Q. For a monatomic ideal gas, the ratio of specific heats (γ) is approximately: (2019)
A.
1.5
B.
1.67
C.
1.4
D.
2
Show solution
Solution
For a monatomic ideal gas, γ = C_p/C_v = 5/3 = 1.67.
Correct Answer:
B
— 1.67
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Q. For a process at constant volume, which of the following is true? (2023)
A.
Work done is zero
B.
Heat added equals change in internal energy
C.
Both A and B
D.
None of the above
Show solution
Solution
At constant volume, no work is done (W=0), and the heat added equals the change in internal energy (Q=ΔU).
Correct Answer:
C
— Both A and B
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Q. For an ideal gas, the work done during an isobaric process is given by which formula? (2022)
A.
W = PΔV
B.
W = nRT
C.
W = ΔU + Q
D.
W = 0
Show solution
Solution
In an isobaric process, the work done is calculated using the formula W = PΔV, where P is pressure and ΔV is the change in volume.
Correct Answer:
A
— W = PΔV
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Q. For an ideal gas, which law relates pressure, volume, and temperature? (2023) 2023
A.
Boyle's Law
B.
Charles's Law
C.
Ideal Gas Law
D.
Avogadro's Law
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Solution
The Ideal Gas Law (PV = nRT) relates pressure (P), volume (V), and temperature (T) for an ideal gas.
Correct Answer:
C
— Ideal Gas Law
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Q. In a Carnot engine operating between temperatures T1 and T2, what is the efficiency (η) of the engine? (2023)
A.
1 - T2/T1
B.
T1/T2
C.
T2/T1
D.
T1 - T2
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Solution
The efficiency of a Carnot engine is given by η = 1 - T2/T1.
Correct Answer:
A
— 1 - T2/T1
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Q. In a Carnot engine, the efficiency depends on which of the following? (2023)
A.
Temperature of the hot reservoir
B.
Temperature of the cold reservoir
C.
Both temperatures
D.
Type of working substance
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Solution
The efficiency of a Carnot engine is determined by the temperatures of the hot and cold reservoirs, given by the formula η = 1 - (T_c/T_h).
Correct Answer:
C
— Both temperatures
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Q. In a closed system, if 100 J of heat is added and 40 J of work is done by the system, what is the change in internal energy? (2022)
A.
60 J
B.
40 J
C.
100 J
D.
Zero
Show solution
Solution
According to the First Law of Thermodynamics, ΔU = Q - W. Here, ΔU = 100 J - 40 J = 60 J.
Correct Answer:
A
— 60 J
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Q. In a cyclic process, the net work done is equal to: (2020)
A.
Net heat added
B.
Change in internal energy
C.
Zero
D.
Net heat removed
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Solution
In a cyclic process, the net work done is equal to the net heat added to the system, as the internal energy returns to its initial state.
Correct Answer:
A
— Net heat added
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Q. In a heat engine, if the input heat is 500 J and the work done is 300 J, what is the efficiency? (2023) 2023
A.
60%
B.
50%
C.
40%
D.
70%
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Solution
Efficiency (η) = Work done / Input heat = 300 J / 500 J = 0.6 or 60%.
Correct Answer:
A
— 60%
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Q. In an adiabatic process, the relationship between pressure and volume for an ideal gas is given by which equation? (2020)
A.
PV^n = constant
B.
PV = nRT
C.
P1V1 = P2V2
D.
V/T = constant
Show solution
Solution
In an adiabatic process, the relationship is given by PV^n = constant, where n is the heat capacity ratio.
Correct Answer:
A
— PV^n = constant
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Q. In an adiabatic process, which of the following is true? (2020)
A.
Heat is absorbed from the surroundings
B.
Heat is released to the surroundings
C.
No heat is exchanged
D.
Temperature remains constant
Show solution
Solution
In an adiabatic process, there is no heat exchange with the surroundings, meaning no heat is absorbed or released.
Correct Answer:
C
— No heat is exchanged
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Q. In an adiabatic process, which of the following remains constant? (2020)
A.
Temperature
B.
Pressure
C.
Internal Energy
D.
Enthalpy
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Solution
In an adiabatic process, there is no heat exchange, so the internal energy remains constant for an ideal gas.
Correct Answer:
C
— Internal Energy
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Q. In an isothermal process, the temperature of the gas remains constant. What can be said about the internal energy of an ideal gas? (2020) 2020
A.
It increases
B.
It decreases
C.
It remains constant
D.
It varies with pressure
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Solution
For an ideal gas, the internal energy depends only on temperature. Since the temperature remains constant in an isothermal process, the internal energy also remains constant.
Correct Answer:
C
— It remains constant
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Q. In an isothermal process, the temperature of the system remains: (2023)
A.
Constant
B.
Increases
C.
Decreases
D.
Varies
Show solution
Solution
In an isothermal process, the temperature of the system remains constant.
Correct Answer:
A
— Constant
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Q. What does the term 'enthalpy' refer to? (2020)
A.
Internal energy plus pressure times volume
B.
Heat content of a system at constant pressure
C.
Total energy of a system
D.
Work done by the system
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Solution
Enthalpy refers to the heat content of a system at constant pressure, defined as internal energy plus pressure times volume.
Correct Answer:
B
— Heat content of a system at constant pressure
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Q. What happens to the entropy of an isolated system? (2020) 2020
A.
It decreases
B.
It remains constant
C.
It increases
D.
It can either increase or decrease
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Solution
According to the second law of thermodynamics, the entropy of an isolated system always increases over time.
Correct Answer:
C
— It increases
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Q. What happens to the temperature of a gas during an isothermal expansion? (2021)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Varies with pressure
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Solution
During an isothermal expansion, the temperature of the gas remains constant as the system absorbs heat to do work.
Correct Answer:
C
— Remains constant
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Q. What is the change in internal energy (ΔU) for an ideal gas that expands isothermally? (2022)
A.
0
B.
nRT
C.
nRΔT
D.
PV
Show solution
Solution
For an isothermal process, the change in internal energy ΔU = 0 for an ideal gas.
Correct Answer:
A
— 0
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Q. What is the change in internal energy for an ideal gas that expands isothermally? (2019)
A.
nRT
B.
0
C.
-nRT
D.
nR(Tf - Ti)
Show solution
Solution
For an isothermal process, the change in internal energy (ΔU) for an ideal gas is zero, as ΔU depends only on temperature.
Correct Answer:
B
— 0
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Q. What is the change in internal energy of an ideal gas when it expands isothermally? (2021)
A.
Zero
B.
Positive
C.
Negative
D.
Depends on the gas
Show solution
Solution
In an isothermal process for an ideal gas, the internal energy remains constant, hence the change in internal energy is zero.
Correct Answer:
A
— Zero
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Q. What is the change in internal energy of an ideal gas when it is heated at constant volume? (2021) 2021
A.
Zero
B.
Equal to heat added
C.
Equal to work done
D.
Equal to pressure times volume
Show solution
Solution
At constant volume, the change in internal energy (ΔU) is equal to the heat added (Q). Therefore, ΔU = Q.
Correct Answer:
B
— Equal to heat added
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Q. What is the efficiency of a Carnot engine operating between temperatures T1 and T2? (2019) 2019
A.
(T1 - T2) / T1
B.
T2 / T1
C.
(T1 - T2) / T2
D.
1 - (T2 / T1)
Show solution
Solution
The efficiency (η) of a Carnot engine is given by η = 1 - (T2 / T1), where T1 is the higher temperature and T2 is the lower temperature.
Correct Answer:
D
— 1 - (T2 / T1)
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Q. What is the specific heat at constant volume (Cv) for a monatomic ideal gas? (2019)
A.
3R/2
B.
5R/2
C.
R
D.
2R
Show solution
Solution
For a monatomic ideal gas, the specific heat at constant volume (Cv) is 3R/2.
Correct Answer:
A
— 3R/2
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Q. What is the specific heat capacity of water at constant pressure (C_p)? (2020)
A.
4.18 J/g°C
B.
2.09 J/g°C
C.
1.00 J/g°C
D.
3.00 J/g°C
Show solution
Solution
The specific heat capacity of water at constant pressure is approximately 4.18 J/g°C.
Correct Answer:
A
— 4.18 J/g°C
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Q. What is the specific heat capacity of water? (2021) 2021
A.
1 J/g°C
B.
4.18 J/g°C
C.
2 J/g°C
D.
0.9 J/g°C
Show solution
Solution
The specific heat capacity of water is approximately 4.18 J/g°C.
Correct Answer:
B
— 4.18 J/g°C
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Q. What is the work done by an ideal gas during an isothermal expansion from volume V1 to V2 at temperature T? (2021)
A.
nRT ln(V2/V1)
B.
nRT (V2 - V1)
C.
PV
D.
0
Show solution
Solution
The work done during an isothermal expansion is given by W = nRT ln(V2/V1).
Correct Answer:
A
— nRT ln(V2/V1)
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Q. What is the work done by an ideal gas during isothermal expansion? (2021)
A.
0
B.
nRT ln(Vf/Vi)
C.
nRT (Vf - Vi)
D.
nR (Tf - Ti)
Show solution
Solution
For an ideal gas undergoing isothermal expansion, the work done is given by W = nRT ln(Vf/Vi).
Correct Answer:
B
— nRT ln(Vf/Vi)
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Q. Which law states that energy cannot be created or destroyed, only transformed? (2021)
A.
Zeroth Law
B.
First Law
C.
Second Law
D.
Third Law
Show solution
Solution
The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed.
Correct Answer:
B
— First Law
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Q. Which of the following processes is irreversible? (2022)
A.
Isothermal expansion
B.
Adiabatic expansion
C.
Free expansion
D.
Isobaric process
Show solution
Solution
Free expansion is an irreversible process as it occurs without any external pressure acting on the gas.
Correct Answer:
C
— Free expansion
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Q. Which of the following processes is isochoric? (2023)
A.
Constant volume
B.
Constant pressure
C.
Constant temperature
D.
Adiabatic
Show solution
Solution
An isochoric process is one that occurs at constant volume.
Correct Answer:
A
— Constant volume
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Showing 1 to 30 of 32 (2 Pages)
Thermodynamics MCQ & Objective Questions
Thermodynamics is a crucial topic in physics that plays a significant role in various school and competitive exams. Understanding the principles of thermodynamics not only enhances your conceptual clarity but also boosts your confidence in tackling exam questions. Practicing MCQs and objective questions on thermodynamics is essential for effective exam preparation, helping you identify important questions and improve your problem-solving skills.
What You Will Practise Here
Key laws of thermodynamics: First, Second, and Third Laws
Thermodynamic processes: Isothermal, Adiabatic, and Isochoric
Heat engines and refrigerators: Efficiency calculations
Concepts of entropy and enthalpy
Thermodynamic cycles: Carnot cycle and its applications
Real-world applications of thermodynamics in engineering and science
Important formulas and definitions related to thermodynamic systems
Exam Relevance
Thermodynamics is a vital topic in the curriculum of CBSE, State Boards, NEET, and JEE. Students can expect questions related to the laws of thermodynamics, calculations involving heat engines, and conceptual problems on entropy and enthalpy. Common question patterns include numerical problems, theoretical questions, and application-based scenarios, making it essential to master this topic for scoring well in exams.
Common Mistakes Students Make
Confusing the different thermodynamic processes and their characteristics
Misunderstanding the concept of entropy and its implications
Incorrectly applying formulas for efficiency in heat engines
Overlooking the significance of units in thermodynamic calculations
FAQs
Question: What are the main laws of thermodynamics?Answer: The main laws are the First Law (conservation of energy), the Second Law (entropy increases in isolated systems), and the Third Law (entropy approaches a constant value as temperature approaches absolute zero).
Question: How can I improve my understanding of thermodynamics for exams?Answer: Regular practice of thermodynamics MCQ questions and objective questions with answers will help reinforce your understanding and prepare you for exam scenarios.
Start solving practice MCQs on thermodynamics today to test your understanding and enhance your exam readiness. Remember, consistent practice is the key to mastering this essential topic!
