Flux through a Sphere: Finding the Flux of a Vector Field Across a Unit Sphere

In summary, the flux of the vector field F(x,y,z)=(z,y,x) across the unit sphere x^2+y^2+z^2=1 can be found by using the divergence theorem, which gives the correct answer of 4(pi)/3. Alternatively, the flux can also be found by calculating the triple integral of 1 over the volume enclosed by the sphere, which also results in the correct answer of 4(pi)/3. Spherical coordinates can be used, but are not necessary for this problem.
  • #1
pivoxa15
2,255
1

Homework Statement


Find the flux of the vector field F(x,y,z)=(z,y,x) across the unit sphere x^2+y^2+z^2=1



The Attempt at a Solution


My Answer: 3(pi)^2/8

Book answer: 4(pi)/3
 
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  • #2
The easy way to do this is to use the divergence theorem which immediately gives you the book answer.
 
  • #3
The book answer is correct. Can you show your work?
 
  • #4
divergence theorem: triple integral of the divergence of the vector field, in this case the divergence is just 1, so you're just essentially finding the volume of the sphere
 
  • #5
RIght, I just had problems with the surface integral but it's just d(theta)d(psi)

by letting x=theta, y=psi so the jacobian is 1.

All correct?
 
  • #6
yes but no need for spherical coordinates since its just the triple integral:

SSS1dV = volume of sphere over the domain d = { (x,y,z): x^2 + y^2 + z^2 = 1 }
( sorry no latex )
 
  • #7
If dexter still posted regularly, I'm sure he would have made a point to say Volume *enclosed by* the sphere =] Welcome to PF Dmak! (And don't mind that comment, really just semantics).

EDIT: Wow Dick has 2^(12) posts =]
 
Last edited:
  • #8
Dmak said:
yes but no need for spherical coordinates since its just the triple integral:

SSS1dV = volume of sphere over the domain d = { (x,y,z): x^2 + y^2 + z^2 = 1 }
( sorry no latex )


In the first attempt, I wasn't trying to use the divergence theorem but the surface integrable dS. It was the long way but I wanted to know that I could do it.
 
  • #9
Gib Z said:
If dexter still posted regularly, I'm sure he would have made a point to say Volume *enclosed by* the sphere =] Welcome to PF Dmak! (And don't mind that comment, really just semantics).

EDIT: Wow Dick has 2^(12) posts =]



haha thanks Gib_Z :p
 

1. What is flux through a sphere?

Flux through a sphere is a measure of the amount of flow or movement of a vector field through the surface of a sphere. It is a concept used in physics and engineering to understand the flow of various physical quantities, such as electric or magnetic fields, through a three-dimensional space.

2. How is flux through a sphere calculated?

The flux through a sphere can be calculated using the formula F = ∫∫S F · dS, where F is the vector field, S is the surface of the sphere, and dS is the differential element of the surface. This integral represents the summation of all the vector field values at each point on the surface, taking into account the direction and magnitude of the field at that point.

3. What factors affect the flux through a sphere?

The flux through a sphere is affected by the strength and direction of the vector field, the size and shape of the sphere, and the orientation of the sphere with respect to the field. It is also affected by any obstacles or boundaries present in the field that may cause disruptions or changes in the flow.

4. How is flux through a sphere related to Gauss's law?

The concept of flux through a sphere is closely related to Gauss's law, which states that the total electric flux through a closed surface is equal to the enclosed charge divided by the permittivity of free space. This means that the flux through a sphere can be calculated using the electric field and the charge enclosed within the sphere.

5. What are some real-world applications of flux through a sphere?

The concept of flux through a sphere has many practical applications in fields such as engineering, physics, and meteorology. It is used in the design of electrical circuits, the study of weather patterns, and the analysis of fluid flow in pipes and channels. It is also used in medical imaging techniques, such as MRI, to understand the flow of fluids or particles within the body.

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