CBSE Physics Class 12:
Formulas, Flashcards & AI Tools
Complete formula reference organised by board weightage, plus AI tools that generate chapter summaries and flashcards from your NCERT Physics notes.
Generate Physics flashcards free → 📄 Download free PDFWhere the marks actually are
| Chapter / Unit | Typical marks | Priority |
|---|---|---|
| Electrostatics & Capacitance | 8–9 marks | High |
| Current Electricity | 7–8 marks | High |
| Magnetism & Moving Charges | 8 marks | High |
| EMI & AC Circuits | 8 marks | High |
| Ray Optics & Wave Optics | 10 marks | High |
| Modern Physics (Atoms, Nuclei, Semiconductors) | 10 marks | High |
| Dual Nature (Photoelectric effect) | 4–5 marks | Medium |
| Communication Systems | 2–3 marks | Lower |
Weightage varies by year. Electrostatics, Optics, and Modern Physics are consistently the highest-yield chapters for boards.
High-weightage formulas by chapter
Electrostatics & Capacitance
- F = kq₁q₂/r² (k = 9×10⁹)
- E = kq/r² | V = kq/r
- C = Q/V | C₀ = ε₀A/d
- With dielectric: C = kε₀A/d
- Energy: U = ½CV² = Q²/2C
- Gauss: Φ = q_enc/ε₀
Current Electricity
- V = IR | R = ρL/A
- Drift: I = nAev_d
- Power: P = VI = I²R = V²/R
- Series: R_eq = ΣR
- Parallel: 1/R_eq = Σ(1/R)
- KCL: ΣI = 0 | KVL: ΣV = 0
Magnetism & EMI / AC
- F = qvB sinθ | F = BIL sinθ
- Solenoid: B = μ₀nI
- Faraday: ε = −NdΦ/dt
- X_L = ωL | X_C = 1/ωC
- Z = √(R² + (X_L−X_C)²)
- Resonance: f_r = 1/2π√LC
Optics
- Mirror: 1/v + 1/u = 1/f
- Lens: 1/v − 1/u = 1/f
- Snell: n₁sinθ₁ = n₂sinθ₂
- Young's: β = λD/d
- Power P = 1/f (dioptres)
- Critical: sinC = n₂/n₁
Modern Physics
- E = hν = hc/λ (h = 6.63×10⁻³⁴)
- KE_max = hν − φ
- de Broglie: λ = h/p
- Bohr: E_n = −13.6/n² eV
- r_n = 0.529n² Å
- E = mc² | N = N₀e^(−λt)
Most-Forgotten Facts
- dim(ε₀) = C²N⁻¹m⁻² = F/m
- At resonance: Z = R (minimum)
- Concave mirror: f < 0
- RMS = peak / √2
- TIR requires n₁ > n₂ and θ > θ_c
- EFL: sign conventions from pole
Turn your Physics notes into flashcards in 30 seconds
Paste any NCERT Physics chapter. Get exam-style Q&As covering the exact concepts boards ask — from Gauss's Law to the Bohr model.
Generate flashcards free →How to maximise marks in Physics
For derivations (5-mark questions)
Always write: Given → Diagram (where applicable) → Formula statement → Derivation steps → Final result boxed. Boards give method marks at each step — a wrong final answer can still score 3–4 marks.
Sign convention errors (most common loss)
All distances in the New Cartesian convention are measured from the pole (mirrors) or optical centre (lenses). Incident light travels left to right by convention. Distances in the direction of light are positive.
Formula memory trick for AC circuits
Draw a right triangle: R on the base, (X_L − X_C) on the height, Z as hypotenuse. Resonance = when the height = 0, leaving Z = R. Power factor cosφ = R/Z.
Modern Physics pattern
Boards ask Bohr model, photoelectric effect, and de Broglie almost every year. These three together are ~8 marks. Know: E = hν and KE_max = hν − φ and λ = h/p cold.