A uniform electric field exists in space. Find the flux of this field through a cylindrical surface with the axis parallel to the field.

Explanation

Consider figure and take a small area `Delta S` on the cylinderical surface. The normal to this area will be perpendicular to the axis of the cylinder. But the electric field is parallel t o the axis and henc
`Delta Phi = vec(E)*vec(S) = E Delta vec(S) = E Delta S cos (pi//2) =0`
This is true for each small part of the cylinderical surface. Summing over the entire surface. the total flux is zero.