Class 12 Physics – All Important Formulae
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Magnetic Effect of Current
Biot–Savart Law
dB = (μ₀/4π)(Idl sinθ / r²)
Field (Long Wire)
B = μ₀I / 2πr
Force on Charge
F = qvB sinθ
Force on Wire
F = BIL sinθ
Ampere’s Law
∮B·dl = μ₀I
Electromagnetic Induction (EMI)
Magnetic Flux
Φ = BA cosθ
Faraday’s Law
ε = −dΦ/dt
Self Inductance
ε = −L(dI/dt)
Energy in Inductor
U = ½LI²
Alternating Current
AC Voltage
V = V₀ sinωt
RMS Voltage
Vrms = V₀/√2
Impedance
Z = √(R²+(XL−XC)²)
Power
P = VrmsIrmscosφ
Ray & Wave Optics
Mirror Formula
1/f = 1/v + 1/u
Lens Formula
1/f = 1/v + 1/u
Magnification
m = v/u
Young’s Fringe Width
β = λD/d
Diffraction
a sinθ = nλ
Dual Nature of Radiation
Einstein Equation
hν = φ + KE
Stopping Potential
eV₀ = KEmax
Photon Energy
E = hν
Electromagnetic Waves
Speed of EM Wave
c = 1/√(μ₀ε₀)
Relation
E/B = c
Semiconductor Electronics
Diode Equation
I = I₀(eV/ηVT − 1)
Logic Gates
AND, OR, NOT
Magnetic Materials
Magnetization
M = χH
Susceptibility
χ = M/H
Relative Permeability
μr = 1 + χ