Today we played with electromagnets. I had already set up a snap circuits demo with a solenoid and showed that when the current was turned on the iron core was sucked into the solenoid. Then I had the students make their own solenoid with wire, a large iron nail and various batteries. I challenged them to make a better solenoid – who can pick up the most paper clips with their electromagnet. We talked about how more turns would make it stronger or more current (more batteries). I also have a Texas Instrument sensor that connects to my iPad via bluetooth and it can measure the magnetic field directly. The largest reading we got was around 0.9mT.
The students also made little coils that will keep spinning when placed over a magent. These are a lot of fun and the students always enjoy making these. Its helps to have strong magnets, but you can make it work with most regular magnets and a bit of magnet wire.
One student made a large coil and hooked it up to an ammeter, but NO BATTERIES. Obviously no current was going through the coil, but when you move a magnet in and out of the coil it induces a current in the circuit. We were able to get close to 1mA by dropping neodynium magnets through the coil.
Speaking of neodynium magnets… I want to do this demo so bad.