Electrostatics (स्थिरवैद्युतिकी)
- Coulomb's Law: F = k q₁ q₂ / r² (k = 1/4πε₀ ≈ 9×10⁹ N m²/C²)
- Electric Field: E = F/q = kQ/r² (SI unit: N/C)
- Electric Potential: V = kQ/r (SI unit: volt)
- Capacitance: C = Q/V; parallel plate capacitor: C = ε₀ A / d
- Energy stored in capacitor: U = ½ CV² = Q²/2C
Current Electricity (धारा विद्युत)
- Ohm’s Law: V = IR
- Resistance: R = ρL/A (ρ = resistivity)
- Kirchhoff’s Laws: Junction rule (∑I = 0), Loop rule (∑V = 0)
- Power: P = VI = I²R = V²/R
- Cell in series/parallel: net EMF = E₁+E₂+..., net internal resistance = r₁+r₂+...
Magnetic Effects of Current & Magnetism
- Biot-Savart Law: dB = (μ₀/4π) Idl sinθ / r²
- Magnetic field due to straight wire: B = μ₀ I / (2πr)
- Force on moving charge: F = qvB sinθ (Lorentz force)
- Force on current-carrying wire: F = BIL sinθ
- Torque on coil: τ = NIAB sinθ
Electromagnetic Induction & AC
- Faraday’s Law: ε = -dΦ/dt (induced emf)
- Lenz’s Law: Direction opposes change in flux
- Inductance: L = NΦ/I ; energy in inductor: U = ½LI²
- AC Voltage: V = V₀ sin ωt ; I = I₀ sin(ωt + φ)
- Impedance: Z = √(R² + (X_L - X_C)²)
Optics (प्रकाशिकी)
- Mirror Formula: 1/f = 1/v + 1/u
- Magnification (mirror): m = -v/u
- Lens Formula: 1/f = 1/v - 1/u
- Magnification (lens): m = v/u
- Refractive Index: n = c/v ; Snell’s Law: n₁ sin i = n₂ sin r
- Young’s Double Slit: fringe width β = λD/d
Modern Physics (आधुनिक भौतिकी)
- Photoelectric Effect: K.E. max = hν - φ (φ = work function)
- de Broglie wavelength: λ = h/p = h/(mv)
- Bohr’s Model: radius r_n = n²a₀ (a₀ = 0.53 Å); energy E_n = -13.6/n² eV
- Nuclear Binding Energy: B = Δm c² (mass defect)
- Radioactive Decay: N = N₀ e^{-λt} ; half-life T₁/₂ = ln2/λ
Semiconductor Devices
- Diode current (Ideal): I = I₀ (e^{eV/kT} - 1)
- Zener diode: voltage regulator (reverse breakdown region)
- Transistor (npn/pnp): current gain β = I_C / I_B
- Logic Gates: AND (Y = A·B), OR (Y = A+B), NOT (Y = Ā)
Yeh formulas class 12 physics ke liye kaafi important hain. Inhe daily revise karo aur numerical problems practice karo. Samajhne ke baad khud se examples banao. Boards aur entrance exams (NEET, JEE) mein kaam aayenge.
