Same chapter3 marksDifficulty: Medium
A Carnot engine works between 500 K and 300 K. Find its efficiency.
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3 marksDifficulty: Medium
Why can the efficiency of a heat engine never be 100%?
Original Khojo Papers practice question — not from a past board paper.
Answer
A heat engine must reject some heat to a sink at a lower temperature to complete its cycle; only the difference between the heat taken in and the heat rejected is converted into work. The Kelvin-Planck statement of the second law says that a process whose sole result is the complete conversion of heat into work is impossible.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
The Carnot efficiency 1 − T2/T1 would be 1 only if the sink were at absolute zero.
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