# If You Rest, You Rust

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PU11 Physics Question Bank – Heat & Thermodynamics One mark questions 1. In a Carnot engine, the temperature of the sink is 27 C and that of the source is 327 C . What is the efficiency of the Carnot engine? Ans:   1  2. T2 273  27 300 1  1  1  T1 273  327 600 2 How is the efficiency of a Carnot engine affected by the nature of the working substance? Ans: The efficiency is independent of the nature of the working substance. 3. Give one example of a heat pump. Ans: Refrigerator is an example of a heat pump. 4. What is a heat pump? Ans: A heat pump is a device which uses mechanical wok to remove heat. 5. It is possible to heat a room by means of a refrigerator. Is this method most advantageous from ‘energy’ point of view? Ans: From energy point of view, the proposition is not sensible. 6. State second law of thermodynamics. Ans: dQ  Tds ds  dQ T dS  change in entrophy Change in entropy in equal to the ratio of heat to the absolute temperature. 7. Refrigerator transfers heat from a cold body to a hot body. Does this not violate the second law of thermodynamics? Ans: No. This is because external work is being performed. 8. The door of an operating refrigerator is kept open in a closed room. Will it make the room warm or cool? Ans: The room will be slightly warmed. 9. What is a heat engine? Ans: An engine which convert heat energy into mechanical work Ex: car note engines. 10. Define Quasi-static process. Ans: If a substance is under constant pressure from all sides. Then the substance is said to be in Quasi – state. 11. Can we increase the coefficient of performance of a refrigerator by increasing the amount of working substance? PU11 Physics Question Bank – Heat & Thermodynamics Ans: No 12. Can the Carnot engine be realised in actual practice? Ans: No. It is an ideal heat engine. 13. What type of