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ISC physics students often prepare for the theory paper and treat the practical as an afterthought. That is an expensive habit: 30 of the 100 marks sit outside the theory paper, and the practical has its own rules about recording readings and drawing graphs. This post sets out how the Council for the Indian School Certificate Examinations (CISCE) structures the ISC 2027 physics marks, which theory units weigh most, and what examiners look for in the practical.
How are ISC 2027 physics marks divided?
The CISCE syllabus for ISC Examination Year 2027, Physics (861) gives Class XII two papers:
Paper I, Theory: 3 hours, 70 marks.
Paper II, Practical: 3 hours, 15 marks.
Project Work: 10 marks.
Practical File: 5 marks.
That adds up to 70 + 15 + 10 + 5 = 100. Class XI uses the same split. CISCE revises syllabuses by examination year, so check the document for your own year on the CISCE website before you plan.
Which theory units carry the most marks?
The syllabus groups the nine Class XII units into weightage bands that total 70:
Electrostatics and Current Electricity together: 14 marks.
Magnetic Effects of Current and Magnetism, with Electromagnetic Induction and Alternating Currents: 16 marks.
Electromagnetic Waves: 2 marks.
Optics: 18 marks.
Dual Nature of Radiation and Matter: 7 marks.
Atoms and Nuclei: 6 marks.
Electronic Devices: 7 marks.
Check: 14 + 16 + 2 + 18 + 7 + 6 + 7 = 70. Optics on its own is about a quarter of the theory paper, and the electricity and magnetism bands together make 30. The syllabus also notes that numerical problems are included from all topics unless a topic is marked qualitative, so practise numericals across the whole list, not only in electricity.
What does the practical paper test?
CISCE says the experiments for the practical exam come mostly from two groups: ray optics and current electricity. In optics, "the main skill required" is removing parallax between a needle and the real image of another needle. In electricity, it is making connections "strictly following the given diagram", with attention to polarity, meter ranges, zero error and least count.
The required list includes, among others, the focal length of a convex lens by the u-v method, refractive index of a liquid using a convex lens and plane mirror, a metre bridge to find the resistance and specific resistance of a wire, verifying Ohm's law with a graph, and finding the internal resistance of a cell with a potentiometer. Students are expected to have completed all experiments on the list. Short-answer questions may also be set on the theory behind each experiment.
How are practical graphs judged?
The syllabus states there will be one graph in the practical paper and lists its rules. The ones students most often break:
Use at least 60% of the graph paper along both axes, with a uniform, convenient scale (avoid one small division = 0.33 or 0.67).
Mark points with a circled dot or a circled cross; "a blob" counts as a misplot.
Draw a thin best-fit straight line, which need not pass through every point or through the origin.
Find the slope from two distant points on the line, using more than half its length, and not from your plotted points.
Read intercepts carefully, with the origin at (0, 0) when intercepts are needed.
Worked example: slope in the Ohm's law experiment
Experiment 9 asks you to verify Ohm's law for a 60 cm constantan wire and find resistance per cm from the slope of a potential difference against current graph. Suppose (sample numbers) your best-fit line passes through two points that you read off the line, not from your data: (0.10 A, 0.42 V) and (0.50 A, 2.10 V).
Slope = (2.10 - 0.42) / (0.50 - 0.10) = 1.68 / 0.40 = 4.2 V/A, so R = 4.2 ohm.
Resistance per cm = 4.2 / 60 = 0.07 ohm per cm.
Write the slope to the decimal places or significant figures the question asks for. A common mistake is to use the first and last plotted readings, which ties the slope to two noisy points instead of the whole line. Our guide to reading physics graphs has more practice on slopes and intercepts.
How are the project and file assessed?
Both are assessed by a Visiting Examiner appointed locally and approved by CISCE. You do one project, which can be theoretical, a working model or an investigatory experiment done under a teacher's supervision. The report needs a title, abstract, theory, set-up, observations with tables, graphs if any, analysis, and conclusion, and the teacher should approve the draft. The 5-mark file is judged on the practical record you kept through the year, so keep it up to date rather than writing it in the final week. Our post on board practical exams and the viva has tips for the oral part.
Does ISC count for entrance exams?
Yes. The NEET (UG) 2026 bulletin names "the Indian School Certificate Examination" as an accepted Class 12 qualification, and the IIST 2026 brochure lists CISCE among recognised boards. Each still sets its own marks and subject rules, so read them separately.
A practice routine for the term
Weekly, theory: one timed set of mixed numericals from two units, weighted towards Optics and the electricity and magnetism bands.
Weekly, practical: redo one experiment's graph from old readings, applying every rule above, and compute the slope from two distant line points.
Monthly: explain the theory of two experiments aloud in five minutes each, as you would in a viva.
Ongoing: write up each experiment in your file the same week you perform it.
If lens images or field patterns are hard to picture from the textbook, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read.
This week, take your last practical graph and check it against the six graph rules; fix the first one it breaks.
