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) , k = (1/4 π ε₀) = 9 × 10⁹ , so (1/ε₀) = 4 π × 9 × 10⁹ . E = (2 × 10⁻⁶/2 π × 8.854 × 10⁻¹² × 0.05) = 7.19 × 10⁵ N/C . Or, E = (2kλ/r) = (2 × 9 × 10⁹ × 2 × 10⁻⁶/0.05) = 7.2 × 10⁵ N/C . Substituting