Electric Charges & Fields
স্থির তড়িৎ: আধান ও ক্ষেত্র
Coulomb's inverse square law, superposition principle, electric field vectors, electric field lines, electric dipole dynamics, and Gauss's law applications.
Target Learning Objectives
- Apply Coulomb's law in vector form for multiple point charge distributions.
- Compute electric field intensities for linear, surface, and volume charge distributions.
- Derive torque and potential energy of an electric dipole in uniform external fields.
- State Gauss's Law and evaluate electric field around infinite wires, sheets, and spherical shells.
Governing Physical Concepts
- Quantization & Conservation of Electric Charge
- Coulomb's Law Vector Form: F = (1 / 4πε0) (q1 q2 / r^2) r̂
- Electric Dipole Moment (p = q × 2a) & Torque (τ = p × E)
- Gauss's Law Flux Integral: ∮ E · dA = q_enclosed / ε0
- Field of Uniformly Charged Spherical Shell (Inside & Outside)
Chapter Topics & Breakdown
Coulomb's Law & Principle of Superposition
Electrostatic forces between point charges in vacuum and dielectric media.
Electric Field Intensity & Field Line Properties
Concept of electric field vectors, continuous charge field integrals, and field line geometry.
Electric Dipole: Axial, Equatorial Field & Torque
Dipole moment vector, field calculations, and torque in uniform external fields.
Electric Flux & Gauss's Theorem
Evaluation of surface flux integrals and fundamental proof of Gauss's Law.
Standard Applications of Gauss's Theorem
Fields of infinitely long charged wire, infinite planar sheet, and uniformly charged spherical shell.
Study Materials for this Chapter
Electrostatics & Potential: Master Formula Sheet
High-density mathematical compendium compiling Coulomb's law, Gauss's law flux formulas, dipole fields, capacitance theorems, and energy densities.
Class XII Physics: Complete Board Standard Model Examination Paper
Full-length board-standard theory paper reflecting higher secondary physics examination structure, choice options, and step scoring.
Quick Revision Summary
“Electric field inside a uniformly charged conducting shell or conductor in electrostatic equilibrium is identically zero.”
- •Dipole field along axial line: E_axial ≈ 2kp/r^3; equatorial line: E_equatorial ≈ kp/r^3.
- •Electric flux depends only on enclosed charge, independent of Gaussian surface geometry.
- •Work done by electrostatic force along any closed path is zero (conservative field).
Structured Practice Roadmap
Comprehensive problem sets covering vector Coulomb equilibrium, dipole torque, and Gauss's law flux calculations.
Board Diagnostic 01: Electrostatics
Assessment Architecture • Academic Evaluation SpecificationStructured test with standard board derivations and numerical problems.