An ideal heat engine absorbs 2,000 J of thermal energy from a high-temperature heat reservoir and discharges 1,400 J to a cold sink during each cycle. What is its thermal efficiency?
Answer and explanation
Correct answer: C. 30%
- Step 1: Work output: W = Q_H - Q_C = 2000 - 1400 = 600 J. Step 2. Thermal efficiency: Ī· = W / Q_H = 600 / 2000 = 0.30 = 30%. Answer: 30%. Why not the others: 70% is the waste heat fraction Q_C / Q_H; 40% and 25% are calculation errors.
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