Electric flux is defined as the total number of electric lines of force crossing a surface in a direction normal to that surface. Mathematically, it can be expressed using the integral form: Φ = ∫E·dS cos(θ), where E represents the electric field intensity, dS is an infinitesimal area vector on the surface, and θ is the angle between them. For closed surfaces enclosing charges (q1, q2,...), Gauss's law states that total flux equals 1/ε₀ times net enclosed charge: Φ = Σ(q)/ε₀.