CBSE Class 12 Physics 2027: Numericals, Derivations and the 30 Practical Marks

Key Takeaways

• Physics is 70 marks theory plus 30 marks practical. Preparing the 30 practical marks properly is one of the most reliable ways to protect your total.
• Numericals earn marks for method as well as the answer. Write formula, substitution, calculation and unit on every line, even when the arithmetic is easy.
• Keep a short list of derivations and diagrams and test yourself on them weekly with a blank sheet, not by re-reading.
• The paper style reported for 2026-27 has about 50 percent competency-based questions, 20 percent MCQs and 30 percent short and long answers. Check the current sample paper before you finalise your practice sets.
• The date sheet is not out yet (expected around November-December 2026). Plan around your school's pre-board schedule for now.

What the Physics Paper Rewards

Physics at board level is a subject where marks depend on steps. A student who knows the concept but writes only the final answer to a three-mark numerical is handing marks back. The reverse is also true: a student who writes a neat, complete chain of reasoning to a wrong final value will usually still collect a good share of the marks. Boards are marked against a scheme that awards credit for the correct formula, the correct substitution and the correct answer with its unit. If you want to see why this differs from an entrance exam, our guide on how board and competitive exams test different skills is worth ten minutes.

We are deliberately not giving chapter-wise mark weightage here. Weightage is published by CBSE in the curriculum document and reflected in the sample paper, and it can shift between sessions. Use the current sample paper and the latest curriculum document as your source of truth, and do not trust a number you cannot trace to one of them.

Numericals: How to Practise Them

Numericals are the most improvable part of the Physics paper, because the errors are so consistent. Most lost marks come from a small set of causes: a wrong unit conversion, a sign error, using the wrong form of a formula, or stopping one step short. A useful way to practise is to work numericals in three passes.

• First pass, no timer. Solve five or six numericals from one chapter and write full solutions. The goal is accuracy and a clean layout, not speed.
• Second pass, timed. Give yourself roughly the time a mark deserves in the paper (a two-mark numerical should not take ten minutes). Note which ones you could not finish in time and why.
• Third pass, error log. Write each mistake in one line: forgot to convert cm to m, used the wrong sign for the image distance, mixed up peak and rms values. Re-read the log before every mock.

Where should numerical practice concentrate? Roughly, on the areas where calculation is unavoidable: electrostatics and capacitors, current electricity, magnetic effects and electromagnetic induction, alternating current, ray optics and wave optics, dual nature and atomic and nuclear physics. Semiconductor electronics is often more about circuits, diode behaviour and reading graphs than heavy calculation. Confirm which chapters and topics are in the current syllabus for 2026-27 and which portions have been removed before you spend hours on a topic.

Presentation habits that pay off

• Write the given quantities in a column with units, and convert everything to SI before you substitute.
• State the formula you are using in symbols first, and then substitute numbers.
• Draw the diagram whenever the question involves rays, circuits or forces, even when the question does not ask for one. It helps the marker follow you and helps you avoid sign errors.
• Circle or underline the final answer, with the unit and direction where relevant.

Derivations and Diagrams to Know Cold

Derivations are worth learning as a short chain of ideas, not as paragraphs of text. The aim is to reproduce the key steps in the right order with correct diagrams. The list below is a general revision aid drawn from the standard NCERT flow. Board syllabi are trimmed from time to time, so cross-check each item against the current curriculum before you commit time to it.

• Electrostatics: field due to an infinitely long charged wire, a uniformly charged plane sheet and a thin spherical shell using Gauss's law; capacitance of a parallel plate capacitor, with and without a dielectric slab; energy stored in a capacitor.
• Current electricity: relation between drift velocity and current, and how it leads to Ohm's law and resistivity; balanced condition for a Wheatstone bridge.
• Magnetism and moving charges: magnetic field on the axis of a circular loop; field inside a long solenoid using Ampere's circuital law; force between two parallel current-carrying wires; torque on a current loop in a uniform field.
• Electromagnetic induction and AC: motional emf; self-inductance of a long solenoid; current and phase relations for AC through a resistor, inductor and capacitor; resonance in a series LCR circuit; working principle and turns-ratio relation of a transformer.
• Optics: Snell's law using Huygens' principle; mirror formula and lens-maker's formula; refraction at a spherical surface; the prism formula; fringe width in Young's double slit experiment; the single-slit diffraction pattern.
• Modern physics: Einstein's photoelectric equation; radius and energy of a Bohr orbit for hydrogen; binding energy and its variation with mass number.

Diagrams deserve their own list. Practise the ray diagrams for the astronomical telescope and compound microscope, refraction through a prism and the deviation curve, the circuit and waveform for a half-wave and a full-wave rectifier, an AC generator and a transformer, the energy-level diagram for hydrogen, and I-V characteristics of a p-n junction diode. Draw them with a pencil and a ruler, label every part, and check against NCERT. A neat, labelled diagram is usually where a two-mark answer becomes a full two marks.

The 30 Practical Marks

Physics carries 30 marks for practical work, and practical exams are conducted at the school level, usually before or around the time theory papers begin. The practical component typically includes an experiment component, a practical record file, an investigatory project or activity, and a viva voce. The exact split of marks between these can vary, so check the current CBSE practical syllabus and your school's schedule for the official breakdown. What is not in doubt is that it counts, that it is set at your school, and that the preparation is entirely within your control.

• Know the experiment list. The standard list in the CBSE practical syllabus includes exercises such as the meter bridge, a resistance-combination verification, converting a galvanometer into an ammeter or voltmeter, the u-v method for a convex lens, refractive index using a glass slab and a prism, and diode characteristics. Check the current list, because it is what your school will examine on.
• Practise the procedure aloud. For each experiment, be able to state the aim, the apparatus, the circuit or ray diagram, the observations you will tabulate, the formula and the main sources of error.
• Keep the file complete and neat. Every experiment in the list should have its diagram, observation table, calculation and result. A missing experiment is easy to notice.
• Prepare for the viva as a set of short questions. Expect why and how questions on the ones you did: why is a meter bridge used with a null point near the middle, what happens to the fringe width if the slit separation is doubled, why is a voltmeter connected in parallel.
• Know your project. Be ready to explain what you built, what you observed and what went wrong. Do not memorise a paragraph you cannot unpack.

A Simple Weekly Rhythm

A rhythm that works for most Class 12 students: two days on numerical sets from two chapters, one day for derivations and diagrams tested on a blank sheet, one day on practical file and viva, one day for a timed section or full paper, and a lighter day for the error log and formula sheet. In the final three weeks, swap the numerical days for board-pattern papers, and review each one against the marking scheme. Our note on why fast, detailed feedback beats a pile of practice papers explains why the review is where the improvement lives.

Competency-Based Questions in Physics

As per the pattern reported for 2026-27, about half the paper is competency-based; verify the current sample paper for the exact structure. In Physics, that means case-study passages, assertion-reason questions and applications of a concept to a situation the textbook does not print. Practise by taking a familiar idea and changing the setting: what happens to the induced emf if the loop is rotated instead of pulled, what changes in a lens problem if the object is placed in water. Students who can explain why each formula applies do better on these than students who can only apply it.

Common Mistakes to Avoid

• Writing only the final answer. You lose method marks even when you are right.
• Skipping units and direction. A field or force without a direction or unit is an incomplete answer.
• Mixing up sign conventions in optics. Decide on the Cartesian sign convention and stick to it in every problem.
• Memorising derivations without diagrams. Half of a derivation's marks often sit in a correct labelled figure.
• Ignoring the practical file until the last fortnight. It is preparation that pays back reliably, and it deserves a slot every week.
• Studying only from a problem book. NCERT text and its worked examples remain the base for what the board asks and how it words it.

Expert Tips from BuzzyBrains Academy Faculty

Founder Dilip Sah (IIT Kanpur alumnus, JEE AIR 400, 25+ years of mentoring experience), who leads Physics in our crash course, offers a few habits worth building:

• Solve every numerical twice. Once to get the answer, once as if you were writing it for an examiner who has never met you.
• Keep a one-page derivation map. For each derivation, write the starting law, the key step and the result in one line. Fill it in from memory each Sunday.
• Treat the viva as an exam. Students who prepare thirty short viva questions per experiment rarely lose marks there.

Physics is a subject where a small batch and quick feedback make a visible difference. Our 12th CBSE PCMB Crash Course drills Physics numericals and derivations in weeks 3-5, then runs board-pattern mocks in weeks 6-8. For the wider eight-week structure, see our 8-week crash plan for Physics, Chemistry, Maths and Biology. If you would like to ask whether the course suits your child, contact us; batch dates and seats are confirmed on the enrollment call.