Faraday's Law and a metal loop

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The discussion centers on the effects of a cut in a metal loop on induced electromotive force (emf) and current when subjected to rotation in a magnetic field. It is concluded that the maximum induced emf remains the same for both the uncut and cut loops, as Faraday's Law indicates that emf is related to the rate of change of magnetic flux, which is unchanged. However, the maximum induced current in the uncut loop is significantly higher than in the cut loop, due to the continuous path for current flow in the uncut loop versus the high resistance created by the gap in the cut loop. The cut loop behaves like a circuit with a very high resistance, resulting in minimal current. Thus, while the emf is equal, the current differs greatly due to the loop's integrity.
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Homework Statement


A metal loop is attached to an axle with a handle as shown. The north pole of a magnet is placed blow the loop and handle turned so that the looks rotates counterclockwise at a constant angular speed.

Suppose the loop (the one above) were replaced by a second loop that is identical to the first except for a small cut in it. The loop is rotated as before.
1. How does the maximum induced emf in the uncut loop compare to the maximum induced emf in the cut loop?
2. How does the maximum induced current in the uncut loop compare to the maximum induced current in the cut loop?


Homework Equations


This question is conceptual


The Attempt at a Solution


Well, for #2 I think that the maximum induced current in the cut loop will be smaller than in the uncut loop, because in the uncut loop the current continuously moves around the loop. This does not happen in the cut loop.
But as for #1, I don't really know how to relate current to emf.

Any suggestions on what to do?
 
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robera1 said:

Homework Statement


A metal loop is attached to an axle with a handle as shown. The north pole of a magnet is placed blow the loop and handle turned so that the looks rotates counterclockwise at a constant angular speed.

Suppose the loop (the one above) were replaced by a second loop that is identical to the first except for a small cut in it. The loop is rotated as before.
1. How does the maximum induced emf in the uncut loop compare to the maximum induced emf in the cut loop?
2. How does the maximum induced current in the uncut loop compare to the maximum induced current in the cut loop?

Homework Equations


This question is conceptual

The Attempt at a Solution


Well, for #2 I think that the maximum induced current in the cut loop will be smaller than in the uncut loop, because in the uncut loop the current continuously moves around the loop. This does not happen in the cut loop.
But as for #1, I don't really know how to relate current to emf.

Any suggestions on what to do?

Faraday's Law says that the line integral of electric field (i.e. voltage potential) around a loop is equal to the negative rate of change of flux penetrating the area bounded by the loop (EMF due to flux change). The voltage potential will be the resistance of the loop times the current in the loop. However, the EMF due to flux change is the same in both cases. You correctly noted that the current is very small for the cut loop. The current in the uncut loop is very high since the conductor resistance is small. So basically, the EMF is the same in both cases and since EMF is equal to the potential, the current is low in once case (high resistance) and the current is high in the other case (low resistance). Basically, the cut wire acts like a perfect conductor with a very high resistance in the gap. So the potential in directly across the gap. The uncut wire has the potential drop is a distributed way across the whole wire.
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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