Modul
e
17 : Surfaces, Surface Area, Surface integrals, Divergence Theorem and applications
Lecture
50 : Application of surface integrals [Section 50.2]
Similarly for
, the outward unit normal is
Thus,
Hence
50.2.8
Note:
(i)
Note that for an orientable surface, if
is one choice of continuous unit normal vector to
, then
is also another choice of continuous unit normal to
. The flux integral changes sign if we change
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, the outward unit normal is 
is one choice of continuous unit normal vector to 
, then
is also another choice of continuous unit normal to 
. The flux integral changes sign if we change
