Practice question

**Inverse-square law** for charges states F ∝ 1/r² while increasing with charge product. Using k = 9×10⁹ N·m²/C², force at distance r follows F = k q₁q₂/r², forming basis for pairwise force calculation. Negative charge indicates electrons gained. q = n e , e = -1.6 × 10⁻¹⁹ C . n = (q/|e|) = (9.6 × 10⁻⁸/1.6 × 10⁻¹⁹) = 6 × 10¹¹ . Substituting values gives 6 × 10¹¹, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.