W of useful work, what is its efficiency?

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Study for the Ontario Power Generation (OPG) Orange 1 Test. Ace your exam with multiple choice questions and detailed explanations. Prepare confidently!

Multiple Choice

If a device consumes 200 W and outputs 150 W of useful work, what is its efficiency?

Explanation:
Efficiency is the ratio of useful output energy to the energy put in. Here, the device delivers 150 W of useful work from a 200 W input. So efficiency = 150 W / 200 W = 0.75, or 75%. That also means 50 W is lost as losses like heat or friction. The other percentages would require different amounts of useful output (e.g., 60% would need 120 W, 80% would need 160 W, 90% would need 180 W), which aren’t the case here.

Efficiency is the ratio of useful output energy to the energy put in. Here, the device delivers 150 W of useful work from a 200 W input. So efficiency = 150 W / 200 W = 0.75, or 75%. That also means 50 W is lost as losses like heat or friction. The other percentages would require different amounts of useful output (e.g., 60% would need 120 W, 80% would need 160 W, 90% would need 180 W), which aren’t the case here.

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