Class 12 Physics Chapter 1 Electric Charges and Fields is the first chapter of electrostatics. It introduces Coulomb's law, the electric field, the electric dipole, and Gauss's law. It carries 6 marks in CBSE and 4 to 5 percent in JEE Main.
Here is what this chapter is worth across the main exams:
- CBSE Boards: 6 marks, usually one 5-mark Gauss's-law derivation plus one 1-mark on Coulomb's law.
- JEE Main: 4 to 5 percent, two questions per shift on Coulomb's law, dipole, and Gauss applications.
- NEET: 1 to 2 questions every year on point-charge field and dipole concepts.
Student Feedback: We asked 13,150 Class 12 students. 71% found the dipole equatorial-field derivation the hardest part.
Class 12 Physics Chapter 1 Notes: Topic-by-Topic Summary
The chapter splits into five blocks, each with its CBSE marking pattern.
- Charge and properties: quantisation q = ne, conservation, additivity. 1 mark.
- Coulomb's law: vector form and superposition of charges. 3 marks.
- Field and dipole: field lines, axial and equatorial dipole field. 3 to 5 marks.
- Flux and Gauss's law: wire, sheet and shell applications. 5 marks.
- Charge distributions: linear λ, surface σ and volume ρ densities. 3 marks.
Electric Charges and Fields All Formulas
Every numerical comes from these formulas, also printed on the PDF cover sheet.
| Concept | Formula | SI Unit |
|---|---|---|
| Coulomb's law | F = k q₁q₂ / r² | newton |
| Coulomb's constant | k = 1 / 4πε₀ = 9 × 10⁹ N m² / C² | n/a |
| Charge quantisation | q = ne; e = 1.602 × 10⁻¹⁹ C | coulomb |
| Electric field (point charge) | E = k Q / r² | N/C |
| Dipole moment | p = q × 2a | C m |
| Dipole field (axial) | E = 2kp / r³ | N/C |
| Dipole field (equatorial) | E = kp / r³ | N/C |
| Torque on dipole | τ = p × E; |τ| = pE sin θ | N m |
| Electric flux | Φ = ∮ E·dA | V m |
| Gauss's law | ∮ E·dA = qenc / ε₀ | n/a |
| Field of infinite wire | E = λ / 2πε₀r | N/C |
| Field of plane sheet | E = σ / 2ε₀ | N/C |
Full formula sheet with derivations: Class 12 Physics Chapter 1 Formula Sheet
Key Definitions and Derivations
Seven derivations carry most of the marks. Each needs its geometry sketch, integral set-up and boundary condition.
- Coulomb's law in vector form with superposition. 3 marks.
- Dipole field on the axial line. 3 marks.
- Dipole field on the equatorial line. 3 marks.
- Torque on a dipole in a uniform field. 2 marks.
- Gauss's law: infinite line of charge. 5 marks.
- Gauss's law: infinite plane sheet. 5 marks.
- Gauss's law: charged spherical shell. 5 marks.
Electric Charges and Fields Class 12 Video Lecture
Source: Magnet Brains on YouTube
Common Mistakes in Electric Charges and Fields
- Treating Coulomb's law as scalar. Add forces as vector components; this is the top reason the superposition answer goes wrong.
- Swapping the axial and equatorial dipole field. Axial is 2kp/r³, equatorial is kp/r³. Box the factor of 2.
- Choosing the wrong Gaussian surface. Cylinder for a wire or sheet, sphere for a shell. The wrong surface loses all 5 marks.
- Confusing E inside a conductor (= 0) with E inside a solid non-conducting sphere (not zero; depends on r).
Each slip costs 1 to 2 marks.
Electric Charges and Fields Weightage in CBSE, JEE and NEET
Chapter 1 has stayed at a steady 6 marks in CBSE over recent years.
| Year | CBSE Board | JEE Main | NEET |
|---|---|---|---|
| 2025 | Coulomb force on three charges (5) | Flux through a closed surface (4) | Field due to a dipole (4) |
| 2024 | Field of an infinite sheet (3) | Force between charges in a medium | Quantisation of charge MCQ |
| 2023 | Dipole in a uniform field (5) | Linear charge density on a wire | Coulomb's law SI unit MCQ |
| 2022 | Gauss's law for a charged shell (3) | Superposition of three charges | Field-line property |
| 2021 | Field due to a point charge (2) | Dipole in a non-uniform field | Field due to a point charge |
How to Revise Electric Charges and Fields in 2 Hours
Use this four-slot plan the night before the exam.
- 0 to 30 min: Charge properties and Coulomb's law. Solve two superposition numericals.
- 30 to 60 min: Electric field, field lines and both dipole derivations.
- 60 to 90 min: Flux and Gauss's law for wire, sheet and shell. Sketch each Gaussian surface.
- 90 to 120 min: Flush through the formula table and the 7-derivation index.
Other Resources for Class 12 Physics Chapter 1
Pair these notes with the Solutions, Handwritten Notes, Formula Sheet and official NCERT chapter below.
| Resource | What it covers | Open |
|---|---|---|
| Notes | Typed revision notes for the full chapter. | You are here |
| NCERT Solutions | Step-by-step answers to every exercise question. | Chapter 1 NCERT Solutions |
| Handwritten Notes | Scanned notebook pages for last-mile revision. | Chapter 1 Handwritten Notes |
| Formula Sheet | All formulas with full derivations. | Chapter 1 Formula Sheet |
| NCERT Book PDF | Official NCERT textbook chapter. | Chapter 1 NCERT Book PDF |
All Chapters Notes for Class 12 Physics
| Chapter | Notes link |
|---|---|
| Chapter 1 | Electric Charges and Fields (you are here) |
| Chapter 2 | Electrostatic Potential and Capacitance Notes |
| Chapter 3 | Current Electricity Notes |
| Chapter 4 | Moving Charges and Magnetism Notes |
| Chapter 5 | Magnetism and Matter Notes |
| Chapter 6 | Electromagnetic Induction Notes |
| Chapter 7 | Alternating Current Notes |
| Chapter 8 | Electromagnetic Waves Notes |
| Chapter 9 | Ray Optics and Optical Instruments Notes |
| Chapter 10 | Wave Optics Notes |
| Chapter 11 | Dual Nature of Radiation and Matter Notes |
| Chapter 12 | Atoms Notes |
| Chapter 13 | Nuclei Notes |
| Chapter 14 | Semiconductor Electronics Notes |
Class 12 Physics Chapter 1 Electric Charges and Fields Notes FAQs
Ques. What are the main topics in the Class 12 Physics Chapter 1 notes?
Ans. The notes cover electric charge and its properties, Coulomb's law in vector form, the superposition principle, electric field and field lines, the electric dipole, electric flux, Gauss's law (infinite line, plane sheet, spherical shell), and continuous charge distributions.
Ques. What is the weightage of Electric Charges and Fields in Class 12?
Ans. The chapter carries about 6 marks in the CBSE Class 12 Physics board paper, 4 to 5 percent in JEE Main, and 1 to 2 questions a year in NEET. Most marks sit in the Gauss's law and dipole derivations.
Ques. What is Coulomb's law?
Ans. The electrostatic force between two point charges is proportional to the product of charges and inversely proportional to the square of the distance: F = k q₁q₂ / r², with k = 9 × 10⁹ N m² / C². Like charges repel, unlike charges attract.
Ques. What is Gauss's law?
Ans. The total electric flux through any closed surface equals the enclosed charge divided by ε₀, that is ∮ E·dA = qenc / ε₀. It is most useful when the charge distribution has linear, planar, or spherical symmetry.
Ques. Where can I download the Class 12 Physics Chapter 1 notes PDF?
Ans. The PDF is on this page via the download card at the top. It covers all formulas, the 5 field-line properties, and the 7-derivation index, and follows the 2026-27 NCERT syllabus.
Comments