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Deepanshu posted an Question
May 15, 2020 • 00:37 am 30 points
  • IIT JAM
  • Physics (PH)

Line integral problem

In the 3rd problem, I am confused about the integration part. I am getting a factor of 2 after integration for phi. But in the answer it is not present.

1 Answer(s) Answer Now
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  • comment-profile-img>
    Ruby negi Best Answer

    yeah dear, you are right, this is done like this.. thanku... hope now everything is clear... sometimes we also do mistakes, I feel Happy that you did correct....

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    thanks mam.. this was actually where I was stuck

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    always welcome.. good luck...

  • comment-profile-img>
    Abhishek singh

    here is the solution. this is called gradient theorem

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    yeah thanks.. this part is clear but im still not getting how is it x^2y+ xz^3

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    what should be the answer according to you?

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    I am not getting what is bothering you?

  • comment-profile-img>
    Ruby negi

    hope now it is clear .

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    But if we integrate x^2 wrt y then we don't get the same answer. Nor do we get the same after integrating wrt z

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    if you integrate x^2 w.r.t y you get x^2*y and this is in the ans.

  • Deepanshu Chaudhary

    but my doubt is why can't we do it Directly??

  • comment-profile-img>
    Abhishek singh

    Rubii has attached a solution. And it is right, but there is a little correction. Phi is just phi, it has no components (you are absolutely right) . you can calculate phi from all three components of gradient (phi). Then arrange all factors from the three phi's without repetition. And you will get your actual phi.

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    But look at the answer below the question. It is 202 not 404. That is the 2 ka factor I have mentioned in my question

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    yes you are right answer should be 202. I am attaching a solution.

  • comment-profile-img>
    Ruby negi

    solution....

    cropped744579284.jpg
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    How is phi related to phi x, phi y and phi z?? Also, since phi is a scalar, how can it have x,y and z components?

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    I am attaching one more page. see it

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    ok

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