Question of a problem on Poynting vector

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Discussion Overview

The discussion revolves around a problem related to the Poynting vector, specifically focusing on the participant's difficulty in reconciling their solution with that provided in a textbook. The scope includes problem-solving and technical reasoning regarding electromagnetic fields represented by phasors.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • A participant expresses frustration over their inability to match the textbook solution for a problem involving the Poynting vector, indicating they have reviewed their work multiple times.
  • Several participants note that the attachment containing the problem and solution is pending approval, suggesting alternative methods for sharing the document.
  • One participant questions the correctness of the expressions for the real parts of the electric field \(\mathbf{E}(R,\theta,t)\) and magnetic field \(\mathbf{H}(R,\theta,t)\), pointing out the need to account for the imaginary unit 'j' in the phasor representation.
  • The same participant acknowledges their oversight regarding the transformation of the phasor expression, specifically how 'j' affects the sine and cosine components.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the original expressions for \(\mathbf{E}\) and \(\mathbf{H}\), as there is a challenge to the participant's initial work without a definitive resolution to the problem presented.

Contextual Notes

The discussion highlights the dependency on the approval of attachments for sharing information, which may hinder the flow of the conversation. Additionally, there is an unresolved aspect regarding the mathematical steps involved in transforming the phasor expressions.

yungman
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I have been working on this problem and I cannot get the solution as shown in the book. I scan the question and solution of the book and my work. It is too difficult for me to type it in, please open the attach scanned pdf file. THe top part is the copy of the book, the lower part is my work. You can see the solution on my part does not agree with the book and I check over my work many times already. Please tell me what did I do wrong
Thanks
 

Attachments

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We can't see your attachment until it is approved by admin. It would be quicker if you uploaded your pdf to imageshack.us and then posted a link to it.
 
gabbagabbahey said:
We can't see your attachment until it is approved by admin. It would be quicker if you uploaded your pdf to imageshack.us and then posted a link to it.

It can be opened now.
Thanks
 
yungman said:
It can be opened now.
Thanks

Not by me it can't. It still says that it is pending approval.
 
gabbagabbahey said:
Not by me it can't. It still says that it is pending approval.

I just opened already! I wonder why!
 
You can open it before it has been approved since you are the one that attached it. Everyone else has to wait 'til its approved.

Again, you can save a lot of time by uploading it to a free imagehosting site and then just posting a link to it.
 
I don't think your expression for the real part of [tex]\mathbf{E}(R,\theta,t)[/tex] and [tex]\mathbf{H}(R,\theta,t)[/tex] are correct. Remember that the original phasor expression for E and H has 'j' inside, meaning that you have to multiply throughout by j, so that makes the formerly imaginary part real and the formerly real part imaginary.
 
Defennder said:
I don't think your expression for the real part of [tex]\mathbf{E}(R,\theta,t)[/tex] and [tex]\mathbf{H}(R,\theta,t)[/tex] are correct. Remember that the original phasor expression for E and H has 'j' inside, meaning that you have to multiply throughout by j, so that makes the formerly imaginary part real and the formerly real part imaginary.

Thanks again. It is so obvious that I just miss it all together. "j" translate to e to the power j(pi/2) which change the cos() to -sin().

Thanks again.
 

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