Physics XI - Chapter 1: Physical World
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- Charge Quantization: Q = ±ne, where n is an integer and e = 1.6 × 10⁻¹⁹ C.
- Charge Conservation: Total charge in an isolated system remains constant.
- Coulomb's Law: F = (1/(4πε₀)) × (q₁q₂/r²); electrostatic force between two point charges.
- Electric Field (E): E = F/q₀; force per unit positive test charge. Vector quantity with SI unit N/C.
- Electric Field due to Point Charge: E = (1/(4πε₀)) × (q/r²) along radial direction.
- Electric Dipole Moment (p): p = q × 2a (magnitude); direction from -q to +q.
- Torque on Dipole: τ = pE sinθ in uniform electric field.
- Gauss's Law: Φ = ∮E·dA = Q_enclosed/ε₀; relates electric flux to enclosed charge.
- Electric Flux: Φ = E·A = EA cosθ; number of field lines passing through a surface.
- Field due to Infinite Line Charge: E = λ/(2πε₀r) ∝ 1/r.
- Field due to Infinite Sheet: E = σ/(2ε₀); constant and perpendicular to sheet.
- Field inside Conductor: Zero in electrostatic equilibrium.
- Permittivity of Free Space: ε₀ = 8.85 × 10⁻¹² C²/N·m².
- Electrostatic Constant: 1/(4πε₀) = 9 × 10⁹ N·m²/C².
Basic Level Questions
Chapter Summary
Electric Charges and Fields forms the foundation of electrostatics, introducing fundamental concepts that govern the behavior of charged particles. The chapter begins with the basic properties of electric charges - quantization, conservation, and additive nature. Coulomb's Law provides the mathematical framework for calculating electrostatic forces between point charges, while the concept of electric field helps visualize the influence of charges in space.
Key applications include the study of electric dipoles, their behavior in uniform electric fields, and the calculation of electric fields due to various charge distributions using both Coulomb's Law and Gauss's Law. The latter offers a powerful method for determining electric fields in symmetric configurations. The chapter also covers important practical concepts like electric flux, conductors in electrostatic equilibrium, and the behavior of charges on conductor surfaces.
Mastery of these fundamental principles is essential for understanding more advanced topics in electromagnetism, including electric potential, capacitance, and current electricity that follow in subsequent chapters.