Calculating Induced EMF in a Coil with Uniform Magnetic Field

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Discussion Overview

The discussion revolves around a homework problem involving the calculation of induced electromotive force (EMF) in a coil made from a copper wire wrapped around a toilet paper roll, which is situated in a uniform magnetic field. The problem includes parameters such as the radius of the roll, the strength of the magnetic field, and the velocity at which the wire is unrolled.

Discussion Character

  • Homework-related, Technical explanation, Debate/contested

Main Points Raised

  • One participant seeks assistance in calculating the magnitude of the induced EMF based on the given parameters.
  • Another participant questions the association of speed with the unrolling process and requests the exact wording of the problem for clarity.
  • A different participant references Faraday's Law, suggesting that the induced EMF can be calculated using the formula involving the change in magnetic flux and the number of wire turns, indicating that the magnetic flux remains constant while the number of turns changes over time.
  • One participant expresses frustration regarding the posting of homework questions in an inappropriate forum, highlighting the existence of designated forums for such inquiries.

Areas of Agreement / Disagreement

There is no consensus on the approach to solving the problem, as participants express differing views on the appropriateness of the forum for homework questions and the clarity of the problem statement.

Contextual Notes

Participants have not fully clarified the assumptions regarding the relationship between the unrolling speed and the number of turns, nor have they resolved the specific details of the problem statement.

Sir_Pogo
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I have a homework problem where there is a long copper wire around a toilet paper roll that is placed in a uniform magnetic field. The axis of the roll is aligned with the field.
I am given the radius of the roll, strength of the field, and a velocity at which the wire is unrolled.
How do i calculate the magnitude of the EMF induced in the wire??
 
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How do you associate a speed to the unrolling?!? I don't understand.
Could you post the problem exactly as it it written please?

Btw - you posted in the wrong forum. Next time, please post in the appropriate sub-forum among those:

https://www.physicsforums.com/forumdisplay.php?f=152
 
Note that as it's said in Faraday's Law EMF is equal to d(N*magnetic_flux)/dt where N is a total amount of wire turns and magnetic_flux is per each one.

In your example your, magnetic_flux is const. and equal to BS=pi (r)^2 B. And only N changes in time. Try to think about dependence between N and time
 
What I have a lot of trouble understanding is... how do people with some sort of science education consistently misinterpret the sticky at the top of the forum that says 'Do not post your homework questions here.'? There are forums for that, but this is not one of them.
 

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