Physics Formulas Sheet
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✧
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PHYSICS
FORMULA SHEET
✦ CLASS 12 ✦
1. Electrostatics
• Coulomb's Law
F = 1/4πε₀
· q₁q₂/r²
• Electric Field
E = 1/4πε₀
· Q/r²
• Electric Potential
V = 1/4πε₀
· Q/r
• Capacitance
C = Q/V
• Energy Stored in Capacitor
U = ½CV²
2. Current Electricity
• Ohm's Law
V = IR
• Power
P = VI = I²R = V²/R
• Resistance
R = ρ L/A
• Series Combination
Rs = R₁ + R₂ + R₃ + ...
• Parallel Combination
1/Rp
=
1/R₁
+
1/R₂
+
1/R₃
• Kirchhoff's Laws
ΣI = 0 ΣV = 0
3. Magnetic Effects of Current
• Magnetic Field (long wire)
B = μ₀I/2πr
• Magnetic Field (coil)
B = μ₀NI/2R
• Force on Moving Charge
F = qvB sin θ
• Force on Current Carrying Conductor
F = BIL sin θ
• Torque on Coil
τ = NIBA sin θ
4. Electromagnetic Induction
• Magnetic Flux
Φ = BA cos θ
• Faraday's Law
E = − dΦ/dt
• Lenz's Law
Induced emf opposes the change in flux.
• Inductance L = NΦ/I • Energy Stored in Inductor U = ½LI²5. Alternating Current
• Instantaneous Values
v = V₀ sin ωt
i = I₀ sin ωt
• RMS Values
Vrms =
V₀/√2
Irms =
I₀/√2
• Reactance
XL = ωL
XC = 1/ωC
• Impedance
Z = √[R² + (XL − XC)²]
• Power
P = VrmsIrms cos φ
6. Ray Optics
• Mirror Formula
1/f
=
1/v
+
1/u
• Lens Formula
1/f
=
1/v
−
1/u
• Magnification
m = hᵢ/h₀
= v/u
• Power of Lens
P = 1/f
(in dioptre)
7. Wave Optics
• Path Difference
Δ = d sin θ
• Constructive Interference
Δ = nλ
• Destructive Interference
Δ = (n + ½)λ
• Young's Double Slit
β = λD/d
• Resolving Power (Grating)
R = nN
8. Dual Nature of Radiation & Matter
• Photoelectric Equation
hν = φ + Kmax
• Einstein's Equation
Kmax = hν − φ
• de Broglie Wavelength
λ = h/p
= h/mv
• Uncertainty Principle
Δx Δp ≥ h/4π
9. Atoms & Nuclei
• Bohr's Model
mvr = nh/2π
• Energy Levels
En =
− 13.6/n² eV
• Radioactive Decay
N = N₀e−λt
• Half Life
T1/2 =
0.693/λ
• Mass-Energy Relation
E = mc²
10. Semiconductor Electronics
• PN Junction Diode
P | N
• Forward Bias
Diode conducts current in forward direction.
• Reverse BiasVery small reverse current flows.
• Zener DiodeUsed for voltage regulation.
• Logic Gates AND OR NOT NAND NOR11. Communication Systems
• Amplitude Modulation (AM)
s(t) = [Ac + m(t)]
cos ωct
• Frequency Modulation (FM)
s(t) =
Ac cos
[ωct +
kf∫m(t)dt]
• Block Diagram
Transmitter
→
Channel
→
Receiver
IMPORTANT CONSTANTS
• Speed of light (c) = 3.00 × 10⁸ m/s
• Permittivity (ε₀) = 8.85 × 10⁻¹² C²/N·m²
• Permeability (μ₀) = 4π × 10⁻⁷ H/m
• Electron charge (e) = 1.6 × 10⁻¹⁹ C
• Planck's constant (h) = 6.626 × 10⁻³⁴ J·s
• Boltzmann constant (k) = 1.38 × 10⁻²³ J/K
• Gas constant (R) = 8.314 J/mol·K
• Gravitational constant (G) = 6.674 × 10⁻¹¹ N·m²/kg²
• Acceleration due to gravity (g) = 9.8 m/s²
✓ STUDY TIPS
☑ Understand the concept first.
☑ Memorize formulas with meaning.
☑ Solve numerical problems daily.
☑ Revise regularly.
☑ Practice previous year questions.
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