MDCAT XII Physics 2nd Law Of Thermodynamics Online Test-2

Instructions for MDCAT XII Physics 1st Law Of Thermodynamics Online Test-2:

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Test Details:

Subject: Physics
Class: 2nd year or 12
Chapter Name: 2nd Law Of Thermodynamics
Test: MDCAT 2025
Book: Sindh Textbook
Total No. Of MCQS: 50 MCQS
Time Allowed: 50 Minutes
Price: Free

Created on April 16, 2025 By

medicoengineer.com

MDCAT XII Physics 2nd Law of Thermodynamics Online Test-2

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NameEmailPhone Number

1 / 50

1. Q/T₁ is equal to:

a) Decrease in entropy of the reservoir at T₁

b) Increase in entropy of the reservoir at T₁

c) Increase or decrease in entropy of the reservoir at T₁

d) None of these

2 / 50

2. A Carnot engine is:

a) A reversible engine

b) An irreversible engine

c) Both reversible and irreversible

d) Can't be determined

3 / 50

3. Efficiency of a Carnot engine working between 80.33°F and 260.33°F is:

a) 0.69

b) 0.7

c) 0.25

d) 0.3

4 / 50

4. In one complete Carnot cycle, entropy:

a) Increases

b) Decreases

c) May increase or decrease

d) Remains constant

5 / 50

5. A Carnot engine takes in 500 J of heat, the high-temperature reservoir is at 500 K, and it gives up 200 J of heat. How much mechanical work is done by the engine during this cycle?

a) 200 J

b) 300 J

c) 400 J

d) 500 J

6 / 50

6. During which processes of the Carnot engine is useful work extracted?

a) Process 1 and 2

b) Process 3 and 4

c) Process 1 and 3

d) Process 2 and 4

7 / 50

7. Choose the incorrect statement:

a) Change in entropy for a irreversible process is greater than zero

b) Change in entropy is zero for a reversible process

c) Both A and B

d) None of these

8 / 50

8. If the temperature of the source is 200°C and that of the sink is 100°C, what is the efficiency of the engine?

a) 0.1

b) 0.2

c) 0.3

d) 0.4

9 / 50

9. During which process does the entropy of the system remain constant?

a) Isobaric

b) Isochoric

c) Isothermal

d) None of these

10 / 50

10. If the temperature of the sink increases, efficiency of the Carnot engine:

a) Increases

b) decreases

c) Remains the same

d) Can't be determined

11 / 50

11. During liquefaction of a gas, entropy of the system -------- and entropy of the surroundings --------

a) Increases, increases

b) Increases, decreases

c) Decreases, increases

d) Decreases, decreases

12 / 50

12. Efficiency of an engine working between the boiling point of water and the melting point of ice is:

a) 0.16

b) .0.38

c) 0.26

d) 0.12

13 / 50

13. Orderness in all natural processes:

a) Increases

b) Decreases

c) Remains the same

d) Can't be determined

14 / 50

14. The equation of efficiency is:

a) Q₁/W

b) Q₂/W

c) W/Q₁

d) W/Q₂

15 / 50

15. Entropy is :

a) A measure of a system’s thermal energy per unit area that is available for useful work

b) Orderness of a system

c) Both A and B

d) None of these

16 / 50

16. To increase the efficiency of a Carnot engine, we should:

a) Decrease the temperature of the source

b) Increase the temperature of the sink

c) Increase the temperature difference between source and sink

d) All of these

17 / 50

17. The SI unit of entropy is:

a) J/K

b) J.K

c) erg/K

d) erg.K

18 / 50

18. Experimental results show that:

a) A cyclic heat engine can be 100% efficient

b) No cyclic heat engine can be 100% efficient

c) All cyclic heat engines are 100% efficient

d) Can't be determined

19 / 50

19. Entropy of the universe during any process:

a) Remains constant

b) Increases

c) Decreases

d) Either A or B

20 / 50

20. If the temperature difference between two reservoirs increases, the efficiency of a Carnot engine:

a) Increases

b) Decreases

c) Remains the same

d) Can't be determined

21 / 50

21. When water boils, which of the following statements is true?

a) Entropy change of system decreases

b) Entropy change of system increases

c) Entropy change of system may increase or decrease

d) Can't be determined

22 / 50

22. Which of the following factors can remain constant at different times during different processes of a Carnot engine?

a) Heat and temperature

b) Pressure and temperature

c) Volume and temperature

d) Heat and pressure

23 / 50

23. Efficiency of a diesel engine is:

a) 25–35%

b) 30–35%

c) 35–40%

d) 40–45%

24 / 50

24. A sequence of processes which leaves the substance in the same state from which it was started is known as:

a) Cyclic process

b) Non-cyclic process

c) Reversible process

d) Irreversible process

25 / 50

25. During which process does entropy not increase?

a) Evaporation

b) Solidification

c) Melting

d) All of these

26 / 50

26. Efficient of heat engine is maximum when:

a) W=0

b) Q1=0

c) Q2=0

d) All of these

27 / 50

27. If heat is removed from a system, thenthe change in entropy of that system is written as

a) Positive

b) Negative

c) Either positive or negative

d) Cant be determined

28 / 50

28. Which of the following is an ideal heat engine?

a) Carnot engine

b) Diesel engine

c) Petrol engine

d) All of these

29 / 50

29. Efficieny of canot engine is independent of

a) Temperature of hot reservoir

b) Temperature of cold reservoir

c) Temperature difference of hot and cold reservoir

d) Nature of working substance

30 / 50

30. Entropy of system is zero at when

a) Temperature is 0k

b) Pressure is 0

c) Both a and b

d) None of these

31 / 50

31. Heat engine converts heat energy into

a) Chemical energy

b) Thermal energy

c) Mechanical energy

d) All of these

32 / 50

32. Efficiency can't be 100% unless____

a) T for hot reservoir is infinite

b) T for cold reservoir is zero

c) T of hot and cold reservoir are equal

d) Cant be determined

33 / 50

33. Q is ____when heat is when heat is released from the working substance and____when absorbed by the working substance

a) Positive,positive

b) positive,negative

c) Negative,positive

d) Negative,negative

34 / 50

34. Efficieny of a heat engine is defined as

a) Ratio of wrokdone by engine to heat absorbed

b) Ratio of wrokdone on engine to heat absorbed

c) Ratio of wrokdone by engine to heat released

d) Ratio of wrokdone on engine to heat released

35 / 50

35. All known natural process are

a) Reversible

b) Irreversible

c) Cyclic

d) Non cyclic

36 / 50

36. Entropy of the environment increases in which of the following processes?

a) Isothermal

b) Isobaric

c) Reversiible

d) Irreversible

37 / 50

37. Which statement shows that all heat cant be converted into heat?

a) Clausius’s statement

b) Kelvin’s statement

c) Carnot’s statement

d) All of these

38 / 50

38. Heat always flows from______

a) Higher to lower energy

b) Lower to higher energy

c) Higher to lower temperature

d) Lower to higher temperature

39 / 50

39. ______the entropy,_________the availability of energy

a) Greater,greater

b) Greater,lesser

c) Lesser,lesser

d) Both are unrelated to eachother

40 / 50

40. A refrigerator is a device which converts________from______to_________body

a) Heat,hot,cold

b) Temperature, hot,cold

c) Heat,cold,hot

d) Temperature, cold,hot

41 / 50

41. If Qh is 300 and Qc is 200,then w is_______

a) 100

b) 200

c) 300

d) 400

42 / 50

42. During transpiration entropy of system

a) Increase

b) Decrease

c) Remaint constant

d) May increase of decrease

43 / 50

43. Which of the following is the correct Sequence of processes in Carnot engine?

a) Isothermal expansion, isothermal compression, adiabatic expansion, adiabatic compression

b) Isothermal expansion,adiabatic expansion,isothermal ,isothermal compression ,adiabatic compression

c) adiabatic expansion ,Isothermal expansion, adiabatic compression, adiabatic expansion, adiabatic compression

d) adiabatic expansion, adiabatic compression ,Isothermal expansion, adiabatic expansion, adiabatic compression

44 / 50

44. When the order increase the the entropy________.

a) Increase

b) Decrease

c) May increase or decrease

d) Cant be determined

45 / 50

45. Which of the following is not true regarding clausius statemnt of second law of thermodynamics

a) Heat can be transferred Low temperature to high temoerature source without using external energy

b) Heat cant be transferred Low temperature to high temoerature source without using external energy

c) Heat can be transferred Low temperature to high temoerature source by using external energy

d) Cant be determined

46 / 50

46. According to Carnot Theorem

The efficiency of the Carnot engine is-----------than any other irreversible heat engine

a) Greater

b) Less

c) Equal

d) May be greater or lesser

47 / 50

47. Area under graph shows:

Area under graph shows

a) Heat absorbed by engine during one complete cycle

b) Heat released by engine during one complete cycle

c) Workdone by engine during one complete cycle

d) Workdone on engine during one complete cycle

48 / 50

48. If a heat engine absorbs 100j energy and 40j out of this is wasted as heat,remaining energy is provided to cold reservoir ,what is efficiency of that engine

a) 0.1

b) 0.6

c) 0.4

d) 0.5

49 / 50

49. A carnot engine working between 400k and 800k has a enegy supplied of 1000j per cycle ,how much work output of engine

a) 100

b) 300

c) 500

d) 1000

50 / 50

50. Heat engines work on the basis of: