HSSC-1 (Class-11) Solved Physics MCQs; Unit-10: Thermodynamics;  (New Book/KPK Text Board, Peshawar) With Verified Answers 


1. Assume we can change the equilibrium state of a system via two different processes. Assume that the initial and the final state are the same. Which of the quantities `\Δ_U`, ΔQ, ΔW, and ΔT must be the same for the two processes?




... Answer is B. Only ΔU and ΔT
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2. In any process the maximum amount of mechanical energy that can be converted to heat




... Answer is A. Depends upon the amount of friction
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3. In an isothermal change, internal energy




... Answer is D. remains constant
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4. A thermos bottle containing hot coffee is vigorously shaken. Consider coffee as system, then its temperature




... Answer is A. Increases
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5. Maximum work can be obtained in tie process called




... Answer is C. Isothermal
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6. A heat engine takes in 800 J of heat at 1000 K and exhausts 600 J of heat at 400 K. What the actual efficiency of this engine?




... Answer is A. 25%
Efficiency η% = 1 - `\ frac {QL}{QH}` x 100 = 1 - `\ frac {600}{800}`= 25%


7. If the temperature of the heat source is increased, the efficiency of a Carnot's engine :




... Answer is A. Increases
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8. Triple point of water is




... Answer is D. 273.16°K
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9. A real gas can be approximated to an ideal gas at




... Answer is A. Low density
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10. If the volume of the gas is to be increased by 4 times, then




... Answer is C. At constant T the pressure must be increased by four times
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11. In which of the systems listed below is the entropy decreasing?




... Answer is A. A gas is cooled.
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12. If the temperature of the source and sink of a Carnot engine having efficiency η are each decreased by 100K, then the efficiency η :




... Answer is C. increases.
Let T1 = 200 K and T2 = 400 K 👉 Efficiency η% = 1 - `\ frac {T2}{T1}` x 100 = 1 - `\ frac {200 K}{400 K}`= 50% 👉 When the temperature is decrease by 100 K 👉 Efficiency η% = 1 - `\ frac {T2 - 100 K}{T1 - 100 K}` x 100 = 1 - `\ frac {200 K - 100 K}{400 K - 100 K}`= 67%




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