CBSE Physics 042 in 2026-27: Paper Pattern, Marks Map and Problem-Solving Toolkit
This chapter sets out the verified shape of the 2026-27 Class XII Physics theory paper, the marks carried by each block of units, and the working toolkit that every later chapter relies on: the printed constants, hand-calculation habits, units and dimensions, sign conventions and the practical scheme. Knowing how marks are distributed and how each question type is built lets you spend revision time where the paper rewards it.
KarmSakha preparation topics covered
- Theory paper design: 70 marks, 3 hours, 33 questions
- Section-wise marks and internal choice
- Marks by unit block and the typology split
- Assertion-reasoning, case-study, short and long-answer methods
- Constants printed on the question paper
- Powers-of-ten estimation and hand calculation
- Units and dimensions of Class XII quantities
- Cartesian sign convention and circuit sign rules
- Practical scheme and experiment list
The 2026-27 theory paper: 70 marks, 3 hours, 33 questions
The Class XII Physics theory paper (Subject Code 042) carries 70 marks and runs for 3 hours. The practical examination adds 30 marks, so the gross total is 100. The sample question paper issued by CBSE for the 2026-27 session shows the structure this book assumes: 33 questions in five sections lettered A to E, all of them compulsory. There is no overall choice, so no section or unit can be dropped. The only flexibility is an internal choice inside a few questions, where two alternatives are printed and you attempt one. A footnote on the sample paper states that the question paper design and assessment pattern is unchanged for the 2026-27 session.
The arithmetic of the sections is worth knowing cold. Section A has 16 questions of 1 mark, of which twelve are multiple-choice and four are assertion-reasoning; Section B has 5 questions of 2 marks; Section C has 7 questions of 3 marks; Section D has 2 case-study questions of 4 marks each; and Section E has 3 long-answer questions of 5 marks each. The totals are 16 + 10 + 21 + 8 + 15 = 70, over 16 + 5 + 7 + 2 + 3 = 33 questions. Section C is therefore the heaviest block at 21 marks, and the twelve questions of Sections C, D and E together carry 44 of the 70 marks.
Internal choice is concentrated where the marks are. The instructions place it in two of the five questions of Section B, one of the seven questions of Section C, and all three questions of Section E, which puts 4 + 3 + 15 = 22 marks in questions that print an alternative. In the sample paper the Section B alternatives are different topics (classifying a magnetic material versus stating Gauss's law of magnetism), so the choice is of content, not of wording. Use of calculators is not allowed.
Sub-parts matter for how you spend time. In the sample paper each case study is split into four sub-parts of 1 mark, mixing multiple-choice parts with short written answers; the 5-mark answers are split as 2 + 2 + 1 or 3 + 2, and a 3-mark item can be split as 2 + 1. With 180 minutes for 70 marks the average is about 2.6 minutes per mark. That is arithmetic, not a CBSE rule, but it suggests roughly 13 minutes for a 5-mark answer and well under 3 for a 1-mark item.
The sample paper shows the pattern, not the exact questions or the placement of choices, and the board paper may vary within the stated design; check the latest CBSE circulars before the examination. Content that NCERT marks as excluded for the session is not tested.
| Section | Question type | Questions | Marks each | Section total | Internal choice (per sample paper) |
|---|---|---|---|---|---|
| A | 12 MCQ + 4 assertion-reasoning | 16 | 1 | 16 | None |
| B | Short answer | 5 | 2 | 10 | Two questions |
| C | Short answer | 7 | 3 | 21 | One question |
| D | Case study | 2 | 4 | 8 | None |
| E | Long answer | 3 | 5 | 15 | All three questions |
| Total | 33 | 70 | 22 marks sit in questions with a choice |
Marks by unit and where each unit sits in this book
CBSE prints the theory marks against merged blocks of units, not against single units. Units I and II (Electrostatics and Current Electricity) together carry 16 marks. Units III and IV (Magnetic Effects of Current and Magnetism, and Electromagnetic Induction and Alternating Currents) carry 17. Units V and VI (Electromagnetic Waves and Optics) carry 18. Units VII and VIII (Dual Nature of Radiation and Matter, and Atoms and Nuclei) carry 12. Unit IX (Electronic Devices) carries 7. The five blocks sum to 70. A statement such as 'Current Electricity is worth 7 marks' is therefore not supported by the curriculum; only the block totals are.
The NCERT Class XII books have 14 chapters, and this book regroups them into 12 revision chapters. The table below maps each mark block to the NCERT chapters it contains and to the chapters of this book. Two regroupings need attention. Electromagnetic waves are taught in Chapter 7 of this book together with alternating current, so Chapter 7 straddles the 17-mark and 18-mark blocks. Atoms and Nuclei, two NCERT chapters, are one chapter here (Chapter 11). Chapter 1, which you are reading, teaches how to sit the paper and does not itself carry marks.
The paper is also designed by competency. The curriculum splits the 70 theory marks as Remembering and Understanding 27 marks, Applying 22 marks, and Analysing, Evaluating and Creating 21 marks. CBSE rounds these shares to about 38%, 32% and 30%; the exact ratios are 38.6%, 31.4% and 30.0%. The consequence is that 22 + 21 = 43 of the 70 marks, about 61%, ask for more than recall: choosing a law, combining two results, reading a graph or judging which of two explanations is valid. A formula sheet alone covers the first block; the remaining two blocks reward knowing the condition under which each formula holds, which is why every formula in this book carries its condition.
- Remembering and Understanding: 27 marks (about 38%)
- Applying: 22 marks (about 32%)
- Analysing, Evaluating and Creating: 21 marks (30%)
| Mark block | Units | NCERT chapters | Marks | Chapters in this book |
|---|---|---|---|---|
| I-II | Electrostatics; Current Electricity | 1, 2, 3 | 16 | 2, 3, 4 |
| III-IV | Magnetic Effects of Current and Magnetism; Electromagnetic Induction and Alternating Currents | 4, 5, 6, 7 | 17 | 5, 6, 7 (alternating current part) |
| V-VI | Electromagnetic Waves; Optics | 8, 9, 10 | 18 | 7 (electromagnetic waves part), 8, 9 |
| VII-VIII | Dual Nature of Radiation and Matter; Atoms and Nuclei | 11, 12, 13 | 12 | 10, 11 |
| IX | Electronic Devices | 14 | 7 | 12 |
| Total | 70 |
How to attack each question type
Assertion-reasoning items in the sample paper use four fixed options: (A) both statements are true and Reason is the correct explanation of Assertion; (B) both are true but Reason is not the correct explanation; (C) Assertion is true but Reason is false; (D) both are false. Judge the two statements separately first, as if they were two independent true-or-false questions. Only if both are true do you ask the third question: does the Reason name the cause or mechanism that makes the Assertion true? Note what the four options leave out. The case 'Assertion false, Reason true' does not appear in the sample paper's list, so when you find it, re-read the Assertion for a missed condition before accepting it.
The commonest trap is a true Reason that is attached to a true Assertion but does not cause it. For example: Assertion, the refractive index of glass is greater than that of air; Reason, light travels at 3 × 10⁸ m/s in vacuum. Both are true, yet the speed in vacuum says nothing about why glass is optically denser, so the answer is B. A second trap is a Reason that is the right idea applied in the wrong direction, such as the fringe width being directly proportional to slit separation. When the Reason contains a proportionality, check each power and each direction before you decide it is true.
Case-study items give a passage and then four 1-mark sub-parts, some multiple-choice and some needing a one- or two-line written answer. Read the sub-parts first, then scan the passage only for the numbers and the named device. Where a sub-part needs a calculation, such as the photon energy in the photoelectric case study of the sample paper, the passage supplies a frequency or wavelength and the constants come from the list printed on the paper.
For 2- and 3-mark 'explain' and 'derive' items, build the answer as a short chain: state the law or definition that applies, write the relation with the condition under which it holds, apply it to the situation in the question, and end with a statement that answers the exact word asked, whether 'why', 'compare' or 'find'. When a 3-mark item has parts I and II, with marks split such as 2 + 1, write each part under its own label.
For 5-mark long answers, the printed choice means two alternatives, and the marks are split across parts, for instance 2 + 2 + 1 or 3 + 2. A derivation is awarded stepwise: the starting law, the geometry or circuit, the key intermediate result and the final expression. If the question mixes a derivation with a numerical, finish the derivation first and then use its final expression for the numerical, and give units with every numerical answer.
| Assertion true? | Reason true? | Reason explains Assertion? | Option to choose |
|---|---|---|---|
| Yes | Yes | Yes | A |
| Yes | Yes | No | B |
| Yes | No | Not applicable | C |
| No | No | Not applicable | D |
| No | Yes | Not applicable | Not among the four options; recheck the Assertion |
Constants, approximations and hand calculation
Because calculators are not allowed, every numerical in the paper is built to be finished by hand with the constants printed on the question paper. The sample paper lists nine: the speed of light c = 3 × 10⁸ m/s; electron mass 9.1 × 10⁻³¹ kg; proton mass 1.7 × 10⁻²⁷ kg; electronic charge e = 1.6 × 10⁻¹⁹ C; permeability μ₀ = 4π × 10⁻⁷ T m A⁻¹; Planck's constant h = 6.63 × 10⁻³⁴ J s; permittivity ε₀ = 8.854 × 10⁻¹² C² N⁻¹ m⁻²; Avogadro's number 6.023 × 10²³ per gram mole; and the radius of a nucleus of about 10⁻¹⁵ m. This book's numericals use these values unless a question states a different rounded figure, such as hc ≈ 1240 eV nm in the modern-physics chapters; quote the values when you substitute.
Derived constants are what save time. From ε₀ and π = 22/7, 1/(4πε₀) comes to about 9 × 10⁹ N m² C⁻², the value used in Coulomb-law questions, and 1/(4πε₀) is not printed on the paper, so recompute or recall it. From μ₀ = 4π × 10⁻⁷ the combination μ₀/(4π) = 10⁻⁷ T m A⁻¹ removes π entirely from Biot-Savart and Ampere problems. The product hc = 6.63 × 10⁻³⁴ × 3 × 10⁸ J m divided by e gives about 1243 eV nm, so a photon wavelength in nanometres is 1243 divided by its energy in eV. The CODATA 2022 value is 1239.84 eV nm; the roughly 0.3% difference comes only from the rounded values of h, c and e on the paper.
The paper's constants are rounded, and they differ slightly from the exact modern values. CODATA 2022 gives h = 6.62607015 × 10⁻³⁴ J s and e = 1.602176634 × 10⁻¹⁹ C as exact numbers, c = 299 792 458 m/s exactly, ε₀ = 8.8541878188 × 10⁻¹² and μ₀ = 1.25663706127 × 10⁻⁶ in SI units. An answer computed with the printed values will differ from one computed with CODATA values in the third significant figure. Marking follows the data and constants the question supplies, so use the printed ones and do not 'improve' them with remembered values.
Powers-of-ten estimation keeps hand calculation safe. Multiply the numbers and add the exponents separately: (a × 10ᵐ)(b × 10ⁿ) = ab × 10ᵐ⁺ⁿ, and for division subtract the exponents. Round awkward factors to a convenient neighbour and note the direction of the rounding. Keep π as 22/7 when a denominator contains 7 or 14, and 3.14 otherwise. Compare the order of magnitude of the answer with a physical expectation, such as an atomic radius near 10⁻¹⁰ m, before writing the result.
Conversions that recur across the book: 1 eV = 1.6 × 10⁻¹⁹ J with the printed e; 1 u = 931.5 MeV/c² for nuclear problems (NCERT value); 1 kilowatt-hour = 3.6 × 10⁶ J. Write prefixes as powers of ten before substituting: μ = 10⁻⁶, n = 10⁻⁹, p = 10⁻¹². Slips with these three account for most unit errors in capacitance, wavelength and charge problems.
