Question about the Magnetic Flux equation in Integral form

Click For Summary

Homework Help Overview

The discussion revolves around the integral form of the magnetic flux equation, specifically focusing on the role of the dot product in the integrand and the implications of varying angles across a surface.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the explicit expression for the integral form of magnetic flux and question the presence of the dot product in the integrand. There is a focus on understanding how the cosine term is represented and its implications for integration across a surface.

Discussion Status

Some participants have provided guidance on the correct expression for magnetic flux and discussed the nuances of the dot product in relation to varying angles. There seems to be an ongoing exploration of the implications of these concepts without a clear consensus.

Contextual Notes

Participants note that the cosine term is not constant across the surface, which complicates the integration process. There is also mention of the compactness of the notation used in the equation, suggesting a deeper complexity beneath the surface.

Einstein44
Messages
125
Reaction score
31
Homework Statement
I was a bit confused with all the formulas for Flux, so here's my question...
I know that for a uniform B field flux is defined as ##\phi =BAcos\Theta ##, however when looking at the integral form I never saw it written with ##cos\Theta##... Is there a reason? Could it still be written with a cos at the end??
Relevant Equations
.
.
 
Physics news on Phys.org
Can you give us the explicit expression for the integral form? Does the integrand have a dot product of vectors?
 
  • Like
Likes   Reactions: vanhees71 and Delta2
Yes, @TSny implies that the ##\cos\theta## term is hidden inside the dot product of the vectors. But is not a constant term like it is in the case of a uniform magnetic field and a plane surface, it varies as we move from point to point on the surface, which is what makes the integration difficult.
 
TSny said:
Can you give us the explicit expression for the integral form? Does the integrand have a dot product of vectors?
Yes, it is ##\phi =\iint_{S}B\cdot dS##
 
Delta2 said:
Yes, @TSny implies that the ##\cos\theta## term is hidden inside the dot product of the vectors. But is not a constant term like it is in the case of a uniform magnetic field and a plane surface, it varies as we move from point to point on the surface, which is what makes the integration difficult.
So you are saying that it is implied due to the dot product, but just not shown in the equation. I am not sure I fully understand what is going on, but I get what you are saying.
 
Einstein44 said:
So you are saying that it is implied due to the dot product, but just not shown in the equation. I am not sure I fully understand what is going on, but I get what you are saying.
Yes well you wrote correctly the formula at post #4, but the whole point there is that ##B\cdot dS## is a very cute and compact formalism that hides a mini can of worms underneath: If you want to exactly write its equal expression using cosine of angle its a kind of trouble.
 
  • Like
Likes   Reactions: Einstein44
Einstein44 said:
So you are saying that it is implied due to the dot product, but just not shown in the equation.
Yes. Note that for a uniform B field, you can write the flux in terms of a dot product as ##\Phi = B S \cos \theta = \vec B \cdot \vec S## where in the last expression the ##\cos \theta## is "hidden" in the dot product. You just want to make sure that you understand the meaning of an area vector.
 
  • Like
Likes   Reactions: Einstein44
TSny said:
Yes. Note that for a uniform B field, you can write the flux in terms of a dot product as ##\Phi = B S \cos \theta = \vec B \cdot \vec S## where in the last expression the ##\cos \theta## is "hidden" in the dot product. You just want to make sure that you understand the meaning of an area vector.
Got it, thanks!
 
  • Like
Likes   Reactions: berkeman

Similar threads

  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
25
Views
3K
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
7
Views
2K