Practice question

**Line charge concept** extends point charge to infinite wire where symmetry dictates radial field proportional to λ and inversely proportional to distance r. λ = q/L for uniform case, field direction depends on sign of λ, outward for positive. The field depends only on the surface charge density ( sigma/2ε₀ ), as derived from Gauss’s law for an infinite plane. The material affects charge distribution, but for a given sigma , the field is universal, assuming infinite extent and uniformity. Substituting values gives Surface charge density, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.