Greens theorem direction of line integral

In summary, Green's theorem states that a closed line integral can be transformed into a surface integral. The direction of the line integral is important because it determines the direction of the surface and can result in a negative value if changed. This concept is also seen in Stoke's theorem, where the direction of the path integral is determined by the direction of the normal to the surface. This highlights the importance of considering the direction in these types of integrals.
  • #1
SpartanG345
70
1
My course notes said that in greens theorem

where the closed line integral of F.r = the double integral (...)dxdy

the curve c is taken once anti-clockwise, why does it matter which way you take the line integral? Does it matter at all?

Thanks
 
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  • #2
Green theorem tells that we can transform a closed line integral of curl to a surface integral. As we know, the curl of a vector will still be a vector, so the line integral of curl will have its direction, and it points to the direction of the surface. So if you change the circular as a clockwise one, the direction will change, and you will obtain a minus.
 
  • #3
Note that in Stoke's theorem, which generalizes Green's theorem to the boundary of a surface in three dimensions, the direction of the path integral dependes upon the direction the normal to the surface points. For example, if you surface is a sphere, whether the normal is pointing inward or outward. As ben.zhang98 said, changing the the direction changes the sign.
 

1. What is Green's theorem?

Green's theorem is a mathematical tool used in vector calculus to relate a line integral around a simple closed curve to a double integral over the region enclosed by the curve. It is named after the mathematician George Green and is also known as the Gauss-Green theorem or the divergence theorem in two dimensions.

2. What is the direction of a line integral in Green's theorem?

The direction of a line integral in Green's theorem is determined by the orientation of the curve. The direction is counterclockwise if the curve is traversed in the direction of increasing values of the independent variable, and clockwise if the curve is traversed in the direction of decreasing values of the independent variable.

3. How is Green's theorem used in science?

Green's theorem is used in various scientific fields, such as physics and engineering, to calculate the work done by a force, the flow of a fluid, or the circulation of a vector field. It is also used in the study of electromagnetism and fluid dynamics.

4. What is the significance of the direction of a line integral in Green's theorem?

The direction of a line integral in Green's theorem is significant because it determines the sign of the resulting value. If the direction is counterclockwise, the value will be positive, and if the direction is clockwise, the value will be negative. This helps in determining the direction of energy flow or fluid circulation in a given system.

5. Can Green's theorem be extended to higher dimensions?

Yes, Green's theorem can be extended to higher dimensions through the use of the generalized Stokes' theorem. In three-dimensional space, it becomes the divergence theorem, while in four-dimensional space, it becomes the generalized Stokes' theorem. These higher-dimensional versions are used in advanced mathematics and physics, such as in the study of fluid dynamics and Einstein's field equations in general relativity.

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