Practice question

**Charge density formulation** allows integration over extended bodies, but highly symmetric cases yield simple expressions. Infinite line gives E ∝ λ/r, unlike point charge 1/r², reflecting different geometry of source. Surface area: A = 4 π r² = 4 π (0.17)² = 0.1156 π m² . Charge: q = sigma A = 15 × 10⁻⁶ × 0.1156 π = 5.45 × 10⁻⁶ C . Substituting values gives 5.45 × 10⁻⁶ C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.