Practice question

**Measure of field penetration** depends on both magnitude and projected area. Understanding angle between E and normal vector is crucial, flux zero when field parallel to surface, maximum when perpendicular. Area vector Δ S = (0.15)² = 0.0225 m² along z-axis. Flux: Φ = E · Δ S = 4 × 10³ × 0.0225 = 90 N·m²/C . Substituting values gives 90 N·m²/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.