Just outside a large uniformly-charged conducting sheet with surface charge density σ, the magnitude of the electric field is:

1. For a CONDUCTOR, charge lies on the surface and E inside conductor = 0. 2. Pillbox Gaussian surface gives E · A = σ A / ε₀ ⇒ E_outside = σ / ε₀. 3. For an isolated non-conducting (insulating) sheet, both sides have E = σ / (2 ε₀). _Source: syllabus Physics Ch 1 §1.10 Gauss in a Conductor vs Sheet_