Magentic induction and shielding

[serverxeon]

This happens when the ferro-magnetic material is placed near to the magnet. (call this induced magnetism)

BUT

if the bar shape ferro-magnetic material's length is compressed into as thin as a sheet of iron,

Electromagnetic shielding occurs.

--------------------

In the first situation, an iron pin will be attracted by the induced iron, but in the second situation, the iron pin will not be attracted.

I do not understand why will there be two occcurance, and how to classify any situation to know which will occur.

 

[HallsofIvy]

What "pin" are you talking about? In the first case you have a bar of iron that is attracted to the magnet. In the second you flatten the iron into a sheet which will also be attracted to the magnet. I see no "pin" in either case.

 

[serverxeon]

the pin is not in the picture
imagine a pin approach the iron bar, or sheet in both cases, from the right.

From what i was told, the magnetic field will flow through the iron bar, therefore magnetising it. (so the pin will be attracted to the iron bar)

But, in the case of a the iron sheet, the magnetic field is diverted(shielding), and anything belhind will not experience magnetism from the magnet. (the pin does not feels any attraction)

what difference is there between a sheet and a bar magnet? isn't it just the 'length' of that piece of iron? why are there 2 different results?