1. Magnetic field lines are visible with the filings
Magnetic Induction
When a magnetic material is put by a magnet, it can extend the range of the magnet.
It can also act like a magnet for a little while afterward.
Both of these are caused by induction, which is where a material has a magnetic field generated inside it.
Imagine a nail is made of little magnets pointed everywhere. An outside magnet makes them line up.
The magnetic field is carried through the nail to hold the little nails or paper clips.
Magnetic field lines are visible with the filings