Surface Integrals: Why Dot ds with Normal?

In summary, when performing surface integrals, the area element ds is dotted with the normal in order to determine the flux of the vector field through the surface being integrated over. This is because the dot product considers only the component of the field that is perpendicular to the surface at each point.
  • #1
likephysics
636
2

Homework Statement


This is not a HW prob. Just a question.
When doing surface integrals, why should the area element ds be dotted with the normal. I don't get it .
[tex]\oint[/tex]A.n ds

Homework Equations





The Attempt at a Solution

 
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  • #2
likephysics said:

Homework Statement


This is not a HW prob. Just a question.
When doing surface integrals, why should the area element ds be dotted with the normal. I don't get it .
[tex]\oint[/tex]A.n ds

It doesn't have to be, in general. There are other types of surface integrals as well. The type you've listed above is designed to determine the flux of the vector field A through the surface you are integrating over. The dot product is there because, by definition of flux, you are only concerned with the component of A that is perpendicular to the surface at each point on the surface.
 
  • #3
Ok. Thanks. I can live with it now.
 

Related to Surface Integrals: Why Dot ds with Normal?

1. What is a surface integral?

A surface integral is a type of mathematical calculation used to find the total value of a function over a given surface. It involves integrating the product of the function and a differential element that represents the surface area, such as dot ds with normal.

2. What is the significance of using dot ds with normal in surface integrals?

The dot ds with normal is a crucial component in surface integrals because it helps to determine the orientation of the surface. This information is necessary for accurately calculating the surface integral.

3. How is dot ds with normal calculated in surface integrals?

Dot ds with normal is calculated by taking the dot product of two vectors: the unit vector normal to the surface (ds) and the differential element representing the surface area (ds). This calculation gives the magnitude of the surface element in a specific direction.

4. What is the difference between surface integrals and line integrals?

The main difference between surface integrals and line integrals is the shape of the integration path. In surface integrals, the path is a two-dimensional surface, while in line integrals, the path is a one-dimensional curve.

5. How are surface integrals used in scientific research?

Surface integrals are used in various fields of science, such as physics, engineering, and mathematics, to calculate physical quantities, such as flux, electric potential, and work done. They are also used to solve problems involving surfaces, such as finding the center of mass or determining the surface area of a three-dimensional object.

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