Best Science Toys - Learning about magneticism
Fun with magnets
Cool magnet experiments
Magnets and iron filings experiments
Fun with FerroFluid!
Seeing Science - Playing with magnets
The best way to learn is by hands on experimentation and with magnets this can be a lot of fun for kids.
The force of magnetism is invisible but that doesn't mean it can't be observed. Simple experiments such as attracting paper clips to small magnets show the force of magnetism.
The poles (north and south) of magnets can be seen if you put the poles of two magnets together, they will either pull together or push apart. They will pull (attract) each other if the poles are different. They will push (repel) each other if the poles are the same. Opposites attract!
Iron filings make for cool experiments with magnets. Put some iron filings on a sheet of paper and place a magnet underneath. The filings will arrange themselves according to the magnetic field surrounding the magnet.
Another cool way to experiment with magnets is to use Ferrofluid. Ferrofluid (compound of Latin ferrum, meaning iron, and fluid) is a liquid which becomes strongly magnetized in the presence of a magnetic field. Ferrofluids are composed of nanoscale particles (diameter usually 10 nanometers or less) of magnetite, hematite or some other compound containing iron. This is small enough for thermal agitation to disperse them evenly within a carrier fluid, and for them to contribute to the overall magnetic response of the fluid. See the video below for some cool shapes the magnetic particles in the fluid make when exposed to magnetic field.
You can also use magnets to check metals to see if they have iron in them. Give kids a magnet and several types of metal (coins, office supplies, "tin" cans) to test for iron. You can also magnetize items such as a screwdriver by rubbing a magnet across the screwdriver to arrange the molecules. Test your newly magnetize screwdriver with some screws.
You can also similarly magnetize a needle, place it on a cork and float it in a bowl of water to make a crude but useable compass.
Warning - When I was a kid someone gave me a big cow magnet. Cows eat just about anything including bottle caps and pieces of metal wire they might find while grazing. Cow magnets are put in the cows stomachs to attract the metal together so it doesn't pass through and hurt the cow further. So anyway, I have this big magnet and I say to my Mom "lookie, lookie what I can do!". I was waving the magnet around in front of the TV screen and all the color was attracted the the magnet. I basically degaussed the TV and broke it. I believe this doesn't happen with modern TVs and monitors but strong magnets can wreck havoc with your electronics especially storage devices such as hard drives.
Other warnings - keep small magnets away from small children. If two magnets are swallowed they can attract each other in the intestine and cause blockages that can lead to death! Also be careful with Ferrofluid. It can stain clothing.