Thermodynamics is a core and high-weightage chapter in Class 11 Physics that explains the relationship between heat, work, energy, and temperature. This chapter covers important topics such as thermal equilibrium, zeroth law of thermodynamics, first law of thermodynamics, internal energy, work done in thermodynamic processes, specific heat capacities, isothermal and adiabatic processes, and second law of thermodynamics. These concepts are fundamental for Class 11 exams and competitive exams like JEE and NEET.
NCERT Solutions for Class 11 Physics Chapter 11 – Thermodynamics are prepared strictly according to the latest CBSE syllabus and exam pattern. The solutions are written in simple, step-by-step language with clear derivations, PV diagrams, and solved numericals, helping students build strong conceptual clarity and score well in school examinations.
NCERT Solutions for Class 11 Physics Chapter 11 – Thermodynamics
Q.
A geyser heats water flowing at the rate of 3.0 litres per minute from 27°C to 77°C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0 × 104 Jg-1?
Q.
What amount of heat must be supplied to 2.0 × 10–2 kg of nitrogen (at room temperature) to raise its temperature by 45°C at constant pressure? (Molecular mass of N2 = 28; R = 8.3 J mol–1 K–1.)
Q.
Explain why
(a) Two bodies at different temperatures T1 and T2 if brought in thermal contact do not necessarily settle to the mean temperature (T1 + T2)/2.
(b) The coolant in a chemical or a nuclear plant (i.e., the liquid used to prevent the different parts of a plant from getting too hot) should have high specific heat.
(c) Air pressure in a car tyre increases during driving.
(d) The climate of a harbour town is more temperate than that of a town in a desert at the same latitude.
Q.
A cylinder with a movable piston contains 3 moles of hydrogen at standard temperature and pressure. The walls of the cylinder are made of a heat insulator, and the piston is insulated by having a pile of sand on it. By what factor does the pressure of the gas increase if the gas is compressed to half its original volume?
Q.
In changing the state of a gas adiabatically from an equilibrium state A to another equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in the latter case?
(Take 1 cal = 4.19 J)
Q.
Two cylinders A and B of equal capacity are connected to each other via a stopcock.
A contains a gas at standard temperature and pressure. B is completely evacuated.
The entire system is thermally insulated. The stopcock is suddenly opened. Answer the following:
(a) What is the final pressure of the gas in A and B?
(b) What is the change in internal energy of the gas?
(c) What is the change in the temperature of the gas?
(d) Do the intermediate states of the system (before settling to the final equilibrium state) lie on its P-V-T surface?
Q.
A steam engine delivers 5.4 × 108 J of work per minute and services 3.6 × 109 J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?
Q.
An electric heater supplies heat to a system at a rate of 100 W. If system performs work at a rate of 75 Joules per second. At what rate is the internal energy increasing?
Q.
A thermodynamic system is taken from an original state to an intermediate state by the linear process shown in Fig. (12.13)
Its volume is then reduced to the original value from E to F by an isobaric process.
Calculate the total work done by the gas from D to E to F
Q.
A refrigerator is to maintain eatables kept inside at 9°C. If room temperature is 36°C, calculate the coefficient of performance.
Q.
Zeroth law of thermodynamics represents:
a) Concept of temperature
b) State of thermal equilibrium of a system
c) The idea that heat is a form of energy
Q.1) Explain why:
(a) Two bodies at different temperatures T1 and T2, if brought in thermal contact, do not necessarily settle to the mean temperature (T1 + T2)/2.
When two bodies at different temperatures are brought in thermal contact, heat flows from the body at higher temperature to the body at lower temperature until thermal equilibrium is reached.
The final equilibrium temperature depends on the thermal capacities of the two bodies.
Only if both bodies have the same thermal capacity will the final temperature be equal to the mean temperature.
(b) The coolant in a chemical or nuclear plant should have high specific heat.
The heat-absorbing capacity of a substance is directly proportional to its specific heat.
A coolant with high specific heat can absorb a large amount of heat with only a small rise in temperature.
Therefore, the coolant used in chemical or nuclear plants should have high specific heat.
(c) Air pressure in a car tyre increases during driving.
During driving, the motion of air molecules inside the tyre increases due to friction and heating.
This increases the temperature of the air inside the tyre.
According to Gay-Lussac’s law, at constant volume, pressure is directly proportional to temperature.
Hence, an increase in temperature leads to an increase in pressure inside the tyre.
(d) The climate of a harbour town is more temperate than that of a desert town at the same latitude.
Harbour towns have higher relative humidity due to the presence of large water bodies.
Water has a high specific heat and moderates temperature changes.
Therefore, harbour towns experience a more temperate climate compared to desert towns at the same latitude.
Q.2) Two cylinders A and B of equal capacity are connected by a stopcock.
Cylinder A contains a gas at standard temperature and pressure, while cylinder B is completely evacuated.
The system is thermally insulated and the stopcock is suddenly opened.
(a) What is the final pressure of the gas in A and B?
When the stopcock is opened, the volume available to the gas becomes double.
According to Boyle’s law, at constant temperature, pressure is inversely proportional to volume.
Hence, the pressure becomes half of its original value.
Since the initial pressure was 1 atm, the final pressure in each cylinder is 0.5 atm.
(b) What is the change in internal energy of the gas?
No work is done by or on the gas and no heat is exchanged with the surroundings.
Therefore, the internal energy of the gas remains unchanged.
(c) What is the change in the temperature of the gas?
Since the internal energy of the gas does not change, the temperature of the gas also remains unchanged.
(d) Do the intermediate states of the system lie on its P–V–T surface?
The expansion of gas is free and rapid and hence not quasi-static.
The intermediate states are non-equilibrium states and do not satisfy the ideal gas equation.
Therefore, the intermediate states do not lie on the P–V–T surface.
Q.3) Zeroth law of thermodynamics represents:
(a) Concept of temperature
(b) State of thermal equilibrium of a system
(c) The idea that heat is a form of energy
Answer:
Only options (a) and (b) are correct.
Note: Q&A containing MathML or LaTeX/Katex code cannot be rendered in PDF documents.
FAQs: Class 11 Physics Chapter 11 – Thermodynamics
Q1. Is Thermodynamics important for exams?
Yes, it is a high-weightage and foundational chapter for Physics.
Q2. Which topics are most important in this chapter?
First law of thermodynamics, thermodynamic processes, and second law.
Q3. Are numericals asked from this chapter?
Yes, process-based and work–heat numericals are very common.
Q4. Are diagrams important here?
Yes, PV diagrams are frequently asked in exams.
Q5. How do NCERT Solutions help?
They provide NCERT-aligned, exam-ready explanations with solved numericals.