Integrating Vector Fields: Volume vs. Surface

In summary, the given equation states that the left hand side is the integral of the vector field A over a volume, while the right hand side is the integral of A over a closed surface. The surface element is represented by dS, which should be a vector surface element and is calculated using the parameterization of the surface.
  • #1
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Homework Statement



[tex]\int[/tex] delxA dv = -[tex]\oint[/tex] Axds

where A is a vector field
Left hand side is integral over volume. Right hand side is integral over closed surface.

Homework Equations





The Attempt at a Solution



Can't understand what Axds means.
 
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  • #2
A is the vector field
and dS is the closed surface on which you want to see the flux
x is a multiplication symbol
 
  • #3
Presumably what you are calling ds (which is usually used for an element of arc length) should be the vector surface element. If the surface is parameterized as

[tex]\vec R = \vec R(u,v) = \langle x(u,v),y(u,v),z(u,v)\rangle[/tex]

the surface element is

[tex]d\vec S = \vec R_u \times \vec R_v\, dudv[/tex]
 

FAQ: Integrating Vector Fields: Volume vs. Surface

What is the difference between integrating a vector field over a volume and over a surface?

Integrating a vector field over a volume involves calculating the total flux or flow of the vector field through a three-dimensional region. On the other hand, integrating over a surface involves calculating the flux or flow of the vector field through a two-dimensional surface. In simpler terms, volume integration looks at the overall effect of the vector field within a three-dimensional space, while surface integration looks at the effect on a two-dimensional surface.

How is the integration process different for volume and surface integrals?

The integration process for volume and surface integrals is different due to the different dimensions involved. For volume integrals, we use a triple integral to integrate over three dimensions, while for surface integrals, we use a double integral to integrate over two dimensions. Additionally, the limits of integration are also different for the two types of integrals.

When would you use volume integration instead of surface integration?

Volume integration is typically used when we want to find the total effect of a vector field within a three-dimensional region. This could include finding the total electric charge within a volume, or the total amount of fluid flowing through a three-dimensional pipe. Surface integration, on the other hand, is used when we want to find the effect of a vector field on a two-dimensional surface, such as the force exerted by a fluid on a flat surface.

Can volume and surface integrals be used interchangeably?

No, volume and surface integrals cannot be used interchangeably. They represent different concepts and have different mathematical formulas and limits of integration. While it is possible to convert a volume integral into a surface integral using the Divergence Theorem, this is not always applicable and should be used with caution.

How are volume and surface integrals related to each other?

Volume and surface integrals are related through the Divergence Theorem, which states that the volume integral of the divergence of a vector field is equal to the surface integral of the vector field itself. This means that we can convert a volume integral into a surface integral and vice versa, under certain conditions. This theorem is also known as the Gauss's Theorem in three dimensions.

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