Magnetic Flux & Current in a Dropped Magnet & Wire Loop

AI Thread Summary
When a bar magnet is dropped above a wire loop, the induced current in the resistor is affected by the direction of the magnet's movement. As the south pole approaches the loop, the current flows counterclockwise, and it switches to clockwise once the magnet moves away. The current's direction is determined by Lenz's Law, which states that the induced current will oppose the change in magnetic flux. The confusion arises from understanding how the magnetic flux changes as the magnet approaches and then leaves the loop. Ultimately, the current is first counterclockwise and then becomes clockwise as the magnet passes through the loop.
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Homework Statement


A bar magnet is held above the center of a wire loop lying in the horizontal plane, as shown in the figure below. The south end of the magnet is toward the loop. After the magnet is dropped, what is true of the current in the resistor as viewed from above? (Select all that apply.)
20-mc-figure-11.gif

It is counterclockwise as the magnet falls toward the loop.
It is clockwise as the magnet falls toward the loop.
It is always clockwise.
It is clockwise after the magnet has moved through the loop and moves away from it.
It is first counterclockwise as the magnet approaches the loop and then clockwise after it has passed through the loop.

Homework Equations


Lenz's law and Faraday's Law

The Attempt at a Solution


This is my conceptual picture of what's going on.

Untitled.png

As the magnet is falling in the field lines are going N to S as always. So Just at the moment when the bottom of the South pole of the magnets hits the area inside the circle the field lines are coming toward us (as viewed from the top). As the magnet falls through and the N side is facing us, the field lines are again, coming toward us.
In both cases the current will be induced in such a way that the magnetic flux through the surface is constant. So it seems to me that it should flow clockwise in both cases. This is, however, incorrect. Where am I going wrong?
 
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The induced emf is proportional to the change in (i.e., time derivative of) the magnetic flux, not to the magnetic flux itself.
 
Yes, that is what my pictures are trying to illustrate.
 
So how is the flux changing when the magnet falls into the loop? How is it changing when it falls out of the loop?
 
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