Heat and Thermodynamics MCQs (Level 2) – 100 Advanced & Numerical MCQs with Answers

100 Advanced & Numerical MCQs (Level -2) on Heat and Thermodynamics, Physics (Unit-Wise MCQs Practice):

---

---

👉Physics MCQs Hub – Unit wise Physics MCQs Practice (Main-Page)👈

---

Whether you are preparing for board examinations, chapter tests, college assessments, or competitive entrance exams (MDCAT, ECAT, NUST, PIEAS, GIKI, UET, FAST, and other engineering or medical admission tests), this comprehensive Heat and Thermodynamics MCQ Collection is designed to help you master one of the most important and widely tested chapters in physics. The questions are arranged progressively—from fundamental concepts to advanced numerical problems and higher-order thinking—ensuring complete and systematic preparation for every type of examination.

This chapter-wise MCQ collection includes:

100 Basic MCQs Level-1 (1–100) – Covering the fundamental concepts of heat and temperature, thermal equilibrium, thermometers, thermal expansion, specific heat capacity, latent heat, calorimetry, heat transfer, kinetic theory of gases, gas laws, and introductory thermodynamics.

100 Advanced & Numerical MCQs (101–200) – Focusing on heat calculations, calorimetry, thermal expansion, gas equations, the First and Second Laws of Thermodynamics, work done by gases, internal energy, Carnot engine, refrigerator, coefficient of performance (COP), entropy, and exam-oriented numerical problems.

50 Higher-Order Thinking Skills (HOTS) MCQs (201–250) – Designed to strengthen analytical reasoning, conceptual understanding, case-based learning, assertion–reason questions, thermodynamic cycle analysis, Carnot engine applications, entropy concepts, and advanced problem-solving skills.

50 Challenging MCQs Quiz with Answers – A carefully selected collection of the most important conceptual, numerical, and HOTS questions with detailed explanations for quick revision, self-assessment, and complete exam preparation.

This MCQ collection covers:

• Heat, temperature, and thermal equilibrium
• Thermometers and temperature scales (Celsius, Fahrenheit, Kelvin)
• Thermal expansion of solids, liquids, and gases
• Specific heat capacity and calorimetry
• Change of state and latent heat
• Heat transfer by conduction, convection, and radiation
• Kinetic theory of gases and molecular interpretation of heat
• Boyle's Law, Charles's Law, Gay-Lussac's Law, and the Ideal Gas Equation
• Internal energy and mechanical equivalent of heat
• First Law of Thermodynamics and conservation of energy
• Isothermal, adiabatic, isobaric, and isochoric processes
• Heat engines, Carnot engine, and Carnot cycle
• Refrigerators, heat pumps, and coefficient of performance (COP)
• Second and Third Laws of Thermodynamics
• Entropy, reversible and irreversible processes
• Pressure-volume (P–V) diagrams and thermodynamic cycles
• Practical engineering applications of thermodynamics
• Real-life applications of heat transfer and thermal systems

Every MCQ includes the correct answer along with a clear, concept-based explanation to strengthen understanding, improve problem-solving skills, and reinforce key physics concepts.

This question bank helps students to:

• Build a strong conceptual foundation in heat and thermodynamics
• Master thermal expansion, calorimetry, and gas laws
• Develop confidence in solving numerical and analytical problems
• Understand thermodynamic processes and energy transformations
• Learn the working principles of heat engines, refrigerators, and heat pumps
• Strengthen concepts of entropy, Carnot cycle, and thermodynamic laws
• Avoid common examination mistakes through concept-based practice
• Increase speed, accuracy, and confidence in objective-type questions
• Prepare effectively for both board examinations and competitive entrance tests

With 250 carefully selected MCQs arranged into 100 Basic, 100 Advanced & Numerical, and 50 Higher-Order Thinking Skills (HOTS) questions, along with a Top 50 Challenging MCQs Quiz, this all-in-one MCQ bank provides complete preparation for Heat and Thermodynamics. It is an excellent study resource for strengthening conceptual understanding, improving numerical problem-solving skills, enhancing exam performance, and achieving success in both school examinations and highly competitive engineering and medical entrance tests.

---

Best Budget Laptops for Students for Study, Coding & Office Work 
(2026 Amazon Deals)

👉 Check Today’s Price on Amazon👈

👉 Check Acer Aspire 5 Price on Amazon

👉 Buy Lenovo IdeaPad Slim 3 on Amazon

👉 See HP Pavilion Latest Deal on Amazon

👉 View ASUS Vivobook 16 Details on Amazon

👉 Check MacBook Air Student Price on Amazon

---

Heat and Thermodynamics MCQs (Level 2) – 100 Advanced & Numerical MCQs (MCQs 101–200)

---

MCQ No. 101

A gas absorbs 600 J of heat and performs 250 J of work. The increase in its internal energy is:

a) 250 J

b) 350 J

c) 600 J

d) 850 J

Correct Answer: b) 350 J

Explanation:
According to the First Law of Thermodynamics,

$$\Delta U = Q - W$$
$$\Delta U = 600 - 250 = 350\text{ J}$$

Therefore, the internal energy increases by 350 J.

---

MCQ No. 102

A system receives 900 J of heat and its internal energy increases by 500 J. The work done by the system is:

a) 400 J

b) 500 J

c) 900 J

d) 1400 J

Correct Answer: a) 400 J

Explanation:

Using

$$Q=\Delta U+W$$
$$W=900-500=400\text{ J}$$

---

MCQ No. 103

If a gas does 300 J of work without absorbing any heat, the change in its internal energy is:

a) +300 J

b) −300 J

c) Zero

d) +600 J

Correct Answer: b) −300 J

Explanation:

For an adiabatic process,

$$Q=0$$

Hence,

$$\Delta U=0-300=-300\text{ J}$$

The internal energy decreases by 300 J.

---

MCQ No. 104

A gas absorbs 450 J of heat while 150 J of work is done on the gas. The increase in internal energy is:

a) 300 J

b) 450 J

c) 600 J

d) 150 J

Correct Answer: c) 600 J

Explanation:

When work is done on the gas,

$$\Delta U=Q+W$$
$$=450+150=600\text{ J}$$

---

MCQ No. 105

A gas expands at constant pressure of $2\times10^5$  Pa. If its volume increases by $0.02\,m^3$ , the work done is:

a) 2000 J

b) 3000 J

c) 4000 J

d) 5000 J

Correct Answer: c) 4000 J

Explanation:

$$W=P\Delta V$$
$$=(2\times10^5)(0.02) =4000\text{ J}$$

---

MCQ No. 106

A gas expands from 3 m³ to 5 m³ under a constant pressure of 500 Pa. The work done is:

a) 500 J

b) 1000 J

c) 1500 J

d) 2500 J

Correct Answer: b) 1000 J

Explanation:

$$W=P\Delta V$$
$$=500(5-3) =1000\text{ J}$$

---

MCQ No. 107

If the volume of a gas remains constant, the work done by the gas is:

a) Positive

b) Negative

c) Zero

d) Infinite

Correct Answer: c) Zero

Explanation:

Since

$$\Delta V=0$$

therefore,

$$W=P\Delta V=0$$

---

MCQ No. 108

A gas absorbs 1000 J of heat at constant volume. The increase in internal energy is:

a) Zero

b) 500 J

c) 1000 J

d) 2000 J

Correct Answer: c) 1000 J

Explanation:

At constant volume,

$$W=0$$

Therefore,

$$\Delta U=Q=1000\text{ J}$$

---

MCQ No. 109

During an isothermal process of an ideal gas, the change in internal energy is:

a) Positive

b) Negative

c) Zero

d) Cannot be determined

Correct Answer: c) Zero

Explanation:

For an ideal gas,

Internal energy depends only on temperature.

Since temperature remains constant,

$$\Delta U=0$$

---

MCQ No. 110

If an ideal gas absorbs 700 J of heat during an isothermal expansion, the work done by the gas is:

a) 0 J

b) 350 J

c) 700 J

d) 1400 J

Correct Answer: c) 700 J

Explanation:

For an isothermal process,

$$\Delta U=0$$

Hence,

$$Q=W=700\text{ J}$$

---

MCQ No. 111

The SI unit of molar specific heat capacity is:

a) J kg⁻¹ K⁻¹

b) J mol⁻¹ K⁻¹

c) cal g⁻¹ °C⁻¹

d) W K⁻¹

Correct Answer: b) J mol⁻¹ K⁻¹

Explanation:

Molar specific heat capacity is measured in joules per mole per kelvin (J mol⁻¹ K⁻¹).

---

MCQ No. 112

According to Mayer's relation for an ideal gas:

a) $C_P+C_V=R$

b) $C_P-C_V=R$

c) $C_P=C_V-R$

d) $C_P=C_V$

Correct Answer: b) $C_P-C_V=R$

Explanation:

For an ideal gas,

$$C_P-C_V=R$$

---

MCQ No. 113

The value of the universal gas constant is approximately:

a) 1.38 J mol⁻¹ K⁻¹

b) 4.18 J mol⁻¹ K⁻¹

c) 8.31 J mol⁻¹ K⁻¹

d) 9.81 J mol⁻¹ K⁻¹

Correct Answer: c) 8.31 J mol⁻¹ K⁻¹

Explanation:

The universal gas constant is

$$R=8.31\text{ J mol}^{-1}\text{K}^{-1}$$

---

MCQ No. 114

If $C_V=20.8\;J\,mol^{-1}K^{-1}$ , then $C_P$ is approximately:

a) 20.8

b) 25.0

c) 29.1

d) 31.5

Correct Answer: c) 29.1

Explanation:

Using

$$C_P=C_V+R$$
$$=20.8+8.31 =29.11$$

---

MCQ No. 115

If $C_P=29.1\;J\,mol^{-1}K^{-1}$  and $C_V=20.8\;J\,mol^{-1}K^{-1}$ , then the value of $R$  is:

a) 6.2

b) 7.5

c) 8.3

d) 9.6

Correct Answer: c) 8.3

Explanation:

$$R=C_P-C_V$$
$$=29.1-20.8 =8.3$$

---

MCQ No. 116

The ratio $C_P/C_V$ for a monoatomic ideal gas is approximately:

a) 1.20

b) 1.33

c) 1.40

d) 1.67

Correct Answer: d) 1.67

Explanation:

For monoatomic gases,

$$\gamma=\frac53\approx1.67$$

---

MCQ No. 117

Which thermodynamic process has zero work done?

a) Isothermal

b) Isobaric

c) Isochoric

d) Adiabatic expansion

Correct Answer: c) Isochoric

Explanation:

At constant volume,

$$W=P\Delta V=0$$

---

MCQ No. 118

During an adiabatic expansion, which quantity remains constant?

a) Pressure

b) Temperature

c) Heat exchanged

d) Volume

Correct Answer: c) Heat exchanged

Explanation:

In an adiabatic process,

$$Q=0$$

No heat enters or leaves the system.

---

MCQ No. 119

Which thermodynamic process is represented by a horizontal line on a P–V graph?

a) Isochoric

b) Isothermal

c) Isobaric

d) Adiabatic

Correct Answer: c) Isobaric

Explanation:

A horizontal line indicates constant pressure.

---

MCQ No. 120

The area under a P–V curve represents the:

a) Internal energy

b) Heat supplied

c) Work done

d) Temperature change

Correct Answer: c) Work done

Explanation:

The area under the pressure-volume curve gives the mechanical work done by or on the gas during the thermodynamic process.

---

MCQ No. 121

A 2 kg copper block (specific heat capacity = 390 J kg⁻¹ K⁻¹) is heated through 20 K. The heat absorbed is:

a) 7,800 J

b) 15,600 J

c) 31,200 J

d) 39,000 J

Correct Answer: b) 15,600 J

Explanation:

Using,

$$Q = mc\Delta T$$
$$Q = 2 \times 390 \times 20 = 15,600\ \text{J}$$

---

MCQ No. 122

A body absorbs 10,000 J of heat, and its temperature rises by 25°C. If its mass is 4 kg, the specific heat capacity is:

a) 50 J kg⁻¹ K⁻¹

b) 100 J kg⁻¹ K⁻¹

c) 200 J kg⁻¹ K⁻¹

d) 400 J kg⁻¹ K⁻¹

Correct Answer: b) 100 J kg⁻¹ K⁻¹

Explanation:

$$c=\frac{Q}{m\Delta T}$$
$$=\frac{10000}{4\times25}=100\ \text{J kg}^{-1}\text{K}^{-1}$$

---

MCQ No. 123

How much heat is required to raise the temperature of 5 kg of water by 10 K? (Specific heat capacity of water = 4200 J kg⁻¹ K⁻¹)

a) 42,000 J

b) 84,000 J

c) 105,000 J

d) 210,000 J

Correct Answer: d) 210,000 J

Explanation:

$$Q=mc\Delta T$$
$$=5\times4200\times10=210,000\ \text{J}$$

---

MCQ No. 124

One mole of an ideal gas has $C_V = 20.8\;J\,mol^{-1}K^{-1}$ . If its temperature increases by 15 K at constant volume, the heat supplied is:

a) 156 J

b) 208 J

c) 312 J

d) 624 J

Correct Answer: c) 312 J

Explanation:

At constant volume,

$$Q=nC_V\Delta T$$
$$=1\times20.8\times15=312\ \text{J}$$

---

MCQ No. 125

One mole of an ideal gas has $C_P = 29.1\;J\,mol^{-1}K^{-1}$ . If its temperature rises by 20 K at constant pressure, the heat supplied is:

a) 291 J

b) 420 J

c) 582 J

d) 874 J

Correct Answer: c) 582 J

Explanation:

$$Q=nC_P\Delta T$$
$$=1\times29.1\times20=582\ \text{J}$$

---

MCQ No. 126

A gas receives 1500 J of heat while doing 600 J of work. Its increase in internal energy is:

a) 600 J

b) 900 J

c) 1500 J

d) 2100 J

Correct Answer: b) 900 J

Explanation:

$$\Delta U=Q-W$$
$$=1500-600=900\ \text{J}$$

---

MCQ No. 127

A gas performs 500 J of work while its internal energy decreases by 200 J. The heat supplied to the gas is:

a) 200 J

b) 300 J

c) 500 J

d) 700 J

Correct Answer: b) 300 J

Explanation:

Using

$$Q=\Delta U+W$$
$$=(-200)+500=300\ \text{J}$$

---

MCQ No. 128

The efficiency of a heat engine that produces 400 J of work after absorbing 1000 J of heat is:

a) 20%

b) 30%

c) 40%

d) 60%

Correct Answer: c) 40%

Explanation:

$$\eta=\frac{W}{Q_H}\times100$$
$$=\frac{400}{1000}\times100=40\%$$

---

MCQ No. 129

A heat engine absorbs 2000 J of heat and rejects 1400 J to the sink. Its efficiency is:

a) 20%

b) 25%

c) 30%

d) 40%

Correct Answer: c) 30%

Explanation:

Work done,

$$W=Q_H-Q_C$$
$$=2000-1400=600\ \text{J}$$

Efficiency,

$$\eta=\frac{600}{2000}\times100=30\%$$

---

MCQ No. 130

A Carnot engine operates between 600 K and 300 K. Its maximum efficiency is:

a) 25%

b) 40%

c) 50%

d) 75%

Correct Answer: c) 50%

Explanation:

$$\eta=1-\frac{T_C}{T_H}$$
$$=1-\frac{300}{600}=0.5$$

Efficiency = 50%

---

MCQ No. 131

A Carnot engine works between temperatures of 800 K and 400 K. Its efficiency is:

a) 40%

b) 50%

c) 60%

d) 75%

Correct Answer: b) 50%

Explanation:

$$\eta=1-\frac{400}{800}=0.5$$

---

MCQ No. 132

A Carnot engine has an efficiency of 60%. If the hot reservoir is at 750 K, the cold reservoir temperature is:

a) 150 K

b) 200 K

c) 300 K

d) 450 K

Correct Answer: c) 300 K

Explanation:

$$0.60=1-\frac{T_C}{750}$$
$$T_C=300\ \text{K}$$

---

MCQ No. 133

A refrigerator removes 1200 J of heat while consuming 300 J of work. Its coefficient of performance (COP) is:

a) 2

b) 3

c) 4

d) 5

Correct Answer: c) 4

Explanation:

$$COP=\frac{Q_L}{W}$$
$$=\frac{1200}{300}=4$$

---

MCQ No. 134

A refrigerator has a COP of 5 and consumes 200 J of work. The heat removed from the cold reservoir is:

a) 200 J

b) 600 J

c) 800 J

d) 1000 J

Correct Answer: d) 1000 J

Explanation:

$$Q_L=COP\times W$$
$$=5\times200=1000\ \text{J}$$

---

MCQ No. 135

A Carnot refrigerator operates between 270 K and 300 K. Its COP is approximately:

a) 5

b) 7

c) 9

d) 10

Correct Answer: c) 9

Explanation:

For a Carnot refrigerator,

$$COP=\frac{T_C}{T_H-T_C}$$
$$=\frac{270}{300-270} =\frac{270}{30}=9$$

---

MCQ No. 136

If the entropy of a system increases by 25 J K⁻¹ during a process, the process is most likely:

a) Spontaneous

b) Impossible

c) Perfectly reversible only

d) At absolute zero

Correct Answer: a) Spontaneous

Explanation:
Natural spontaneous processes are generally accompanied by an increase in entropy.

---

MCQ No. 137

A reversible heat engine operates between the same two temperatures as a real engine. Compared with the real engine, it will have:

a) Lower efficiency

b) Equal efficiency

c) Higher efficiency

d) Zero efficiency

Correct Answer: c) Higher efficiency

Explanation:
A reversible (Carnot) engine has the maximum possible efficiency for a given pair of reservoir temperatures.

---

MCQ No. 138

If the hot reservoir temperature increases while the cold reservoir temperature remains constant, the Carnot efficiency will:

a) Increase

b) Decrease

c) Remain unchanged

d) Become zero

Correct Answer: a) Increase

Explanation:
According to

$$\eta=1-\frac{T_C}{T_H},$$

increasing $T_H$ increases the efficiency.

---

MCQ No. 139

During an isochoric process, which of the following quantities is always zero?

a) Pressure

b) Heat supplied

c) Internal energy

d) Work done

Correct Answer: d) Work done

Explanation:
Since the volume remains constant,

$$W=P\Delta V=0.$$

---

MCQ No. 140

Which thermodynamic process is most suitable for minimizing heat exchange with the surroundings?

a) Isothermal process

b) Isobaric process

c) Isochoric process

d) Adiabatic process

Correct Answer: d) Adiabatic process

Explanation:
In an adiabatic process,

$$Q=0,$$

meaning there is no heat exchange between the system and its surroundings.

---

MCQ No. 141

An ideal gas expands at a constant pressure of $1.5\times10^5$ Pa. If its volume increases from 0.020 m³ to 0.050 m³, the work done is:

a) 3000 J

b) 3500 J

c) 4500 J

d) 5000 J

Correct Answer: c) 4500 J

Explanation:

At constant pressure,

$$W=P\Delta V$$
$$=(1.5\times10^5)(0.050-0.020)$$
$$=1.5\times10^5\times0.03 =4500\text{ J}$$

---

MCQ No. 142

A gas absorbs 2500 J of heat and its internal energy increases by 1700 J. The work done by the gas is:

a) 500 J

b) 700 J

c) 800 J

d) 4200 J

Correct Answer: c) 800 J

Explanation:

Using the First Law,

$$Q=\Delta U+W$$
$$W=2500-1700=800\text{ J}$$

---

MCQ No. 143

A gas performs 900 J of work while 600 J of heat leaves the system. The change in internal energy is:

a) –1500 J

b) –300 J

c) +300 J

d) +1500 J

Correct Answer: a) –1500 J

Explanation:

Heat leaving the system means

$$Q=-600\text{ J}$$

Therefore,

$$\Delta U=Q-W$$
$$=-600-900=-1500\text{ J}$$

---

MCQ No. 144

If the internal energy of an ideal gas remains constant during a process, the process must be:

a) Isobaric

b) Isochoric

c) Isothermal

d) Adiabatic

Correct Answer: c) Isothermal

Explanation:

For an ideal gas, internal energy depends only on temperature. Constant internal energy implies constant temperature.

---

MCQ No. 145

A gas receives 1200 J of heat and performs 1200 J of work. The change in internal energy is:

a) 0 J

b) 600 J

c) 1200 J

d) –1200 J

Correct Answer: a) 0 J

Explanation:

$$\Delta U=Q-W$$
$$=1200-1200=0$$

---

MCQ No. 146

A gas is compressed adiabatically. Which quantity increases?

a) Volume

b) Temperature

c) Entropy

d) Heat transferred

Correct Answer: b) Temperature

Explanation:

During adiabatic compression, work is done on the gas. Its internal energy and temperature increase.

---

MCQ No. 147

A Carnot engine operates between 900 K and 300 K. Its maximum efficiency is:

a) 33.3%

b) 50%

c) 66.7%

d) 75%

Correct Answer: c) 66.7%

Explanation:

$$\eta=1-\frac{T_C}{T_H}$$
$$=1-\frac{300}{900} =\frac23 =66.7\%$$

---

MCQ No. 148

A heat engine absorbs 6000 J of heat and rejects 4200 J. The useful work obtained is:

a) 1200 J

b) 1500 J

c) 1800 J

d) 2400 J

Correct Answer: c) 1800 J

Explanation:

$$W=Q_H-Q_C$$
$$=6000-4200 =1800\text{ J}$$

---

MCQ No. 149

The efficiency of the engine in MCQ 148 is:

a) 20%

b) 25%

c) 30%

d) 35%

Correct Answer: c) 30%

Explanation:

$$\eta=\frac{1800}{6000}\times100 =30\%$$

---

MCQ No. 150

A Carnot engine has an efficiency of 75%. If the hot reservoir is at 800 K, the cold reservoir temperature is:

a) 100 K

b) 150 K

c) 200 K

d) 250 K

Correct Answer: c) 200 K

Explanation:

$$0.75=1-\frac{T_C}{800}$$
$$T_C=200\text{ K}$$

---

MCQ No. 151

The coefficient of performance of a refrigerator is 6. If it removes 1800 J of heat, the work required is:

a) 200 J

b) 300 J

c) 400 J

d) 600 J

Correct Answer: b) 300 J

Explanation:

$$COP=\frac{Q_L}{W}$$
$$W=\frac{1800}{6}=300\text{ J}$$

---

MCQ No. 152

A refrigerator consumes 500 J of electrical work and has a COP of 4. The heat rejected to the surroundings is:

a) 1500 J

b) 2000 J

c) 2500 J

d) 3000 J

Correct Answer: c) 2500 J

Explanation:

Heat removed,

$$Q_L=4\times500=2000\text{ J}$$

Heat rejected,

$$Q_H=Q_L+W =2000+500 =2500\text{ J}$$

---

MCQ No. 153

One mole of an ideal gas has $C_V=20.8\;J\,mol^{-1}K^{-1}$ . The increase in internal energy for a 40 K rise in temperature is:

a) 416 J

b) 624 J

c) 832 J

d) 1040 J

Correct Answer: c) 832 J

Explanation:

$$\Delta U=nC_V\Delta T$$
$$=1\times20.8\times40 =832\text{ J}$$

---

MCQ No. 154

A gas expands from 1.2 m³ to 1.8 m³ under a constant pressure of 800 Pa. The work done is:

a) 320 J

b) 400 J

c) 480 J

d) 640 J

Correct Answer: c) 480 J

Explanation:

$$W=P\Delta V$$
$$=800(1.8-1.2) =480\text{ J}$$

---

MCQ No. 155

A gas absorbs 500 J of heat during an isothermal expansion. The work done by the gas is:

a) 0 J

b) 250 J

c) 500 J

d) 750 J

Correct Answer: c) 500 J

Explanation:

For an ideal gas in an isothermal process,

$$\Delta U=0$$

Therefore,

$$Q=W$$

---

MCQ No. 156

If $C_P=29.1\;J\,mol^{-1}K^{-1}$  and $R=8.31\;J\,mol^{-1}K^{-1}$ , then $C_V$ equals:

a) 18.5

b) 20.8

c) 22.4

d) 24.5

Correct Answer: b) 20.8

Explanation:

Using Mayer's relation,

$$C_V=C_P-R$$
$$=29.1-8.31 =20.8$$

---

MCQ No. 157

Which process results in the greatest decrease in temperature of an ideal gas?

a) Isothermal expansion

b) Isochoric heating

c) Adiabatic expansion

d) Isobaric heating

Correct Answer: c) Adiabatic expansion

Explanation:

During adiabatic expansion, the gas does work without receiving heat, causing the temperature to decrease significantly.

---

MCQ No. 158

The area enclosed by a cyclic process on a P–V diagram represents the:

a) Heat supplied

b) Change in internal energy

c) Net work done in one complete cycle

d) Entropy change

Correct Answer: c) Net work done in one complete cycle

Explanation:

The enclosed area on a P–V diagram gives the net work done by the system during one complete thermodynamic cycle.

---

MCQ No. 159

For a complete thermodynamic cycle, the change in internal energy is:

a) Positive

b) Negative

c) Zero

d) Equal to heat supplied

Correct Answer: c) Zero

Explanation:

Internal energy is a state function. Since the system returns to its initial state after one complete cycle,

$$\Delta U=0.$$

---

MCQ No. 160

A reversible engine always has ______ efficiency than an irreversible engine operating between the same two temperatures.

a) Lower

b) Equal

c) Higher

d) Zero

Correct Answer: c) Higher

Explanation:

According to Carnot's theorem, no irreversible engine can be more efficient than a reversible engine operating between the same temperature limits.

---

MCQ No. 161

An ideal gas absorbs 1800 J of heat and performs 700 J of work. The increase in its internal energy is:

a) 900 J

b) 1000 J

c) 1100 J

d) 2500 J

Correct Answer: c) 1100 J

Explanation:

According to the First Law of Thermodynamics,

$$\Delta U=Q-W$$
$$\Delta U=1800-700=1100\text{ J}$$

---

MCQ No. 162

A gas loses 500 J of heat while 300 J of work is done on it. The change in internal energy is:

a) –800 J

b) –200 J

c) +200 J

d) +800 J

Correct Answer: b) –200 J

Explanation:

Since heat leaves the system,

$$Q=-500\text{ J}$$

Work is done on the gas,

$$W=-300\text{ J}$$

Therefore,

$$\Delta U=Q-W =(-500)-(-300) =-200\text{ J}$$

---

MCQ No. 163

A gas expands from 0.40 m³ to 0.70 m³ at a constant pressure of $3\times10^5$ . The work done is:

a) 30 kJ

b) 60 kJ

c) 90 kJ

d) 120 kJ

Correct Answer: c) 90 kJ

Explanation:

$$W=P\Delta V$$
$$=(3\times10^5)(0.30) =9\times10^4\text{ J} =90\text{ kJ}$$

---

MCQ No. 164

A gas absorbs 1000 J of heat during an isochoric process. The work done by the gas is:

a) 1000 J

b) 500 J

c) Zero

d) –1000 J

Correct Answer: c) Zero

Explanation:

At constant volume,

$$\Delta V=0$$

Hence,

$$W=P\Delta V=0$$

---

MCQ No. 165

During an isothermal compression of an ideal gas, the internal energy:

a) Increases

b) Decreases

c) Remains constant

d) Doubles

Correct Answer: c) Remains constant

Explanation:

Internal energy of an ideal gas depends only on temperature. Since temperature remains constant in an isothermal process,

$$\Delta U=0.$$

---

MCQ No. 166

A Carnot engine operates between 1000 K and 400 K. Its efficiency is:

a) 40%

b) 50%

c) 60%

d) 70%

Correct Answer: c) 60%

Explanation:

$$\eta=1-\frac{T_C}{T_H}$$
$$=1-\frac{400}{1000} =0.60$$

Efficiency = 60%

---

MCQ No. 167

A heat engine absorbs 5000 J of heat and has an efficiency of 40%. The useful work produced is:

a) 1000 J

b) 1500 J

c) 2000 J

d) 2500 J

Correct Answer: c) 2000 J

Explanation:

$$W=\eta Q_H$$
$$=0.40\times5000 =2000\text{ J}$$

---

MCQ No. 168

A heat engine absorbs 5000 J of heat and produces 2000 J of work. The heat rejected to the sink is:

a) 2000 J

b) 2500 J

c) 3000 J

d) 3500 J

Correct Answer: c) 3000 J

Explanation:

$$Q_C=Q_H-W$$
$$=5000-2000 =3000\text{ J}$$

---

MCQ No. 169

A refrigerator removes 2400 J of heat while consuming 600 J of work. Its coefficient of performance is:

a) 2

b) 3

c) 4

d) 5

Correct Answer: c) 4

Explanation:

$$COP=\frac{Q_L}{W}$$
$$=\frac{2400}{600}=4$$

---

MCQ No. 170

If the COP of a refrigerator is 5 and it removes 2500 J of heat, the work supplied is:

a) 250 J

b) 500 J

c) 750 J

d) 1000 J

Correct Answer: b) 500 J

Explanation:

$$W=\frac{Q_L}{COP}$$
$$=\frac{2500}{5} =500\text{ J}$$

---

MCQ No. 171

One mole of an ideal gas has $C_P=29.1\;J\,mol^{-1}K^{-1}$. The heat required to raise its temperature by 30 K at constant pressure is:

a) 582 J

b) 684 J

c) 873 J

d) 930 J

Correct Answer: c) 873 J

Explanation:

$$Q=nC_P\Delta T$$
$$=1\times29.1\times30 =873\text{ J}$$

---

MCQ No. 172

One mole of an ideal gas has $C_V=20.8\;J\,mol^{-1}K^{-1}$ . The increase in internal energy for a temperature rise of 25 K is:

a) 420 J

b) 520 J

c) 620 J

d) 720 J

Correct Answer: b) 520 J

Explanation:

$$\Delta U=nC_V\Delta T$$
$$=1\times20.8\times25 =520\text{ J}$$

---

MCQ No. 173

The area under the P–V curve during an expansion process represents:

a) Heat absorbed

b) Internal energy

c) Work done by the gas

d) Entropy

Correct Answer: c) Work done by the gas

Explanation:

For any thermodynamic process,

the area under the pressure-volume graph gives the work done.

---

MCQ No. 174

A gas undergoes one complete thermodynamic cycle. The net change in its internal energy is:

a) Positive

b) Negative

c) Zero

d) Equal to the work done

Correct Answer: c) Zero

Explanation:

Internal energy is a state function.

After a complete cycle, the system returns to its original state.

---

MCQ No. 175

Which thermodynamic process has both changing pressure and changing volume while no heat is exchanged?

a) Isothermal

b) Isochoric

c) Isobaric

d) Adiabatic

Correct Answer: d) Adiabatic

Explanation:

In an adiabatic process,

$$Q=0$$

while both pressure and volume usually change.

---

MCQ No. 176

A Carnot engine operates between 500 K and 250 K. Its maximum efficiency is:

a) 25%

b) 40%

c) 50%

d) 75%

Correct Answer: c) 50%

Explanation:

$$\eta=1-\frac{250}{500} =0.50$$

---

MCQ No. 177

Increasing the temperature of the hot reservoir while keeping the cold reservoir constant will:

a) Decrease Carnot efficiency

b) Increase Carnot efficiency

c) Leave efficiency unchanged

d) Make efficiency zero

Correct Answer: b) Increase Carnot efficiency

Explanation:

Since

$$\eta=1-\frac{T_C}{T_H},$$

an increase in $T_H$ increases efficiency.

---

MCQ No. 178

A reversible engine operating between two given temperatures always has:

a) Minimum efficiency

b) Maximum efficiency

c) Zero work output

d) Zero entropy

Correct Answer: b) Maximum efficiency

Explanation:

According to Carnot's theorem, no engine operating between the same temperatures can be more efficient than a reversible engine.

---

MCQ No. 179

A spontaneous process in an isolated system is accompanied by:

a) Decrease in entropy

b) Constant entropy

c) Increase in entropy

d) Zero internal energy

Correct Answer: c) Increase in entropy

Explanation:

The entropy of an isolated system increases during spontaneous natural processes.

---

MCQ No. 180

Which statement correctly distinguishes the First and Second Laws of Thermodynamics?

a) The First Law determines the direction of heat flow, while the Second Law states that energy is conserved.

b) The First Law states that energy is conserved, while the Second Law determines the direction of natural processes and limits heat engine efficiency.

c) Both laws describe only ideal gases.

d) Both laws state that entropy remains constant.

Correct Answer: b) The First Law states that energy is conserved, while the Second Law determines the direction of natural processes and limits heat engine efficiency.

Explanation:

The First Law of Thermodynamics is the law of conservation of energy, expressing the relationship between heat, work, and internal energy. The Second Law of Thermodynamics establishes the natural direction of heat flow, introduces the concept of entropy, and explains why no heat engine can achieve 100% efficiency.

---

MCQ No. 181

An ideal gas receives 2400 J of heat and performs 900 J of work. The increase in its internal energy is:

a) 1200 J

b) 1500 J

c) 2400 J

d) 3300 J

Correct Answer: b) 1500 J

Explanation:

Using the First Law of Thermodynamics,

$$\Delta U = Q - W$$
$$=2400-900=1500\text{ J}$$

---

MCQ No. 182

A gas rejects 700 J of heat while 400 J of work is done on it. The change in internal energy is:

a) –300 J

b) –1100 J

c) +300 J

d) +1100 J

Correct Answer: a) –300 J

Explanation:

Since heat is rejected,

$$Q=-700\text{ J}$$

Work done on the gas,

$$W=-400\text{ J}$$

Therefore,

$$\Delta U=Q-W =(-700)-(-400) =-300\text{ J}$$

---

MCQ No. 183

A gas expands from 0.25 m³ to 0.45 m³ against a constant pressure of $2.5\times10^5$ Pa. The work done is:

a) 20 kJ

b) 40 kJ

c) 50 kJ

d) 60 kJ

Correct Answer: c) 50 kJ

Explanation:

$$W=P\Delta V$$
$$=(2.5\times10^5)(0.20) =5.0\times10^4\text{ J} =50\text{ kJ}$$

---

MCQ No. 184

A gas undergoes an adiabatic compression. Which quantity remains constant?

a) Temperature

b) Pressure

c) Heat exchanged

d) Volume

Correct Answer: c) Heat exchanged

Explanation:

In an adiabatic process,

$$Q=0$$

No heat is exchanged with the surroundings.

---

MCQ No. 185

A heat engine absorbs 8000 J of heat and rejects 5000 J. The efficiency of the engine is:

a) 25%

b) 37.5%

c) 40%

d) 62.5%

Correct Answer: b) 37.5%

Explanation:

Work done,

$$W=8000-5000=3000\text{ J}$$

Efficiency,

$$\eta=\frac{3000}{8000}\times100 =37.5\%$$

---

MCQ No. 186

A Carnot engine operates between 750 K and 300 K. Its maximum efficiency is:

a) 40%

b) 50%

c) 60%

d) 70%

Correct Answer: c) 60%

Explanation:

$$\eta=1-\frac{300}{750} =0.60$$

---

MCQ No. 187

A refrigerator has a COP of 6. If the work supplied is 400 J, the heat extracted from the cold reservoir is:

a) 1600 J

b) 2000 J

c) 2400 J

d) 2800 J

Correct Answer: c) 2400 J

Explanation:

$$Q_L=COP\times W$$
$$=6\times400 =2400\text{ J}$$

---

MCQ No. 188

The heat rejected by the refrigerator in MCQ No. 187 is:

a) 2400 J

b) 2600 J

c) 2800 J

d) 3000 J

Correct Answer: c) 2800 J

Explanation:

$$Q_H=Q_L+W$$
$$=2400+400 =2800\text{ J}$$

---

MCQ No. 189

One mole of an ideal gas is heated at constant pressure through 40 K. If $C_P=29.1\,J\,mol^{-1}K^{-1}$ , the heat supplied is:

a) 873 J

b) 960 J

c) 1164 J

d) 1240 J

Correct Answer: c) 1164 J

Explanation:

$$Q=nC_P\Delta T$$
$$=1\times29.1\times40 =1164\text{ J}$$

---

MCQ No. 190

One mole of an ideal gas has $C_V=20.8\,J\,mol^{-1}K^{-1}$ . The increase in internal energy for a temperature rise of 50 K is:

a) 840 J

b) 960 J

c) 1040 J

d) 1164 J

Correct Answer: c) 1040 J

Explanation:

$$\Delta U=nC_V\Delta T$$
$$=1\times20.8\times50 =1040\text{ J}$$

---

MCQ No. 191

The efficiency of a Carnot engine depends only upon:

a) Nature of the working substance

b) Pressure inside the cylinder

c) Temperatures of the hot and cold reservoirs

d) Size of the engine

Correct Answer: c) Temperatures of the hot and cold reservoirs

Explanation:

The efficiency of a Carnot engine is

$$\eta=1-\frac{T_C}{T_H}$$

which depends only on the reservoir temperatures.

---

MCQ No. 192

For a complete thermodynamic cycle, which statement is correct?

a) Heat supplied equals zero.

b) Work done equals zero.

c) Net change in internal energy is zero.

d) Pressure remains constant.

Correct Answer: c) Net change in internal energy is zero.

Explanation:

Since internal energy is a state function, it returns to its initial value after one complete cycle.

---

MCQ No. 193

The area enclosed by a cyclic process on a P–V diagram gives the:

a) Heat supplied

b) Pressure change

c) Net work done during the cycle

d) Internal energy

Correct Answer: c) Net work done during the cycle

Explanation:

The enclosed area on the P–V graph represents the net work performed in one complete cycle.

---

MCQ No. 194

Which thermodynamic process is represented by a vertical line on a P–V diagram?

a) Isothermal

b) Isobaric

c) Isochoric

d) Adiabatic

Correct Answer: c) Isochoric

Explanation:

A vertical line indicates constant volume.

---

MCQ No. 195

The ratio $\gamma=\frac{C_P}{C_V}$ for a diatomic ideal gas is approximately:

a) 1.20

b) 1.33

c) 1.40

d) 1.67

Correct Answer: c) 1.40

Explanation:

For most diatomic gases at ordinary temperatures,

$$\gamma=\frac75\approx1.40$$

---

MCQ No. 196

The SI unit of entropy is:

a) J

b) J K⁻¹

c) J kg⁻¹

d) W K⁻¹

Correct Answer: b) J K⁻¹

Explanation:

Entropy is measured in joules per kelvin.

---

MCQ No. 197

If the temperatures of the hot and cold reservoirs become equal, the efficiency of a Carnot engine becomes:

a) 25%

b) 50%

c) 75%

d) Zero

Correct Answer: d) Zero

Explanation:

If

$$T_H=T_C,$$

then

$$\eta=1-\frac{T_C}{T_H}=0$$

No useful work can be produced.

---

MCQ No. 198

Which process is most nearly reversible?

a) Sudden free expansion of a gas

b) Explosion inside a cylinder

c) Infinitely slow isothermal expansion

d) Frictional compression

Correct Answer: c) Infinitely slow isothermal expansion

Explanation:

A process carried out infinitely slowly through a series of equilibrium states closely approximates a reversible process.

---

MCQ No. 199

According to the Second Law of Thermodynamics, the entropy of the universe during a spontaneous process:

a) Decreases

b) Remains constant

c) Increases

d) Becomes zero

Correct Answer: c) Increases

Explanation:

The total entropy of the universe always increases during a spontaneous natural process.

---

MCQ No. 200

Which one of the following statements is correct regarding the First and Second Laws of Thermodynamics?

a) The First Law limits engine efficiency, while the Second Law states that energy is conserved.

b) The First Law establishes conservation of energy, whereas the Second Law determines the direction of natural processes and explains why no heat engine can be 100% efficient.

c) Both laws describe only reversible processes.

d) Both laws state that entropy remains constant.

Correct Answer: b) The First Law establishes conservation of energy, whereas the Second Law determines the direction of natural processes and explains why no heat engine can be 100% efficient.

Explanation:

The First Law of Thermodynamics relates heat, work, and internal energy through the conservation of energy. The Second Law introduces entropy, determines the direction of spontaneous processes, and establishes the theoretical limit on the efficiency of heat engines.

---

📚 Continue Your Physics Preparation

If you found this quiz helpful, explore our complete collection of Physics learning resources.

🔬 Physics MCQs Hub

---

More Study Resources for Students and Teachers

• Computer Science 11th Class Notes (Main Page) 
• Computer Science 12th Class Notes (Main Page) 

************************************

1. English Poems Analysis Hub– A to Z Index (English Poetry) 

(https://poemanalysishub.blogspot.com/p/english-poems-analysis-to-z-index.html)

2. Website for School and College Level Mathematics  

(https://askraremaths.blogspot.com)

3. ASK Rare Class Notes – Study Resources for Students & Teachers 

(https://askrareclassnotes.blogspot.com/)

© 2026 & onwards Academic Skills and Knowledge (ASK)   

Note:  Write me in the comments box below for any query and also Share this information with your classmates and friends.

---

© https://askrareclassnotes.blogspot.com | Learn • Practice • Succeed

---

Best Tools and Supplies for Students and Teachers:

📚 Grammar Books – Improve Writing, Score Higher
🪑 Study Chairs – Sit Comfortably, Study Better
🛋️ Study Desks – Organized Space, Better Learning
💡 Desk Lamps – Bright Light, Better Focus
⌚ Digital Watches– Manage Time, Improve Results
📱 Phone Stands – Hands-Free Learning Made Easy
🎧 Headphones – Focus Better, Learn Without Distractions
⌨️ Wireless Keyboards – Type Faster, Work Smarter
🖱️ Wireless Mouse – Smooth Control, Better Workflow
🖨️ Printers – Print Smart, Save Time

Disclosure: The above links on this page are affiliate links. This means that if you make a purchase through them, I may earn a small commission at no additional cost to you. Your support helps me maintain, improve, and continue providing valuable free content on this website.

With Best Regards

ASKRare Team

---

---

🌍📖

"Knowledge grows when it is shared."

At ASK Rare Class Notes, we believe quality education should be freely accessible to everyone. Learn, share, inspire, and help others succeed.