What happens to the current in a loop when a magnet approaches

[Selene0001]

Homework Statement

There is a magnet that approaches the loop as in the figure. There is already a counterclockwise current in the loop.

What happens to the current in the loop? Is my reasoning correct?

Homework Equations

The Attempt at a Solution

Since the flux is increasing in the loop, the induced current will oppose the change and be in the opposite direction. The direction of the field will be into the page. The loop already has a current in the opposite direction with a field pointing out of the page. This reduces the overall field and the current will decrease.

 

[gneill]

The diagram implies that the magnet is in the plane of the loop. How will its presence change the flux through the loop?

 

[Selene0001]

Aren't the field lines closer together towards the magnet? Then there would be more of them if the magnet gets closer to the loop?

 

[gneill]

Aren't the field lines closer together towards the magnet? Then there would be more of them if the magnet gets closer to the loop?

More of them doing what? Wouldn't the field lines be equally distributed going "upwards" and "downwards" through the loop? I think that the net result will be zero .

 

[Selene0001]

If it moves closer, won't the concentration of them in the loop be greater?

 

[gneill]

The only field lines that count towards flux though the loop are those that pass through the plane of the loop. Lines that cross the loop from edge to edge make no contribution, no matter how dense they might be.

 

[Selene0001]

That makes sense. Thanks!