Physics is one of the core subjects in Class 12 and forms the foundation for higher studies in engineering, medical, and science streams. The subject deals with matter, energy, force, motion, and their interactions. Understanding both the theory and formulas is crucial for scoring well in board exams and competitive exams like JEE & NEET.
This guide provides complete Class 12 Physics notes chapter-wise, including concepts, formulas, and explanations in simple language.
Table of Contents
ToggleClass 12 Physics Notes: Chapter-wise Theory, Formulas, Examples & Questions
Chapter 1: Electric Charges and Fields
Theory
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Matter has two types of charges: positive and negative.
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Coulomb’s Law defines force between two charges.
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Electric Field (E): Space around a charge where its effect is felt.
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Electric Flux & Gauss’s Law help calculate electric field easily.
Formulas
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Coulomb’s Law:
F=14πϵ0⋅q1q2r2F = \frac{1}{4\pi \epsilon_0} \cdot \frac{q_1 q_2}{r^2}F=4πϵ01⋅r2q1q2
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Electric Field due to Point Charge:
E=14πϵ0⋅qr2E = \frac{1}{4\pi \epsilon_0} \cdot \frac{q}{r^2}E=4πϵ01⋅r2q
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Electric Flux:
ϕ=E⋅A⋅cosθ\phi = E \cdot A \cdot \cos \thetaϕ=E⋅A⋅cosθ
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Gauss’s Law:
∮E⋅dA=qϵ0\oint E \cdot dA = \frac{q}{\epsilon_0}∮E⋅dA=ϵ0q
Chapter 2: Electrostatic Potential and Capacitance
Theory
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Electrostatic Potential (V): Work done to bring unit positive charge from infinity to a point.
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Relation between Electric Field and Potential: E=−dV/drE = -dV/drE=−dV/dr.
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Capacitance (C): Ability to store charge.
Formulas
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Potential due to Point Charge:
V=14πϵ0⋅qrV = \frac{1}{4\pi \epsilon_0} \cdot \frac{q}{r}V=4πϵ01⋅rq
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Capacitance of Parallel Plate Capacitor:
C=ϵ0AdC = \frac{\epsilon_0 A}{d}C=dϵ0A
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Energy Stored in Capacitor:
U=12CV2U = \frac{1}{2}CV^2U=21CV2
Chapter 3: Current Electricity
Theory
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Electric Current = Rate of flow of charge.
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Ohm’s Law: V=IRV = IRV=IR.
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Kirchhoff’s Laws used in circuit analysis.
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Resistivity depends on material.
Formulas
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Resistance:
R=ρlAR = \rho \frac{l}{A}R=ρAl
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Power:
P=VI=I2R=V2RP = VI = I^2R = \frac{V^2}{R}P=VI=I2R=RV2
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Drift Velocity:
vd=InAev_d = \frac{I}{nAe}vd=nAeI
Chapter 4: Moving Charges and Magnetism
Theory
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Moving charges produce magnetic fields.
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Right-hand rule gives direction of magnetic field.
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Biot-Savart Law & Ampere’s Law explain magnetic field due to currents.
Formulas
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Magnetic Force on Charge:
F=q(v×B)F = q(v \times B)F=q(v×B)
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Biot-Savart Law:
dB=μ04π⋅I(dl×r)r3dB = \frac{\mu_0}{4\pi} \cdot \frac{I(dl \times r)}{r^3}dB=4πμ0⋅r3I(dl×r)
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Ampere’s Law:
∮B⋅dl=μ0I\oint B \cdot dl = \mu_0 I∮B⋅dl=μ0I
Chapter 5: Magnetism and Matter
Theory
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Magnetic materials classified as Diamagnetic, Paramagnetic, Ferromagnetic.
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Earth behaves like a giant magnet.
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Magnetic dipole moment defines strength of a magnet.
Formulas
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Magnetic Dipole Moment:
M=m⋅2lM = m \cdot 2lM=m⋅2l
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Magnetic Field due to a Dipole (Axial Line):
B=μ04π⋅2Mr3B = \frac{\mu_0}{4\pi} \cdot \frac{2M}{r^3}B=4πμ0⋅r32M
Chapter 6: Electromagnetic Induction
Theory
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Faraday’s Law: Changing magnetic flux induces EMF.
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Lenz’s Law: Induced current opposes cause.
Formulas
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Induced EMF:
ϵ=−dϕdt\epsilon = -\frac{d\phi}{dt}ϵ=−dtdϕ
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Self-Inductance:
ϵ=−LdIdt\epsilon = -L\frac{dI}{dt}ϵ=−LdtdI
Chapter 7: Alternating Current (AC)
Theory
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AC changes direction and magnitude with time.
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Impedance, reactance, and resonance are key concepts.
Formulas
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AC Voltage:
V=V0sinωtV = V_0 \sin \omega tV=V0sinωt
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RMS Value:
Vrms=V02V_{rms} = \frac{V_0}{\sqrt{2}}Vrms=2V0
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Power in AC:
P=VrmsIrmscosϕP = V_{rms} I_{rms} \cos \phiP=VrmsIrmscosϕ
Chapter 8: Electromagnetic Waves
Theory
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EM waves are produced by oscillating charges.
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Travel at speed of light in vacuum.
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Have electric and magnetic field components perpendicular to each other.
Formula
c=1μ0ϵ0c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}c=μ0ϵ01
Chapter 9: Ray Optics and Optical Instruments
Theory
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Laws of reflection & refraction.
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Lens and mirror formula.
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Optical instruments like microscope, telescope.
Formulas
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Mirror Formula:
1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1=v1+u1
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Lens Maker’s Formula:
1f=(n−1)(1R1−1R2)\frac{1}{f} = (n-1)\left(\frac{1}{R_1} – \frac{1}{R_2}\right)f1=(n−1)(R11−R21)
Chapter 10: Wave Optics
Theory
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Light shows interference, diffraction, polarization.
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Young’s Double Slit Experiment proves wave nature of light.
Formulas
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Fringe Width:
Δy=λDd\Delta y = \frac{\lambda D}{d}Δy=dλD
Chapter 11: Dual Nature of Radiation and Matter
Theory
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Light behaves as particle (photon) & wave.
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Einstein explained photoelectric effect.
Formulas
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Energy of Photon:
E=hν=hcλE = h\nu = \frac{hc}{\lambda}E=hν=λhc
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Einstein’s Equation:
hν=ϕ+Kmaxh\nu = \phi + K_{max}hν=ϕ+Kmax
Chapter 12: Atoms
Theory
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Bohr’s model of atom explains stability of electrons.
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Energy levels are quantized.
Formulas
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Radius of nth Orbit:
rn=n2h24π2me2Zr_n = \frac{n^2 h^2}{4\pi^2 m e^2 Z}rn=4π2me2Zn2h2
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Energy of nth Orbit:
En=−13.6Z2n2 eVE_n = – \frac{13.6 Z^2}{n^2} \, eVEn=−n213.6Z2eV
Chapter 13: Nuclei
Theory
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Nucleus is made up of protons & neutrons.
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Nuclear binding energy explains stability.
Formulas
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Mass Defect:
Δm=Zmp+Nmn−M\Delta m = Zm_p + Nm_n – MΔm=Zmp+Nmn−M
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Binding Energy:
Eb=Δmc2E_b = \Delta m c^2Eb=Δmc2
Chapter 14: Semiconductor Electronics
Theory
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Conductors, semiconductors, insulators differ by band gap.
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Diodes, transistors used in circuits.
Formulas
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Resistivity of Semiconductor:
ρ=1neμ\rho = \frac{1}{n e \mu}ρ=neμ1
Chapter 15: Communication Systems
Theory
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Communication involves transmitter, medium, and receiver.
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Modulation (AM, FM, PM) used to transmit signals.
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Bandwidth decides data carrying capacity.
Conclusion
Class 12 Physics covers a wide range of concepts from electrostatics to modern physics. By understanding the theory and memorizing key formulas, students can easily solve problems in both board exams and competitive exams. These notes provide a complete one-stop reference for revision.