Class 12 Physics Second law of thermodynamics Notes and Important Questions
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Notes for Class 12 Second law of thermodynamics (Physics) are shown above.
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Important Questions
If efficiency of petrol engine is η₁, and that of diesel engine is η₂, then, which of the following expression is correct?
The efficiency of Carnot engine operating between steam point and ice point is
26.8%
50%
73.2%
100%
Given figure represents the block diagram of a heat engine. What is the efficiency of this engine?
25%
50%
60%
75%
What is meant by entropy? Write the first law of thermodynamics in terms of entropy.
Can a room be cooled by leaving the door of an electric refrigerator open? Justify.
A quantity of monoatomic gas at 30°C is compressed suddenly to (8/27)th parts of its initial volume. Find the change in temperature assuming γ = Cp/Cv = 5/3.
What is the significance of the Clausius statement of the second law of thermodynamics?
Defines the maximum theoretical efficiency of a heat engine.
States that heat cannot spontaneously flow from a colder object to a hotter object.
Describes the relationship between entropy and the reversibility of a process.
Describes the direction of spontaneous change in an isolated system.
A Carnot engine is working between 300K and 600K and has output 200J. What is the energy supplied to the engine?
400 J
800 J
1200 J
1600 J
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Exam
Past Question Analysis
Historical exam-pattern data from past NEB question papers — not a prediction of future questions.
7
Question Items
4
Total Marks
4
Papers Appeared In
| Year | Question Items | Marks |
|---|---|---|
| 2083 | 2 | 1 |
| 2082 | 2 | 1 |
| 2081 | 1 | 1 |
| 2080 | 2 | 1 |
Also appears in 3 model questions (not counted above — model sets aren't actual NEB exam history).
This chapter introduces the principles governing the direction of heat flow and energy conversion. It includes heat engines, refrigerators, Carnot, Otto and Diesel cycles, efficiency and the concept of entropy.
This page covers Second law of thermodynamics, chapter 5 of 25 in the Class 12 Physics syllabus set by the National Examination Board (NEB). 8 important questions for this chapter are available, each with a full solution.
For numerical and derivation-based chapters like this one, working through past NEB questions is usually more useful than re-reading notes alone — try solving each important question above before checking the solution, then compare your working step by step.