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Hello everybody! Although this may sound like a homework problem, I can assure you that it isn't. To prove it, I will give you the answer: 40pi.

So.. I'm self-studying some electrodynamics. I'm using the third edition of Griffiths, and I have a quick question. For those who own the book and want to follow along, I am doing problem 1.42 on page 45.

Here is the problem as given to me:

http://img151.imageshack.us/img151/1237/85625524.png [Broken]

Here is my solution:

http://img547.imageshack.us/img547/404/77923328.png [Broken]

Although I get the right answer, I'm questioning my method a little bit. I know that the flux integrals across the rectangles in the xz and yz planes are 0, and my method gives that they are 0. However, I know that Griffiths often finds ds in cylindrical coordinates in a different way, and I'm wondering if my way is mathematically valid. Thank you all very much!

EDIT: I justified it to myself, and I now see how my surface element and Griffiths' are the same. The s-dependence in ds actually falls out (which, for some reason, I didn't notice before), and you are left with just phi-hat. I apologize for making a topic before thinking about it for long enough. However, if you have anything about the problem/life to contribute, feel free! :) If I knew how to close this, I would.

So.. I'm self-studying some electrodynamics. I'm using the third edition of Griffiths, and I have a quick question. For those who own the book and want to follow along, I am doing problem 1.42 on page 45.

Here is the problem as given to me:

http://img151.imageshack.us/img151/1237/85625524.png [Broken]

Here is my solution:

http://img547.imageshack.us/img547/404/77923328.png [Broken]

Although I get the right answer, I'm questioning my method a little bit. I know that the flux integrals across the rectangles in the xz and yz planes are 0, and my method gives that they are 0. However, I know that Griffiths often finds ds in cylindrical coordinates in a different way, and I'm wondering if my way is mathematically valid. Thank you all very much!

EDIT: I justified it to myself, and I now see how my surface element and Griffiths' are the same. The s-dependence in ds actually falls out (which, for some reason, I didn't notice before), and you are left with just phi-hat. I apologize for making a topic before thinking about it for long enough. However, if you have anything about the problem/life to contribute, feel free! :) If I knew how to close this, I would.

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