Finding Final Flux in a Flat Coil-Ring System

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Homework Help Overview

The problem involves a flat coil placed at the center of a larger ring, with the goal of determining the total charge circulating in the ring as the current in the coil increases. The context includes concepts from electromagnetism, specifically magnetic flux and induced charge.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between magnetic flux and current, with attempts to express flux in terms of magnetic field and area. Questions arise regarding the geometry of the coil and its relevance to the problem.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem and questioning the adequacy of the given information. Some guidance has been offered regarding the calculation of magnetic flux, but no consensus has been reached on the implications of the missing radius of the coil.

Contextual Notes

There is uncertainty regarding the radius of the coil, which is not provided in the problem statement, leading to questions about its impact on the solution. Participants note that the area of the coil is given, but the relevance of the ring's radius is debated.

zorro
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Homework Statement



A flat coil of area A and n turns is placed at the centre of a ring of radius r(r2>>A) and resistance R. The two are coplanar. When current in the coil increases from 0 to i, the total charge circulating in the ring is?

The Attempt at a Solution



dQ=dΦ/R

Initial flux = 0
How do I find out the final flux through the ring?
 
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To find flux, find B and the effective area: [tex]\Phi = \oint \vec{B}d\vec{S}[/tex] :smile:
To find B, find current of the B source and its geometry: B~i :smile:
 
B at the centre of the coil is μnI/2a, where a is the radius of the coil.
Flux through the bigger ring is B*A.
The problem I am facing is that the radius of the ring is given, not that of the coil.

Edit: Is something wrong with the question?
 
Last edited:
So what? :biggrin:
 
lol...so what?
The final answer contains 'a' (not given in the question) not 'r'.
 
We have the area of the coil A, right?
r is redundant here I guess.
 
Even your 'guesses' are always 100% correct :smile:
Thanks!
 

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