Outward Flux Problem: Showing k4\pi & 0 for Domain D in R3

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In summary, the outward flux over the boundary surface S of a "nice" bounded domain D in R3 with a vector field F = -k del(1/r) is k4\pi if the origin is located inside D, and 0 if the origin is outside D or S. This can be calculated using Gauss' Theorem and taking into account the direction of the unit vector in the direction of (x,y,z).
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Treadstone 71
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Let D be a "nice" bounded domain in R3 with boundary surface S and let F =-k del(1/r). Show that the outward flux over S is [tex]k4\pi[/tex] if the origin lies in D and 0 if the origin lies outside D U S.

I don't understand the notation for F. What is del of 1/r?
 
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Can anyone help?
 
  • #3
Del is just a notation for the gradient operator. The vector field is [tex] - k \vec{\nabla}\left(\frac{1}{r}\right) = k \frac{1}{r^2}\hat{r} [/tex].

As for your problem, use Gauss' Theorem to calculate the integral. Be very careful when your surface encloses the origin.
 
  • #4
By [tex]\hat{r}[/tex], you mean the unit vector in the direction of (x,y,z)?
 
  • #5
Yes, [tex] \hat{r} = \frac{\vec{r}}{r} [/tex].
 

FAQ: Outward Flux Problem: Showing k4\pi & 0 for Domain D in R3

What is the Outward Flux Problem?

The Outward Flux Problem is a mathematical problem that involves finding the amount of fluid or energy flowing out of a three-dimensional region, or domain, in space. It is often used in physics and engineering to analyze the flow of fluids, such as air or water, through a specific area.

How is the Outward Flux calculated?

The Outward Flux is calculated by taking the dot product of the vector field and the outward pointing normal vector at each point on the surface of the domain. This is then integrated over the entire surface to obtain the total amount of flux.

What is k4π in the context of the problem?

k4π is a constant that represents the surface area of a unit sphere in three-dimensional space. It is often used in the Outward Flux Problem to show the total flux through a closed surface, as it is equal to the surface area of the entire domain.

What does the value 0 represent in the solution for the Outward Flux Problem?

In the context of the Outward Flux Problem, the value 0 often represents a closed or isolated surface, meaning there is no net flow of fluid or energy through the domain. This could also indicate that the vector field is perpendicular to the surface, resulting in a dot product of 0 and therefore, no flux.

What is the significance of the domain D in R3?

The domain D in R3 represents the three-dimensional region in which the Outward Flux Problem is being solved. It is often used to define the boundaries of the domain and is essential in calculating the total flux through the surface. The domain can be any shape, as long as it is a closed surface in three-dimensional space.

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