Electric Flux Through Surface

Electric flux Φ = ∫ E⃗·dA⃗ measures the number of field lines crossing a surface.

For uniform E: Φ = EA cosθ, where θ is the angle between E⃗ and area normal n̂.

Maximum when n̂ ∥ E⃗ (θ=0), zero when perpendicular (θ=90°).