Proving: \int\textbf{B}\cdot\textbf{H}d^{3}x=0

  • Thread starter Old Guy
  • Start date
In summary, The task is to prove that the integral of the dot product of magnetic field and magnetic field intensity over a region in space is equal to zero, given that there is no current density. The attempt at a solution involves using a vector identity and the divergence theorem, but the specific surface and values for the magnetic field and magnetic flux are not specified. There is a suggestion to use Ampere's law, but it is not applicable in this case.
  • #1
Old Guy
103
1

Homework Statement


Prove [tex]\int\textbf{B}\cdot\textbf{H}d^{3}x=0[/tex]. There is no current density.



Homework Equations




The Attempt at a Solution

Through a vector identity and the divergence theorem, I get
[tex]\oint\Phi_{M}\textbf{B}\cdot{d}\textbf{a}[/tex] but don't know how to proceed. This seems close to Ampere's law with no enclosed current, but not quite.
 
Physics news on Phys.org
  • #2
What surface are you integrating over? What are the values of [itex]\textbf{B}[/itex] and [itex]\Phi_M[/itex] along that surface?
 
  • #3
He told us the problem was given to us intentionally very general, so none is specified. Could I argue that for an enclosed region in space with no enclosed magnetization, the integral is zero because all the flux in goes out again (kind of like the EM flux arguement)?
 
  • #4
Old Guy said:
He told us the problem was given to us intentionally very general, so none is specified. Could I argue that for an enclosed region in space with no enclosed magnetization, the integral is zero because all the flux in goes out again (kind of like the EM flux arguement)?

No, I don't think that works...

[tex]\oint\Phi_{M}\textbf{B}\cdot{d}\textbf{a}[/tex]

does not represent the magnetic flux.

What is the exact wording on the original question? (If it's a problem from Jackson, just state the problem number)
 

1. What does the integral of B dot H equal to zero mean?

The integral of B dot H equal to zero means that the total magnetic field strength (B) multiplied by the magnetic field intensity (H) is equal to zero when integrated over a three-dimensional space. This indicates that the total magnetic energy within the given space is constant or remains unchanged.

2. What is the significance of proving that the integral of B dot H is equal to zero?

Proving that the integral of B dot H is equal to zero is significant in understanding the behavior and properties of magnetic fields. It also helps in verifying the accuracy of mathematical models and theories related to electromagnetism.

3. How is the integral of B dot H calculated?

The integral of B dot H is calculated by taking the dot product of the magnetic field vector (B) and the magnetic field intensity vector (H) at each point within the given space and then integrating over the entire volume using the appropriate mathematical methods.

4. Can the integral of B dot H ever be non-zero?

Yes, the integral of B dot H can be non-zero in certain cases, such as when there is a non-conservative magnetic field or when the integration is done over a space where the magnetic field is not uniform. In these cases, the integral of B dot H represents the change in magnetic energy within the given space.

5. How is the statement "the integral of B dot H is equal to zero" proven?

The statement "the integral of B dot H is equal to zero" can be proven using various mathematical techniques and principles, such as vector calculus, divergence theorem, and Stokes' theorem. These methods involve manipulating and simplifying the integral to show that it is equal to zero.

Similar threads

Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
4K
Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
7
Views
3K
  • Advanced Physics Homework Help
Replies
15
Views
2K
Replies
6
Views
952
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Electromagnetism
Replies
19
Views
2K
  • Advanced Physics Homework Help
Replies
6
Views
2K
  • Advanced Physics Homework Help
Replies
7
Views
1K
Back
Top