Ch 1 introduces electrostatics — properties of charges, Coulomb's law, electric field, electric field lines, dipole, and Gauss's law for symmetric charge distributions.
Coulomb's law: F = kq₁q₂/r² (k = 9 × 10⁹). Superposition: net force = vector sum of individual forces. Electric field E = F/q₀ (N/C). E due to point charge: E = kq/r². E due to dipole: along axis E = 2kp/r³, along equatorial E = kp/r³. Field lines: start from +, end at −, never cross.
Electric flux Φ = ∫E·dA. Gauss's law: total flux through a closed surface = q_enclosed/ε₀. Applications: E of infinite line charge (λ/2πε₀r), infinite plane (σ/2ε₀), sphere (like point charge outside, zero inside conductor). Powerful for symmetric geometries.
Download: https://ncert.nic.in/textbook/pdf/leph101.pdf | Part I: https://ncert.nic.in/textbook/pdf/leph1ps.zip
In electrostatic equilibrium, free electrons redistribute so that the net electric field inside is zero. If there were a field, charges would move (contradicting equilibrium). All excess charge resides on the surface, and the field just outside is perpendicular to the surface.
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