Which material will stop magnetic attraction?

[songoku]

Homework Statement

Please see below

Relevant Equations

None

The answer key is (a) but I don't understand why. Option (a), (b), (c) are all non - magnetic material and (d) is magnetic material. Why (a) can stop the attraction while others can't?

Thanks

 

[berkeman]

Can you post a link to the online question? Obviously any magnetic shielding effect would require a ferrous material.

 

[songoku]

Can you post a link to the online question? Obviously any magnetic shielding effect would require a ferrous material.

Sorry I got the question in form of printed paper so I don't have the link. I think the answer is (d) but I am not sure how the distribution (shape) of magnetic field inside the steel sheet would be. Is there any possibility some part of the magnetic field is redistributed by the steel sheet towards the steel ball so it would still be attracted?

Thanks

 

[kuruman]

I will rephrase the question.

Which of the four materials exhibits stronger diamagnetism? A superconducting sheet would work even better.

 

[Steve4Physics]

The answer key is (a) but I don't understand why. Option (a), (b), (c) are all non - magnetic material and (d) is magnetic material. Why (a) can stop the attraction while others can't?

IMO the answer-key is wrong and the correct answer is d - the steel sheet.

Steel* has a high magnetic permeability. A large steel sheet will concentrate and redirect the field lines like this:

It’s worth noting that this wouldn’t apply with a narrow piece of steel. In that case, the local affect on the field would be more like this:

The steel would locally propagate the field in its original direction.

Diagrams from http://www.excelatphysics.com/magnetic-shielding.html

*Assuming this is not a non-magnetic variety of stainless steel!

 

[Gavran]

The answer key is (a) but I don't understand why. Option (a), (b), (c) are all non - magnetic material and (d) is magnetic material. Why (a) can stop the attraction while others can't?

Thanks

I think you are right, and the correct answer is d.
A copper shield can be better than a steel shield against a high-frequency magnetic field, but based on the picture from the original post, there is only a static magnetic field.