Practice question

**Vector addition of forces** underlies multi-charge analysis. Each pair contributes independent Coulomb force, resultant obtained by resolving components along axes. Equilibrium occurs when vector sum vanishes, often at symmetric points where contributions balance. Insulators lack free charges that can move to cancel an external field. Unlike conductors, where mobile electrons redistribute, insulators’ fixed charges allow the field to penetrate, as no shielding mechanism exists. Substituting values gives Absence of free charges, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.