Explaining the Context of $\nabla\times A=0$ with a Uniform Y-Component of A

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In summary, the statement "Then the x- and z-components of the curl give you z- and x-independence of Hy respectively." means that the assumption of the curl of H being zero leads to the conclusion that the y-component of H is independent of both x and z, and thus is uniform.
  • #1
saravanan13
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I came across in a journal that for a [tex]\nabla[/tex][tex]\times[/tex] A=0 where A is vector, if y-component of that A is uniform then author claims that y-component of curl of a A is zero?
Can anyone explain the above context?
 
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  • #2
Are you sure that's what's being claimed? Because it isn't true; the y-component of the curl is independent of the y-component of the vector. Maybe there is something extra assumed about A? Can you link to the article or attach the relevant section?
 
  • #3
how to attach the pdf?
 
  • #4
see Eq. (7) and previous statement connecting to that...
 

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  • #5
The vanishing of the curl is what is assumed here (it's Ampere's law without currents). Then [itex]\partial_z H_x =\partial_x H_z[/itex] is just taking the y-component of the curl. The uniformity of the y-component of H is a separate conclusion, and comes from the assumption that nothing depends on y ("the wave is not modulated transversely"). Then the x- and z-components of the curl give you z- and x-independence of Hy respectively.

Hope that helps.
 
  • #6
Dear henry_m

Please clearly elucidate this statement "Then the x- and z-components of the curl give you z- and x-independence of Hy respectively."
 
  • #7
saravanan13 said:
Please clearly elucidate this statement "Then the x- and z-components of the curl give you z- and x-independence of Hy respectively."

Yeah sure, sorry that wasn't very clear.

We're assuming the curl of H vanishes from the physics. The x-component of this says that [itex]\partial_y H_z=\partial_z H_y[/itex]. But H is y-independent by assumption, so [itex]\partial_y H_z=0[/itex], and hence [itex]\partial_z H_y[/itex] is zero. This means that [itex]H_y[/itex] is independent of z.

If you do the same for the z-component of the curl, you find that [itex]H_y[/itex] is independent of x.

Finally, we're assuming H is independent of y. So [itex]H_y[/itex] is independent of x,y, and z, and hence uniform.
 

Related to Explaining the Context of $\nabla\times A=0$ with a Uniform Y-Component of A

1. What is the meaning of the equation $\nabla\times A=0$?

The equation $\nabla\times A=0$ represents the curl of a vector field A, which is a measure of the rotation of the field. This equation specifically states that the curl of A is equal to 0, indicating that there is no rotation in the field.

2. How does a Uniform Y-Component of A affect the equation $\nabla\times A=0$?

A Uniform Y-Component of A means that the vector field has a constant magnitude and direction in the y-direction. This would result in a zero curl in the y-direction, as there is no change in the field's rotation in that direction. Thus, the equation $\nabla\times A=0$ would still hold true.

3. What is the physical significance of $\nabla\times A=0$?

The physical significance of $\nabla\times A=0$ is that it represents a vector field that is irrotational, meaning there is no rotation or circular motion present in the field. This could be seen in a fluid flow, where there is no swirling motion or vortices present.

4. How is $\nabla\times A=0$ related to the concept of divergence?

The equation $\nabla\times A=0$ is related to the concept of divergence through the fundamental theorem of vector calculus. This theorem states that for a vector field A, if the curl of A is equal to 0, then the divergence of A is also equal to 0. In other words, an irrotational field also has zero divergence.

5. Can $\nabla\times A=0$ be applied to any vector field?

No, the equation $\nabla\times A=0$ can only be applied to certain vector fields, specifically those that are irrotational. This means that there is no circular motion or rotation present in the field. Vector fields that do have rotation would not satisfy this equation.

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