Wednesday, December 24, 2008

Physics: Build a motor

This week the kids built motors. First they made a coil of wire which rested on 2 metal struts attached to a battery. When connected to the battery, the coil became an electromagnet. Then they placed a small round magnet near the battery that was connected to the electromagnet. The 2 magnets: the regular one and the electromagnet exerted magnetic pulls and pushes on each other so that the coil rocked back and forth. To make it spin, we had to get creative...the kids put white out on the tops of the wire where the coil made contact with the metal struts. Doing this broke the circuit half the time. What did this do? When the circuit was closed, the coil became magnetic, which gave it an initial push away from the other magnet. When the circuit was broken, it was the momentum of the coil itself that carried it through the second half of the spin. In a perfect world, the coil would continue spinning until the battery ran out, but alas, we don't live in a perfect world. Besides gravity and electromagnetic forces, the kids had to contend with another challenging force.... FRICTION. The need to reduce friction explains why this activity took an hour, and not 5 minutes, and why by the time they got home, the motor may have stopped working. I guess you could say the kids got a lesson in real-world engineering. A bit frustrating, but definitely builds character!

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