This guide provides complete Class 12 Physics notes chapter-wise, including concepts, formulas, and explanations in simple language.

Class 12 Physics Notes: Chapter-wise Theory, Formulas, Examples & Questions

Chapter 1: Electric Charges and Fields

Theory

• Matter has two types of charges: positive and negative.

• Coulomb’s Law defines force between two charges.

• Electric Field (E): Space around a charge where its effect is felt.

• Electric Flux & Gauss’s Law help calculate electric field easily.

Formulas

1. Coulomb’s Law:

   F=14πϵ0⋅q1q2r2F = \frac{1}{4\pi \epsilon_0} \cdot \frac{q_1 q_2}{r^2}F=4πϵ0​1​⋅r2q1​q2​​

2. Electric Field due to Point Charge:

   E=14πϵ0⋅qr2E = \frac{1}{4\pi \epsilon_0} \cdot \frac{q}{r^2}E=4πϵ0​1​⋅r2q​

3. Electric Flux:

   $$\varphi =E\cdot A\cdot \cos \theta$$

4. Gauss’s Law:

   ∮E⋅dA=qϵ0\oint E \cdot dA = \frac{q}{\epsilon_0}∮E⋅dA=ϵ0​q​

Chapter 2: Electrostatic Potential and Capacitance

Theory

• Electrostatic Potential (V): Work done to bring unit positive charge from infinity to a point.

• Relation between Electric Field and Potential: $E=-dV/dr$.

• Capacitance (C): Ability to store charge.

Formulas

1. Potential due to Point Charge:

   V=14πϵ0⋅qrV = \frac{1}{4\pi \epsilon_0} \cdot \frac{q}{r}V=4πϵ0​1​⋅rq​

2. Capacitance of Parallel Plate Capacitor:

   C=ϵ0AdC = \frac{\epsilon_0 A}{d}C=dϵ0​A​

3. Energy Stored in Capacitor:

   U=12CV2U = \frac{1}{2}CV^2U=21​CV2

Chapter 3: Current Electricity

Theory

• Electric Current = Rate of flow of charge.

• Ohm’s Law: $V=IR$.

• Kirchhoff’s Laws used in circuit analysis.

• Resistivity depends on material.

Formulas

1. Resistance:

   R=ρlAR = \rho \frac{l}{A}R=ρAl​

2. Power:

   P=VI=I2R=V2RP = VI = I^2R = \frac{V^2}{R}P=VI=I2R=RV2​

3. Drift Velocity:

   vd=InAev_d = \frac{I}{nAe}vd​=nAeI​

Chapter 4: Moving Charges and Magnetism

Theory

• Moving charges produce magnetic fields.

• Right-hand rule gives direction of magnetic field.

• Biot-Savart Law & Ampere’s Law explain magnetic field due to currents.

Formulas

1. Magnetic Force on Charge:

   $$F=q(v\times B)$$

2. 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)​

3. Ampere’s Law:

   ∮B⋅dl=μ0I\oint B \cdot dl = \mu_0 I∮B⋅dl=μ0​I

Chapter 5: Magnetism and Matter

Theory

• Magnetic materials classified as Diamagnetic, Paramagnetic, Ferromagnetic.

• Earth behaves like a giant magnet.

• Magnetic dipole moment defines strength of a magnet.

Formulas

1. Magnetic Dipole Moment:

   $$M=m\cdot 2l$$

2. 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

• Faraday’s Law: Changing magnetic flux induces EMF.

• Lenz’s Law: Induced current opposes cause.

Formulas

1. Induced EMF:

   ϵ=−dϕdt\epsilon = -\frac{d\phi}{dt}ϵ=−dtdϕ​

2. Self-Inductance:

   ϵ=−LdIdt\epsilon = -L\frac{dI}{dt}ϵ=−LdtdI​

Chapter 7: Alternating Current (AC)

Theory

• AC changes direction and magnitude with time.

• Impedance, reactance, and resonance are key concepts.

Formulas

1. AC Voltage:

   V=V0sin⁡ωtV = V_0 \sin \omega tV=V0​sinωt

2. RMS Value:

   Vrms=V02V_{rms} = \frac{V_0}{\sqrt{2}}Vrms​=2​V0​​

3. Power in AC:

   P=VrmsIrmscos⁡ϕP = V_{rms} I_{rms} \cos \phiP=Vrms​Irms​cosϕ

Chapter 8: Electromagnetic Waves

Theory

• EM waves are produced by oscillating charges.

• Travel at speed of light in vacuum.

• Have electric and magnetic field components perpendicular to each other.

Formula

c=1μ0ϵ0c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}c=μ0​ϵ0​​1​

Chapter 9: Ray Optics and Optical Instruments

Theory

• Laws of reflection & refraction.

• Lens and mirror formula.

• Optical instruments like microscope, telescope.

Formulas

1. Mirror Formula:

   1f=1v+1u\frac{1}{f} = \frac{1}{v} + \frac{1}{u}f1​=v1​+u1​

2. 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)(R1​1​−R2​1​)

Chapter 10: Wave Optics

Theory

• Light shows interference, diffraction, polarization.

• Young’s Double Slit Experiment proves wave nature of light.

Formulas

1. Fringe Width:

   Δy=λDd\Delta y = \frac{\lambda D}{d}Δy=dλD​

Chapter 11: Dual Nature of Radiation and Matter

Theory

• Light behaves as particle (photon) & wave.

• Einstein explained photoelectric effect.

Formulas

1. Energy of Photon:

   E=hν=hcλE = h\nu = \frac{hc}{\lambda}E=hν=λhc​

2. Einstein’s Equation:

   hν=ϕ+Kmaxh\nu = \phi + K_{max}hν=ϕ+Kmax​

Chapter 12: Atoms

Theory

• Bohr’s model of atom explains stability of electrons.

• Energy levels are quantized.

Formulas

1. Radius of nth Orbit:

   rn=n2h24π2me2Zr_n = \frac{n^2 h^2}{4\pi^2 m e^2 Z}rn​=4π2me2Zn2h2​

2. Energy of nth Orbit:

   En=−13.6Z2n2 eVE_n = – \frac{13.6 Z^2}{n^2} \, eVEn​=−n213.6Z2​eV

Chapter 13: Nuclei

Theory

• Nucleus is made up of protons & neutrons.

• Nuclear binding energy explains stability.

Formulas

1. Mass Defect:

   Δm=Zmp+Nmn−M\Delta m = Zm_p + Nm_n – MΔm=Zmp​+Nmn​−M

2. Binding Energy:

   Eb=Δmc2E_b = \Delta m c^2Eb​=Δmc2

Chapter 14: Semiconductor Electronics

Theory

• Conductors, semiconductors, insulators differ by band gap.

• Diodes, transistors used in circuits.

Formulas

1. Resistivity of Semiconductor:

   ρ=1neμ\rho = \frac{1}{n e \mu}ρ=neμ1​

Chapter 15: Communication Systems

Theory

• Communication involves transmitter, medium, and receiver.

• Modulation (AM, FM, PM) used to transmit signals.

• 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.

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