Thermodynamics Online Mcqs Test

Mustansar KhanLast Updated: October 13, 2025

Important Physics Thermodynamics Question and Answer

Total Questions:	49
Time Allowed:	25 Minutes
Total Marks:	49
How to Attempt Test:	Please choose the right Option in MCQ-type question.
Test Helpful For:	Physics Test ECAT Test MDCAT Test FPSC/PPSC/SPSC/KPPSC/BPSC/AJKPSC/NTS Physics Interview Question Answer

Physics Thermodynamics Practice Test Online With Explanation

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Page 1 of 2

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1. During isobaric expansion of gas:

No work is done

Volume remains constant

Pressure increases

Pressure remains constant

2. What happens to internal energy during an isothermal expansion?

Decreases

Remains constant

Increases

Becomes negative

3. Which of the following is not a path function?

Internal energy

Work

Heat

All of the above

4. In an adiabatic process, if work is positive:

Internal energy decreases

Temperature remains constant

Internal energy remains unchanged

Internal energy increases

5. Which law defines the mechanical equivalent of heat?

Newton's law

First law of thermodynamics

Law of conservation of momentum

Boyle’s law

6. Which thermodynamic process has both Q and W equal to zero?

Isothermal

Isochoric

Adiabatic

Free expansion

7. In the first law of thermodynamics, the internal energy change is equal to:

Pressure × Volume

Heat added to the system

Heat added minus work done

Work done by the system

8. What happens to the internal energy in an adiabatic expansion?

Becomes zero

Increases

Doubles

Decreases

9. Which of the following expresses work done at constant pressure?

W = PΔV

W = Q

W = ΔU

W = PV

10. What is the heat required to raise the temperature of 5 kg of a substance with specific heat 200 J/kg·K by 3 K?

3000 J

9000 J

1000 J

600 J

11. What is specific heat?

Heat required to raise temperature of 1 kg by 1 K

Heat required to change state

Heat required for melting

Heat required to increase pressure

12. Which law states that energy can neither be created nor destroyed?

Zeroth law of thermodynamics

Second law of thermodynamics

First law of thermodynamics

Third law of thermodynamics

13. Which of the following statements is true about heat?

It flows from cold to hot

It is a form of matter

It is stored in the body

It flows from hot to cold

14. Which of the following has the highest specific heat?

Copper

Iron

Water

Mercury

15. If Q = 200 J and W = 50 J, what is the change in internal energy?

300 J

250 J

150 J

100 J

16. Which physical quantity is represented by the slope of a temperature vs. heat graph during heating?

Latent heat

Specific heat

Internal energy

Pressure

17. What is the heat capacity of a substance?

Volume × density

Heat required to change state

Heat required to raise temperature by 1°C

Mass × temperature

18. When a gas is compressed, work is:

Zero

Done on the gas

Done by the gas

Infinite

19. What does the term “internal energy” refer to?

Energy due to external force

Total kinetic and potential energy of molecules

Heat energy only

Energy required for phase change

20. What does a negative ΔU indicate?

Temperature increases

Energy is absorbed

Internal energy has decreased

System has gained energy

21. What is the value of specific heat of water?

0.42 J/kg·K

420 J/kg·K

4.2 J/kg·K

4200 J/kg·K

22. When a system performs positive work, it means:

Energy is released by the system

Pressure increases

Volume decreases

Energy is added to the system

23. Molar specific heat is the amount of heat required to:

Raise the temperature of 1 mole by 1°C

Melt one mole of substance

Boil one mole of water

Freeze one mole of liquid

24. The total energy of an isolated system:

Increases

Remains constant

Decreases

Becomes zero

25. The heat required to raise the temperature of one mole of a substance by one Kelvin is:

Latent heat

Specific heat

Molar heat capacity

Thermal conductivity

Page 2 of 2

26. The temperature of a gas is directly proportional to:

Internal energy

Volume

Pressure only

Mass

27. The first law of thermodynamics violates:

Destruction of mass

Conservation of energy

Creation of energy

Conservation of momentum

28. When a gas expands doing work and absorbs heat, its internal energy:

Increases

Decreases

Remains the same

Becomes zero

29. Which process occurs without any change in heat content?

Isochoric

Isobaric

Isothermal

Adiabatic

30. The SI unit of heat is:

Calorie

Watt

Joule

Kelvin

31. Which gas law is used in the derivation of the first law of thermodynamics?

Charles’s law

Ideal gas law

Dalton’s law

Boyle’s law

32. Which of the following is an extensive property?

Specific heat

Internal energy

Pressure

Temperature

33. When W = Q in the first law equation, what is ΔU?

Maximum

Zero

Equal to heat

Minimum

34. Which of the following has units J/mol·K?

Molar specific heat

Internal energy

Pressure

Specific heat

35. What does an isothermal process imply?

Constant volume

Constant temperature

Constant pressure

Constant entropy

36. Which process shows ΔU = 0?

Isobaric

Isothermal

Isochoric

Adiabatic

37. In a system where no heat is added and work is done on the gas, internal energy:

Becomes zero

Remains same

Increases

Decreases

38. If no heat is exchanged with the surroundings, the process is called:

Isobaric

Adiabatic

Isothermal

Isochoric

39. Which of the following has the highest molar specific heat at constant pressure?

Metals

Water

Diatomic gases

Monoatomic gases

40. Which of the following processes occurs at constant volume?

Isobaric

Isothermal

Isochoric

Adiabatic

41. What is the heat added in an adiabatic process?

Infinite

Equal to work done

Zero

Constant

42. Which equation represents the first law of thermodynamics?

Q = mcΔT

F = ma

PV = nRT

ΔU = Q – W

43. What is the unit of specific heat in SI?

J/kg

J/kg·K

J/K

J/mol·K

44. Which of the following is a state function?

Work

Path

Internal energy

Heat

45. Which of the following does not change during an isothermal process?

Temperature

Pressure

Volume

Heat

46. In the equation ΔU = Q – W, what does a positive W indicate?

Work done on the system

No work

Work done by the system

Heat absorbed

47. Specific heat is lowest for:

Lead

Aluminum

Iron

Water

48. In which process is ΔU = Q?

Isochoric

Adiabatic

Isothermal

Isobaric

49. Which instrument is used to measure heat?

Barometer

Thermometer

Calorimeter

Voltmeter

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Mustansar KhanLast Updated: October 13, 2025

Important Physics Thermodynamics Question and Answer

Physics Thermodynamics Practice Test Online With Explanation

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