Practice question

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. Electric field at midpoint: E₁ = 9 × 10⁹ × (3 × 10⁻⁶/(0.075)²) = 4.8 × 10⁶ N/C (towards -3 μC ). E₂ = 4.8 × 10⁶ N/C (towards -3 μC ). Net E = 4.8 × 10⁶ + 4.8 × 10⁶ = 9.6 × 10⁶ N/C . Force: F = q E = 2 × 10⁻⁶ × 9.6 × 10⁶ = 19.2 N . Substituting values gives 19.2