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Himanshu posted an Question

July 04, 2020 • 06:11 am

30 points

IIT JAM
Physics (PH)

Flux numerical

Explain me the highlighted part of the solution. How Value of ds comes & why they are doing double integration & how they select limits.

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Dhairya sharma

see attached
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dear....we have to add one extra term which if cos thitha due to direction convection and from geometry
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it will help u
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Chandra prakash

see attached file it's very helpful for you dear and go through the concept of spherical coordinates stystm....best regards
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see attached file
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see
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Dhairya sharma

dear....we have to add one extra term which if cos thitha due to direction convection and from geometry
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Ghost.

In your derivation you didn't mention the cos(theta) explicitly, but you consider it Directly in area element, that's what create all fuss. Remember flux has to be normal to the surface.
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Ghost.

Important - here i am attaching derivation of area element which trouble you. in last step i multiple cos(theta) because i take dot product between E.F and area element. Hope it helps.
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Ghost. Best Answer

Your first doubt is about infinitesimal area element, i.e is area element in terms of d(theta) and d(phi). i will attach picture about mathematical derivation of it . 2nd doubt is about integration limit, you have to understand it theta can't go from 0 to pi as usual it has upper limit restricted by area of disk. ( theta max) i hope you understand flux is no. of field lines passing normally per unit area per unit time through surface. you uploaded photo doesn't mention the dot product between area element and E.F . i am attaching another solution for it. hope it hepls.
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