Heat Engines Carnot & Refrigerator — Practice Questions
Free NEET Physics multiple-choice questions on Heat Engines Carnot & Refrigerator. Attempt each question and reveal the answer with a full explanation.
A Carnot engine operates between a source at 500 K and a sink at 300 K . If it absorbs 1000 J of heat from the source, how much heat is rejected to the sink? 600 J 400 J 500 J 200 J A refrigerator has a coefficient of performance (COP) of 5 . If the temperature inside the freezer is -20 C , the temperature of the surroundings to which it rejects heat is: 30.6 C 20 C 41 C 50 C A heat engine rejects 600 J of heat to the sink and has an efficiency of 40 % . The heat absorbed from the source is: 1000 J 1500 J 400 J 240 J A refrigerator's coefficient of performance (COP) is 4. If it extracts 200 J of heat from the cold reservoir, the work done on the system is: 50 J 800 J 250 J 150 J A refrigerator works between 4 C and 30 C . It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is ( 1 cal = 4.2 Joules ): 236.5 W 2.365 W 23.65 W 2365 W An engine has an efficiency of 1/6 . When the temperature of the sink is reduced by 62 C , its efficiency is doubled. The temperatures of the source and the sink are: 99 C, 37 C 124 C, 62 C 62 C, 31 C 37 C, 99 C A gas expands from 2 L to 6 L against a constant external pressure of 5 atm . The work done by the gas is used to heat 100 g of water. If the specific heat of water is 4.18 J g -1 K -1 , the rise in temperature is ( 1 L atm = 101.3 J ): 4.85 K 2.42 K 9.70 K 1.21 K A Carnot engine's efficiency is 50 % when the source temperature is T 1 and the sink is T 2 . If the sink temperature is reduced by 50 K , the efficiency becomes 60 % . The value of T 1 is: 500 K 400 K 600 K 300 K A Carnot engine has an efficiency of 25 % . If the temperature of the sink is reduced by 50 K , the efficiency increases to 33.33 % . The initial temperature of the source is: 600 K 450 K 300 K 750 K Two Carnot engines A and B are operated in series. Engine A receives heat at 900 K and rejects it to a reservoir at temperature T . Engine B receives the heat rejected by A and rejects it to a sink at 400 K . If the efficiencies of both engines are equal, T is: 600 K 650 K 500 K 700 K A refrigerator has a coefficient of performance of 3 . If it extracts 120 J of heat from the cold reservoir, how much work must be done on the system? 40 J 360 J 120 J 30 J An ideal heat engine working between T 1 and T 2 has an efficiency . If both temperatures are doubled, the new efficiency will be: 2 /2 1 - 2 The efficiency of a Carnot engine operating between 400 K and 800 K is: 0.5 0.75 0.25 0.6 In a Carnot engine, the temperature of the source is 600 K and the sink is 300 K . If the engine performs 500 J of work per cycle, the heat absorbed from the source is: 1000 J 500 J 250 J 1500 J The coefficient of performance ( COP ) of a refrigerator working between temperatures T 1 (source) and T 2 (sink) is given by: T 2 / (T 1 - T 2) T 1 / (T 1 - T 2) (T 1 - T 2) / T 2 (T 1 - T 2) / T 1 The efficiency of an ideal heat engine working between the freezing point and boiling point of water is: 26.8 % 20 % 6.25 % 12.5 % In a Carnot engine, if the temperature of the source is increased while keeping the sink temperature constant, the efficiency will: Increase Decrease Remain the same Initially increase then decrease A Carnot engine having an efficiency of = 1/10 as a heat engine, is used as a refrigerator. If the work done on the system is 10 J , the amount of energy absorbed from the reservoir at lower temperature is: 90 J 99 J 100 J 1 J