Class 12 Most important question for board exam 2025-2026

Electrostatics

1. State and explain Gauss’s theorem. Derive an expression for the electric field due to an infinitely long charged wire using Gauss’s law.
2. Derive the expression for the capacitance of a parallel plate capacitor with and without a dielectric medium.
3. Define electric flux and write its SI unit.
4. Two charges +q and −q are placed at a distance 2d2d2d apart. Find the electric field at the equatorial point.

Current Electricity

1. State and derive Ohm’s law using the concept of drift velocity.
2. Explain the color coding of resistors with an example.
3. Derive an expression for the equivalent resistance in a series and parallel combination of resistors.
4. What is Wheatstone’s bridge? Derive the condition for balance in the bridge.
5. Define electromotive force (EMF) and terminal voltage. Explain why the terminal voltage is always less than EMF.

magnetism & Moving Charges

1. State and explain Biot-Savart’s law. Derive an expression for the magnetic field at the center of a current-carrying circular loop.
2. Derive an expression for the force experienced by a charged particle moving in a uniform magnetic field.
3. Derive an expression for the magnetic field along the axis of a current-carrying solenoid.
4. State and explain Ampere’s Circuital Law.

Electromagnetic Induction & Alternating Current

1. State and explain Faraday’s laws of electromagnetic induction.
2. Derive an expression for self-inductance of a solenoid.
3. Derive an expression for the impedance in an LCR circuit.
4. What is power factor? How does it affect power consumption in an AC circuit ?

Electromagnetic Waves & Optics

1. Derive an expression for fringe width in Young’s double-slit experiment.
2. What is total internal reflection? Explain with the help of optical fibers.
3. What is resolving power? Derive an expression for the resolving power of a telescope.
4. Explain the principle of polarisation and mention its applications.
5. Derive prism formula.
6. State Huygens principle.
7. Lens makers formula.

Modern Physics

1. Derive the expression for the de Broglie wavelength of a particle.
2. What is the photoelectric effect? Explain Einstein’s photoelectric equation.
3. Draw and explain the I-V characteristics of a PN junction diode.
4. Explain the working of a transistor as an amplifier.

Nuclei & Semiconductor Devices

1. Explain nuclear fission and nuclear fusion with suitable examples.
2. What are logic gates? Draw the truth tables for AND, OR, NOT, NAND, and NOR gates.
3. What is rectification? Explain the working of a full-wave rectifier with a labelled diagram.