Guide
Class 12 physics investigatory project: how it is marked and how to present it
The CBSE practical marks, what "investigatory" means, 25 topics grouped by unit with matching kits, the file format examiners expect, and the viva questions to prepare for.
Overview
The investigatory project is a small part of the class 12 physics practical, but it is the part students worry about most, because it is the one they have to choose and explain themselves. Here is how it is assessed, how to pick a topic you can defend, and how to write it up.
How the practical is marked
In the CBSE class 12 physics scheme for 2025-26 the practical carries 30 marks: two experiments of 7 marks each, the practical record of 5 marks, one activity of 3 marks, the investigatory project of 3 marks, and the viva of 5 marks. So the project itself is worth 3 marks, but the viva, worth 5, often draws on it. A project you understand well earns marks twice. Check your school's copy of the current syllabus for the year you are appearing in.
What "investigatory" means
An investigatory project answers a question through an experiment. "Full wave rectifier" is a topic; "how does the ripple in a full wave rectifier change with the value of the filter capacitor?" is an investigation. The examiner looks for an aim, a method, observations you recorded yourself, and a conclusion that follows from them. A working model on its own is a demonstration, not an investigation, so add a measurement to it: a table of readings, a graph, a comparison.
Topics by unit, with the kit that fits
Electrostatics and current electricity
- Ohm's law and the effect of length and thickness on resistance (Ohm's law and pencil-resistor projects)
- Kirchhoff's laws verified on a two-loop circuit
- Wheatstone bridge: finding an unknown resistance
- Internal resistance of a cell from a potentiometer or voltmeter method
Electromagnetic induction and alternating current
- Step-up and step-down transformer: turns ratio against voltage ratio
- AC generator: output against speed of rotation
- Mutual induction between two coils with and without an iron core
- Series LCR circuit: resonance and the effect of frequency
Semiconductor electronics
- Half wave and full wave rectifier: output waveform and the effect of a filter capacitor
- Zener diode as a voltage regulator: line and load regulation
- Transistor as an amplifier: gain against load resistance
- Logic gates with diodes and transistors: truth tables for AND, OR, NOT, NAND and NOR
- LDR: variation of resistance with light intensity, and an automatic street light
Optics and modern physics
- Refractive index of liquids with a hollow prism
- Rutherford's experiment model and its interpretation
- Photoelectric effect demonstration (as a model with a report)
Most of these are in our class 10 to 12 physics range with a printed investigatory report; the rest are made to order.
The file format examiners expect
Schools differ in small ways, but the standard investigatory file has these pages in this order:
- Title page: topic, your name, class, roll number, school, session.
- Certificate signed by the teacher, and an acknowledgement.
- Index.
- Aim, in one sentence.
- Theory: the principle in your own words, with the circuit diagram.
- Apparatus and materials, with values (for example, 1 kilo-ohm resistor, 1000 microfarad capacitor).
- Procedure, as numbered steps.
- Observations: the table of readings and any graph.
- Result and conclusion: what the readings show, and whether it matches the theory.
- Precautions and sources of error.
- Bibliography.
Write the observations from readings you took yourself. A printed report from a kit gives you the theory, the diagram and a sample table; the examiner wants your numbers in the table.
Viva questions to prepare
- Why did you choose this topic, and which chapter is it from?
- Explain the circuit diagram from the input to the output.
- Why this component value? What happens if you double it?
- What did you measure, and what did you expect?
- What are the sources of error, and how did you reduce them?
- Where is this principle used in everyday devices?
Rehearse the answers with the model in front of you. Examiners ask you to point to the part you are describing.
Timeline
Projects are usually allotted early in the session and the practical is held in January or February. Aim to have the model working by November, the readings taken by December, and the file written before the winter break, so that January is only revision.
Getting a kit
Every kit in the class 10 to 12 range opens on Amazon or Flipkart from its card. For a topic that is not listed, or for a different circuit value, message us on WhatsApp with the topic and the date you need it by.
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