Difference between revisions of "Stokes' Theorem"
(better intro) |
(improved) |
||
| Line 6: | Line 6: | ||
Stokes' Theorem is useful in calculating [[circulation]] in mechanical engineering. A [[conservative field]] has a circulation (line integral on a simple, closed curve) of zero, and application of the Stokes' Theorem to such a field proves that the curl of a conservative field over the enclosed surface must also be zero. | Stokes' Theorem is useful in calculating [[circulation]] in mechanical engineering. A [[conservative field]] has a circulation (line integral on a simple, closed curve) of zero, and application of the Stokes' Theorem to such a field proves that the curl of a conservative field over the enclosed surface must also be zero. | ||
| + | |||
| + | == General Form == | ||
In its most general form, this theorem is the fundamental theorem of [[Exterior Calculus]], and is a generalization of the [[Fundamental Theorem of Calculus]]. It states that if ''M'' is an oriented piecewise smooth [[manifold]] of [[dimension]] k and <math>\omega</math> is a smooth (''k''−1)-[[differential form|form]] with compact support on ''M'', and ∂''M'' denotes the boundary of ''M'' with its induced orientation, then | In its most general form, this theorem is the fundamental theorem of [[Exterior Calculus]], and is a generalization of the [[Fundamental Theorem of Calculus]]. It states that if ''M'' is an oriented piecewise smooth [[manifold]] of [[dimension]] k and <math>\omega</math> is a smooth (''k''−1)-[[differential form|form]] with compact support on ''M'', and ∂''M'' denotes the boundary of ''M'' with its induced orientation, then | ||
| Line 29: | Line 31: | ||
Here S is a surface, E is the boundary path of S, and the single integral denotes path integration around E with <math>\vec{\mathrm{d}l}</math> as the length element. The <math>\nabla \times</math> on the left side is the [[curl]] operator. | Here S is a surface, E is the boundary path of S, and the single integral denotes path integration around E with <math>\vec{\mathrm{d}l}</math> as the length element. The <math>\nabla \times</math> on the left side is the [[curl]] operator. | ||
| − | These last two examples (and Stokes' theorem in general) are | + | These last two examples (and Stokes' theorem in general) are are the subject of vector calculus. They play important roles in [[electrodynamics]]. The divergence and curl operations are cornerstones of [[Maxwell's Equations]]. |
| − | Stokes' Theorem is a lower-dimension version of the Divergence Theorem, and a higher-dimension version of [[Green's Theorem]]. Green’s Theorem relates a line integral to a double integral over a region, while Stokes' Theorem relates a | + | Stokes' Theorem is a lower-dimension version of the Divergence Theorem, and a higher-dimension version of [[Green's Theorem]]. Green’s Theorem relates a line integral to a double integral over a region, while Stokes' Theorem relates a surface integral of the curl of a function to its line integral. |
[[Category:vector analysis]] | [[Category:vector analysis]] | ||
[[Category:calculus]] | [[Category:calculus]] | ||
[[Category:Mathematics]] | [[Category:Mathematics]] | ||
[[Category:Physics]] | [[Category:Physics]] | ||
Revision as of 17:31, January 3, 2010
Stokes' Theorem expresses the surface integral of the curl of vector field in terms of its easier-to-compute circulation:
This is an extension of Green's Theorem to surface integrals, and is also the analog in two dimensions of the Divergence Theorem.
Stokes' Theorem is useful in calculating circulation in mechanical engineering. A conservative field has a circulation (line integral on a simple, closed curve) of zero, and application of the Stokes' Theorem to such a field proves that the curl of a conservative field over the enclosed surface must also be zero.
General Form
In its most general form, this theorem is the fundamental theorem of Exterior Calculus, and is a generalization of the Fundamental Theorem of Calculus. It states that if M is an oriented piecewise smooth manifold of dimension k and 
is a smooth (k−1)-form with compact support on M, and ∂M denotes the boundary of M with its induced orientation, then
,
where d is the exterior derivative.
There are a number of well-known special cases of Stokes' theorem, including one that is referred to simply as "Stokes' theorem" in less advanced treatments of mathematics, physics, and engineering:
- When k=1, and the terms appearing in the theorem are translated into their simpler form, this is just the Fundamental Theorem of Calculus.
- When k=3, this is often called Gauss' Theorem or the Divergence Theorem and is useful in vector calculus:
Where R is some region of 3-space, S is the boundary surface of R, the triple integral denotes volume integration over R with dV as the volume element, and the double integral denotes surface integration over S with 
as the oriented normal of the surface element. The 
on the left side is the divergence operator, and the 
on the right side is the vector dot product.
- When k=2, this is often just called Stokes' Theorem:
Here S is a surface, E is the boundary path of S, and the single integral denotes path integration around E with 
as the length element. The 
on the left side is the curl operator.
These last two examples (and Stokes' theorem in general) are are the subject of vector calculus. They play important roles in electrodynamics. The divergence and curl operations are cornerstones of Maxwell's Equations.
Stokes' Theorem is a lower-dimension version of the Divergence Theorem, and a higher-dimension version of Green's Theorem. Green’s Theorem relates a line integral to a double integral over a region, while Stokes' Theorem relates a surface integral of the curl of a function to its line integral.
