Why is the electric field inside a conductor zero when it is placed in an external electric field?
**Superposition principle** asserts net Coulomb force on charge equals vector sum of forces from each other charge independently, F_net = Σ F_i, where F_i = k q q_i/r_i² r̂_i. In equilateral triangle or square symmetry, components may cancel at centroid, producing equilibrium. In a conductor, free charges redistribute in response to an external field until the internal field cancels the external field completely. This equilibrium condition ensures no net field exists inside, as any field would cause charge motion, violating static conditions. Substituting values gives Charge redistribution, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.
Ref: NCERT > Physics Book > Electric Charges and Fields > Superposition Principle and Equilibrium of Charges