Calculating Change in Flux: A Challenge!

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Homework Help Overview

The problem involves a flexible circular conducting loop in a magnetic field, where the loop is stretched to reduce its area to essentially zero. The task is to calculate the change in magnetic flux through the loop during this process.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between the change in area and time, with some suggesting a simple estimate of flux change using initial and final areas. Others clarify that the change in flux is independent of time and should be calculated using the difference between final and initial magnetic flux values.

Discussion Status

There is an ongoing exploration of different equations and approaches to calculate the change in flux. Some participants have provided differing results based on their calculations, leading to questions about which approach is correct. The discussion remains open without a clear consensus on the correct method.

Contextual Notes

Participants note the lack of specific information regarding how the area changes over time, which may affect the calculations. There is also mention of the potential confusion caused by referencing Faraday's law in the context of the problem.

jimbkob
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Homework Statement



A flexible, circular conducting loop of radius 0.15m and resistance 4 ohms lies in a uniform magnetic field of .25 T. the loop is pulled on opposite sides by equal forces and stretched until its enclosed area is essentially zero m^2. it takes .30s to close the loop. what is the change in flux? :confused:




Homework Equations



I know this problem involves Faraday's law but I'm having trouble finding the answer. Can someone please help me?


The Attempt at a Solution

 
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since there are no details on the change in area with respect to time (i.e. you don't know exactly how the area changes as it bends from the 2 forces) it seems like a simple estimate using final - initial

B\frac{A_F-A_i}{t_F-t_i}
 
The change in flux doesn't depend on time. It's just the final BA minus the initial BA.
 
Thanks for the quick response!

I'm not say either of you guys are wrong but I tried both equations and I got two different answers.

The first equation got me .01767 but when i plug this into Faraday's equation I get -0.0589 volts

The second equation got me -0.0589 Wb.

Which one is correct?
 
jimbkob said:
Thanks for the quick response!

I'm not say either of you guys are wrong but I tried both equations and I got two different answers.

The first equation got me .01767 but when i plug this into Faraday's equation I get -0.0589 volts

The second equation got me -0.0589 Wb.

Which one is correct?

i accidentally told you how to find the change in flux with respect to time (I saw you mention faraday's law and it set me on that track)

If the problem is only asking for the change in flux, do what ideasrule said:
B(A_f - A_i)

sorry about setting you off on the wrong track.
 
haha no it's ok no big deal. Thanks again!
 

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