Electric flux related to perpendicular suf??? Hello. This is my first in here. I am studying on Physics electricity and magnetism. While I am reading the concept of electric flux, the textbook repeatly mention about "perpendicular to the surface" . Why is the perpendicular surface important? Here is the one of the paragraph from the book. "For a sphere centered on the point charge Q, the flux is just this product pi=EA=Q/e0, as introduced in the expression for Coulmb's law above. This expressition pi is correct in this case because the electric field at the surface is always perpendicular to the surface and its magnitude is the same at all points on the surface." Thanks.