Which drawing represents an AC generator?

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Homework Help Overview

The discussion revolves around identifying which drawing represents an AC generator based on the setup involving a magnet and a coil. The original poster expresses confusion regarding the application of Fleming's right-hand rule in the context of the problem, particularly due to the motion of the magnet versus the coil.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants suggest drawing field lines to determine the orientation of the magnetic field relative to the coil. Questions arise about the meaning of "vertical rotation axis" and its implications for the problem. Some participants express uncertainty about the differences between the drawings and whether both could represent AC generators.

Discussion Status

The discussion is ongoing, with various interpretations being explored. Some participants have offered guidance on visualizing the magnetic field, while others are questioning the assumptions made in the problem statement. There is no explicit consensus on which drawing is correct, and the original poster is seeking further clarification.

Contextual Notes

Participants note that the problem specifies only one drawing as correct, which adds to the confusion. The implications of the "vertical rotation axis" are under scrutiny, with some suggesting it may clarify the situation.

Asmaa Mohammad
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Homework Statement


A magnet bar has been installed in the vertical rotation axis of a coil. Which of these drawings represents an AC generator?
tcOAm.jpg
2. Relevant rules

Fleming's right-hand rule.

The Attempt at a Solution



Fleming's right-hand rule assumes that the coil is in motion, but in the drawings the magnet is in motion, and that's what made me not able to know how to apply it correctly here. So could anyone give me some hints, please?
I think both (a) and (b) could be AC generators, but the problem statement says that only one is correct.
 
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Draw some field lines and see in which drawing(s) they could be in a direction perpendicular to the plane of the loop as the magnet rotates.
 
I don't see significant difference between (a) and (b).
Also, what is meant by vertical rotation axis?
 
kuruman said:
Draw some field lines and see in which drawing(s) they could be in a direction perpendicular to the plane of the loop as the magnet rotates.
Ok, here is it:
awpsP.jpg

And from that figure I would exclude drawing (c), but still (a) and (b) have a chance to be AC generators, right?
David Lewis said:
I don't see significant difference between (a) and (b).
Also, what is meant by vertical rotation axis?
I agree with you regarding (a) and (b), and also I don't understand what does it meen by saying "vertical rotation axis"!
 
The emf should be induced "along" the length of the coil. For this to happen,a component of magnetic field, "linear" velocity (instantaneous) 'v' of the magnet and length of the coil should be perpendicular to each other.
 
cnh1995 said:
The emf should be induced "along" the length of the coil. For this to happen,a component of magnetic field, "linear" velocity (instantaneous) 'v' of the magnet and length of the coil should be perpendicular to each other.
Ok, I think this happens in both (a) and (b), doesn't it?
 
Asmaa Mohammad said:
Ok, I think this happens in both (a) and (b), doesn't it?
Looks like it does.
So both a and b can be generators.
 
cnh1995 said:
Looks like it does.
So both a and b can be generators.
That's what confuses me actually, because the book says only one drawing is correct. Some people told me that may there be something regarding " the vertical rotation axis" which I don't understand, neither I understand what does it mean by "vertical rotation axis".
 
Asmaa Mohammad said:
That's what confuses me actually, because the book says only one drawing is correct. Some people told me that may there be something regarding " the vertical rotation axis" which I don't understand, neither I understand what does it mean by "vertical rotation axis".
If you just rotated b through 90 degrees CCW, you'll get a (I haven't checked the polarity).
So I think both the options are correct.
They have specified the axis of rotation and direction of rotation of the magnet in each case. So you need not think what vertical axis means here.

Does your book provide the answer?
 
  • #10
cnh1995 said:
Does your book provide the answer?
No, it doesn't. But in the problem statement it is clear that it considers only one drawing could be a generator, or that's what I think.
 

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