CBSE Class 12 Physics Notes 2025 – All Chapters, Formulas, and Important Topics

Physics is one of the most important subjects in the CBSE Class 12 Science stream. It forms the foundation for careers in engineering, research, and technology. However, due to its conceptual depth and vast syllabus, many students find it challenging to revise during exams.

That’s why we’ve created these detailed CBSE Class 12 Physics Notes — covering every chapter, topic, definition, derivation, and formula in a simplified way. These notes are designed to help you revise the complete syllabus quickly and effectively before exams.

CBSE Class 12 Physics Notes 2025 – All Chapters, Formulas, and Important Topics

Chapter 1: Electric Charges and Fields

Key Concepts

• Electric charge: Positive or negative property of matter.

• Like charges repel, unlike charges attract.

• Coulomb’s Law:
  F=14πϵ0⋅q1q2r2F = \dfrac{1}{4\pi \epsilon_0} \cdot \dfrac{q_1 q_2}{r^2}F=4πϵ0​1​⋅r2q1​q2​​

• Unit of charge: Coulomb (C)

• Electric field: Force per unit charge.
  E=FqE = \dfrac{F}{q}E=qF​

• Electric field due to a point charge:
  E=14πϵ0⋅qr2E = \dfrac{1}{4\pi \epsilon_0} \cdot \dfrac{q}{r^2}E=4πϵ0​1​⋅r2q​

• Electric dipole: Two equal and opposite charges separated by distance $2a$

• Electric dipole moment: $p=q\times 2a$

• Electric flux: $\varphi =E\cdot A\cos \theta$

• Gauss’s Law:
  ∮E⋅dA=qenclosedϵ0\oint E \cdot dA = \dfrac{q_{\text{enclosed}}}{\epsilon_0}∮E⋅dA=ϵ0​qenclosed​​

Chapter 2: Electrostatic Potential and Capacitance

Key Points

• Electrostatic potential (V): Work done in bringing a unit charge from infinity to a point.
  V=14πϵ0⋅qrV = \dfrac{1}{4\pi \epsilon_0} \cdot \dfrac{q}{r}V=4πϵ0​1​⋅rq​

• Potential difference: $V=W/q$

• Relation between E and V: E=−dVdrE = -\dfrac{dV}{dr}E=−drdV​

• Capacitance: C=qVC = \dfrac{q}{V}C=Vq​

• Capacitance of parallel plate capacitor:
  C=ϵ0AdC = \dfrac{\epsilon_0 A}{d}C=dϵ0​A​

• Energy stored in capacitor:
  U=12CV2U = \dfrac{1}{2}CV^2U=21​CV2

• Dielectric effect: Increases capacitance by factor $K$:
  C′=KCC’ = KCC′=KC

Chapter 3: Current Electricity

Important Concepts

• Electric current: I=dqdtI = \dfrac{dq}{dt}I=dtdq​

• Ohm’s Law: $V=IR$

• Resistance: R=ρlAR = \rho \dfrac{l}{A}R=ρAl​

• Resistivity depends on material and temperature.

• Series combination: Rs=R1+R2+R3R_s = R_1 + R_2 + R_3Rs​=R1​+R2​+R3​

• Parallel combination: 1Rp=1R1+1R2+1R3\dfrac{1}{R_p} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3}Rp​1​=R1​1​+R2​1​+R3​1​

• Kirchhoff’s Laws:

  • Current Law: Sum of currents entering a junction = sum leaving it.

  • Voltage Law: Sum of potential differences in a closed loop = 0.

• EMF: Energy per unit charge provided by source.

• Power: P=VI=I2R=V2RP = VI = I^2R = \dfrac{V^2}{R}P=VI=I2R=RV2​

Chapter 4: Moving Charges and Magnetism

Formulas & Notes

• Magnetic field due to current in straight wire:
  B=μ0I2πrB = \dfrac{\mu_0 I}{2\pi r}B=2πrμ0​I​

• Biot–Savart Law:
  dB=μ04π⋅Idlsin⁡θr2dB = \dfrac{\mu_0}{4\pi} \cdot \dfrac{Idl \sin\theta}{r^2}dB=4πμ0​​⋅r2Idlsinθ​

• Force on moving charge:
  F=q(v⃗×B⃗)F = q(\vec{v} \times \vec{B})F=q(v×B)

• Force on current-carrying conductor:
  $F=BIL\sin \theta$

• Torque on current loop: $\tau =BIA\sin \theta$

• Ampere’s Law: ∮B⋅dl=μ0I\oint B \cdot dl = \mu_0 I∮B⋅dl=μ0​I

Chapter 5: Magnetism and Matter

Important Notes

• Magnetic moment (M): $M=m\times 2l$

• Earth’s magnetic field:
  Components – Horizontal (BHB_HBH​), Vertical (BVB_VBV​)

• Magnetic declination: Angle between magnetic and geographic meridian.

• Magnetic dip: Angle between magnetic field and horizontal.

• Magnetic intensity: H=BμH = \dfrac{B}{\mu}H=μB​

• Magnetic materials: Diamagnetic, Paramagnetic, Ferromagnetic.

Chapter 6: Electromagnetic Induction

Formulas

• Faraday’s Law:
  ϵ=−dϕdt\epsilon = -\dfrac{d\phi}{dt}ϵ=−dtdϕ​

• Lenz’s Law: Direction opposes the cause.

• Induced EMF in coil: ϵ=−Ndϕdt\epsilon = -N \dfrac{d\phi}{dt}ϵ=−Ndtdϕ​

• Self-inductance: L=NϕIL = \dfrac{N\phi}{I}L=INϕ​

• Energy stored in inductor: U=12LI2U = \dfrac{1}{2}LI^2U=21​LI2

• Mutual Inductance: M=N2ϕ2I1M = \dfrac{N_2 \phi_2}{I_1}M=I1​N2​ϕ2​​

Chapter 7: Alternating Current (AC)

Key Concepts

• AC voltage: V=V0sin⁡ωtV = V_0 \sin \omega tV=V0​sinωt

• RMS value: Vrms=V02V_{\text{rms}} = \dfrac{V_0}{\sqrt{2}}Vrms​=2​V0​​

• Mean value: Vavg=2V0πV_{\text{avg}} = \dfrac{2V_0}{\pi}Vavg​=π2V0​​

• Impedance: Z=R2+(XL−XC)2Z = \sqrt{R^2 + (X_L – X_C)^2}Z=R2+(XL​−XC​)2​

• Resonance: XL=XCX_L = X_CXL​=XC​

• Power factor: cos⁡ϕ=RZ\cos\phi = \dfrac{R}{Z}cosϕ=ZR​

• Power in AC: P=VrmsIrmscos⁡ϕP = V_{\text{rms}} I_{\text{rms}} \cos\phiP=Vrms​Irms​cosϕ

Chapter 8: Electromagnetic Waves

Summary

• EM waves: Combination of oscillating E and B fields.

• Speed in vacuum: c=1μ0ϵ0c = \dfrac{1}{\sqrt{\mu_0 \epsilon_0}}c=μ0​ϵ0​​1​

• EM Spectrum:
  Radio → Microwave → Infrared → Visible → UV → X-rays → Gamma rays.

• Applications:

  • Radio waves – communication

  • X-rays – medical imaging

  • Infrared – remote controls

Chapter 9: Ray Optics and Optical Instruments

Key Notes

• Reflection law: Angle of incidence = angle of reflection.

• Refraction law (Snell’s Law):
  n1sin⁡i=n2sin⁡rn_1 \sin i = n_2 \sin rn1​sini=n2​sinr

• Mirror formula:
  1f=1v+1u\dfrac{1}{f} = \dfrac{1}{v} + \dfrac{1}{u}f1​=v1​+u1​

• Magnification: m=h2h1=vum = \dfrac{h_2}{h_1} = \dfrac{v}{u}m=h1​h2​​=uv​

• Lens formula:
  1f=1v−1u\dfrac{1}{f} = \dfrac{1}{v} – \dfrac{1}{u}f1​=v1​−u1​

• Power of lens: P=1fP = \dfrac{1}{f}P=f1​ (in meters)

• Optical instruments:

  • Microscope

  • Telescope

Chapter 10: Wave Optics

Concepts

• Interference: Superposition of two coherent waves.

• Path difference for constructive interference: $n\lambda$

• Young’s double slit:
  Fringe width β=λDd\beta = \dfrac{\lambda D}{d}β=dλD​

• Diffraction: Bending of light around obstacles.

• Polarisation: Restricting vibration of light in one plane.

Chapter 11: Dual Nature of Radiation and Matter

Important Points

• Photoelectric effect: Emission of electrons by light.

• Einstein’s photoelectric equation:
  Ek=hν−ϕE_k = h\nu – \phiEk​=hν−ϕ

• Work function: Minimum energy required to eject electron.

• de Broglie wavelength:
  λ=hp=hmv\lambda = \dfrac{h}{p} = \dfrac{h}{mv}λ=ph​=mvh​

Chapter 12: Atoms

Summary

• Rutherford Model: Nucleus at center, electrons revolve around it.

• Bohr’s Model:
  En=−13.6n2E_n = -\dfrac{13.6}{n^2}En​=−n213.6​ eV
  rn=n2a0r_n = n^2 a_0rn​=n2a0​

• Spectrum of hydrogen:
  1λ=RH(1n12−1n22)\dfrac{1}{\lambda} = R_H \left( \dfrac{1}{n_1^2} – \dfrac{1}{n_2^2} \right)λ1​=RH​(n12​1​−n22​1​)

Chapter 13: Nuclei

Concepts

• Atomic mass unit: 1 u = 931.5 MeV

• Mass defect: Δm=Zmp+(A−Z)mn−M\Delta m = Zm_p + (A-Z)m_n – MΔm=Zmp​+(A−Z)mn​−M

• Binding energy: EB=Δmc2E_B = \Delta m c^2EB​=Δmc2

• Nuclear fission: Splitting of nucleus (U-235)

• Nuclear fusion: Combining light nuclei (Sun energy)

Chapter 14: Semiconductor Electronics

Key Notes

• Types: Intrinsic and Extrinsic semiconductors

• Doping increases conductivity.

• p-type: Holes are majority carriers.
  n-type: Electrons are majority carriers.

• PN junction diode: Allows current in one direction.

• Forward bias and reverse bias characteristics.

• Logic gates:
  AND, OR, NOT, NAND, NOR, XOR.

Chapter 15: Communication Systems

Important Concepts

• Elements of communication: Transmitter, Channel, Receiver.

• Modulation: Mixing message signal with carrier.

• Types of modulation: AM, FM, PM.

• Bandwidth: Range of frequencies.

• Propagation:

  • Ground wave

  • Sky wave

  • Space wave

Conclusion

Class 12 Physics is not just about memorizing formulas — it’s about understanding how the universe works. These chapter-wise notes cover all key topics, derivations, and formulas that are vital for your CBSE board exams and entrance tests like JEE or NEET.

Revise these formulas regularly, practice previous year questions, and focus on concept clarity to score above 90% in your CBSE Class 12 Physics exam.

Top 10 FAQs on CBSE Class 12 Physics Notes

1. Are NCERT books enough for Class 12 Physics board exams?

Yes, NCERT is the base for CBSE exams. All questions are conceptually based on it.

2. How can I memorize physics formulas easily?

Write them down chapter-wise and revise daily using flashcards.

3. Which chapters are most important for CBSE Physics?

Ray Optics, Current Electricity, Electrostatics, and Dual Nature are high-weightage chapters.

4. How to prepare for derivations in Physics?

Understand the logic behind each step rather than rote learning.

5. What is the best way to revise Class 12 Physics before exams?

Use short notes, practice numerical questions, and solve past papers.

6. Are numericals asked in CBSE Physics exam?

Yes, at least 2–3 numerical questions are expected in long-answer sections.

7. Can I skip difficult chapters?

It’s not advisable; even smaller chapters carry marks. Cover at least basics of each.

8. How many hours should I study Physics daily?

2 hours of focused study with practice is enough for consistent improvement.

9. Is Physics tougher than Chemistry in Class 12?

It depends on your understanding. With practice, Physics becomes easier.

10. Do practical experiments matter for board marks?

Yes, practicals carry 30 marks — do not neglect them.

CBSE Class 12 Physics Notes 2025

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