Practice question

**Electric flux** through surface measures field lines crossing it, Φ = E·A = E A cosθ for uniform field, unit N·m²/C. For circular area in xy-plane with field along z, θ = 0°, cosθ = 1, so Φ = E·πR² directly, maximum when field normal to surface. Total flux: Φ = (q/ε₀) = (4 × 10⁻⁶/8.854 × 10⁻¹²) = 4.52 × 10⁵ N·m²/C . Flux through one face (cube has 6 faces): Φfₐcₑ = (Φ/6) = (4.52 × 10⁵/6) = 7.53 × 10⁴ N·m²/C . Substituting values gives 7.5 × 10⁴ N·m²/C, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.