Practice question

**Line charge concept** extends point charge to infinite wire where symmetry dictates radial field proportional to λ and inversely proportional to distance r. λ = q/L for uniform case, field direction depends on sign of λ, outward for positive. E = (λ/2 π ε₀ r) , or E = (2 k λ/r) , k = 9 × 10⁹ N·m²/C² . 1.8 × 10⁵ = (2 × 9 × 10⁹ × λ/0.03) . λ = (1.8 × 10⁵ × 0.03/18 × 10⁹) = 3 × 10⁻⁷ C/m . Substituting values gives 3.0 × 10⁻⁷ C/m, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and