The ebook Elementary Calculus is based on material originally written by H.J. Keisler. For more information please read the copyright pages.


Gauss' Theorem

We are now ready to state Gauss' Theorem.

GAUSS' THEOREM

Given a vector field F(x, y, z) and a solid region E,

13_vector_calculus-342.gif

This equation may also be written in the form

13_vector_calculus-343.gif

Gauss' Theorem is sometimes called the Divergence Theorem.

For fluid flow, Gauss' Theorem states that the outward rate of flow across the boundary of E is equal to the integral of the divergence over E (Figure 13.6.9). As in the two-dimensional case, the divergence is the rate at which the density is decreasing.

13_vector_calculus-344.gif

Figure 13.6.9

The following corollary is another analogue of the Path Independence Theorem.

COROLLARY 3

If F(x, y, z) has continuous second partials, the surface integral of curl F over the boundary of E is zero. In symbols,

13_vector_calculus-345.gif

PROOF

Since div(curl F) = 0,

13_vector_calculus-346.gif


Last Update: 2006-11-22