Home for the break! My brother asked me for help making a small electromagnet to bring into Boy Scouts for electricity merit badge. I of course jumped at the opportunity, and asked what kind of power source they are going to be using to drive said magnet. He tells me they will be using a single D battery. Thinking this is kind of small, I spent a few hours making the biggest electromagnet I could from a few things around the house I could find.
I ultimately settled on sawing an old golf club in half, stuffing a large bolt down the hollow inside, and then mounting the whole thing in a drill to facilitate easy winding of some low-gauge wire I found in our garage. To top it off, I powered the whole thing with an old computer power supply (5V at 25A I believe). The whole affair vaguely looks like some kind of torture device. The end result is a large electro magnet that can pick up very heavy weights and gets furiously hot and smells like burning plastic if left on for more than 5 minutes. Totally overkill for Boy Scouts, but totally awesome.