Practice question

**Gauss's law** Φ = ∮ E·dA = q_enc/ε₀ is fundamental relation between flux and enclosed charge. For charge at centre of cube, total flux = q/ε₀ distributes equally over six faces, each receiving Φ/6, but total remains q/ε₀ irrespective of cube edge. Flux through face at x = 0 : Φ = E × A = 5 × 10³ × (0.3)² = 450 N·m²/C (inward). Flux through face at x = 0.3 : 450 N·m²/C (outward). Net flux: 450 - 450 = 0 N·m²/C (no charge enclosed). Substituting values gives 0 N·m²/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.