The strongest magnets known are electromagnets. Sometimes they will even stick together on either side of your hand, and they are great for science experiments. If you like making your own science tools and have been wanting a strong magnet, you can make your own electromagnet. Of course, you should always work with a qualified adult when using batteries and other power sources.
Wrap your 4-gauge copper wire tightly around your 10-inch-long iron nail. The closer and tighter the wrap, the stronger your magnet will be.
Snip the ends off the wire. When your nail is wrapped, leave about 6 inches remaining on the ends, and cut them with a wire cutter. It doesn't have to be exact, as these ends are going to be inserted into the clamps.
Unscrew the end of the clamps. Use the flat-bladed screwdriver.
Attach the wires to the clamps. Insert the ends of your wires, one wire into each clamp. Then screw down the screws to make a tight fit.
Attach the clamps to your battery. There may be an initial spark, but that is okay. Once the clamps have been attached to the battery, the coil around the nail will become electromagnetized. It will be powerful enough to attract fairly large or heavy pieces of steel, such as large bolts or even railroad ties, unlike most smaller magnets, which are limited to items like paperclips. You will have to experiment to see exactly how large an object you can attract and how the length of time the nail is clamped to the battery affects the degree of magnetization. You can leave the clamps in place for several minutes if you like, but just a few seconds will magnetize the nail.
Read more: How to Make Strong Magnets | eHow.com http://www.ehow.com/how_5004980_make-strong-magnets.html#ixzz2HCec70V8