Practice question

**Flux definition** Φ = ∮ E·dA links field to area orientation. For uniform E perpendicular to surface, Φ = E A, with A = πr² for circle. Inclination reduces flux by cosθ factor, sign indicating outward or inward crossing. Area: A = 0.15 × 0.2 = 0.03 m² . Flux: Φ = E A cos 0° = 9 × 10³ × 0.03 = 270 N·m²/C . Substituting values gives 270 N·m²/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.