How does the size of an object dictate a magnet's effect upon it?

[Patch]

I used a bunch of little finishing nails to attach the backing board to a set of shelves I bought from Ikea. The last time I did this I screwed it up and had to take it off, and ended up pulling the nails through the board as I couldn’t get a grip on them with a hammer.

I was wondering about using a really strong magnet to yank the nails out, but then I started wondering if a really strong magnet would exert enough force on a little nail to pull it out of wood. It seems to me that the size of the attracted object will dictate how the magnetic field can act upon it, but what are the limits?

[cmyk]

Not really the size, per se, but how strong a magnetic field a magnet can produce.

Some neodymium/rare earth magnets are dangerously powerful for their size:

@Wikipedia

Hazards

The greater force exerted by rare earth magnets creates hazards that are not seen with other types of magnet. Neodymium magnets larger than a few cubic centimeters are strong enough to cause injuries to body parts pinched between two magnets, or a magnet and a metal surface, even causing broken bones.

Magnets allowed to get too near each other can strike each other with enough force to chip and shatter the brittle material, and the flying chips can cause injuries. There have even been cases where young children who have swallowed several magnets have had a fold of the digestive tract pinched between the magnets, causing injury or death. The stronger magnetic fields can be hazardous to mechanical and electronic devices, as they can erase magnetic media such as floppy disks and credit cards, and magnetize watches and other clockwork mechanisms and the shadow masks of CRT type monitors at a significant distance.

Still, good luck trying to pull a nail out of a board with a magnet. To do that, you might need something like a powerful electromagnet, like from a junkyard for picking up cars, or put it in an MRI.

ETA: I see you got it from IKEA. Have you tried a typical fridge magnet.

[Michael63129]

The size of an object does determine how strong of a pull the magnet has; you can easily remove a nail stuck head-first to a neodymium hard drive magnet, but put the same magnet on a block of metal and good luck trying to pull it off without sliding it off the edge.

[dexter]

Just a tech, not an Eng., but I believe that something called “flux saturation” is what limits the ability of any magnet to attach itself to another object. I.E., if a really strong magnet (lots of flux lines) encounters a small object, those strong lines can still only act on the area that the object interrupts.

[Patch]

@dexter

Just a tech, not an Eng., but I believe that something called “flux saturation” is what limits the ability of any magnet to attach itself to another object. I.E., if a really strong magnet (lots of flux lines) encounters a small object, those strong lines can still only act on the area that the object interrupts.

That’s the concept I was thinking of. When I tried looking up magnets and sizes, all I got was stuff about varying the magnet size, not the object. Thanks.