the area element. Notice we could look at the expression E Δ S cos θ in two ways: E ( Δ S cos θ ) i.e., E times the FIGURE . Dependence of flux on the inclination θ between E and ˆ n . FIGURE .
Convention for defining normal ˆ n and Δ S. * It will not be proper to say that the number of field lines is equal to E Δ S . The number of field lines is after all, a matter of how many field lines we choose to draw. What is physically significant is the relative number of field lines crossing a given area at different points.