Do multiple permanent magnets aggregated together approach the same strength as a single magnet of the same size? Here's an applied physics question. ;) If I buy some cube or sphere magnets like these, can I aggregate them together to create a stronger magnet (almost as strong as a single magnet)?
 A: If you stack the magnets the way they want to stack you will have no change in strength.
But if you can push the magnets together like this 
-----→        》NS《》SN《》NS《        ←--------------
Then you can increase the field and strength.
but the field extends  far in one direction only.
Mythbusters had a show about using magnets as breaks.
Thats where I learned about this.
So you need a
                           NSSNNS or a SNNSSN alignment .
hope this helps someone out with a project or two.
A: It seems stacking smaller and smaller magnets on top of each other generates the affect you are looking for. Check out what SuperMagnetMan did with "pyramid" magnets.
A: Although the combined strength will be larger, it will not be exactly the same as the strength of single large magnet. This is because the magnets lower down in the stack are being shielded slightly by the magnets above and below them.
A: To expand on Omar's Answer: KJMagnetics has an FAQ that answers this question: http://www.kjmagnetics.com/FAQ.asp#stack.
If you wander round the KJMagnetics site, they give a lot of technical information (I bought some magnets off them 2-3 years ago).
Their FAQ answer describes the situation for stacking flat magnets vertically on top of each other. Note that if you place multiple magnets next to each other horizontally, instead of in a vertical stack, they will still act in the same way as a larger magnet having the same area. However, in the horizontal case, the magnets will repel each other because like poles are next to each other (N next to N, S next to S). So you would have to impose an equal and opposite force to keep them together. That's not easy when the magnets get large.
