Stripped-Down Motor In this activity, you’ll make an electric motor—a simple version of the electric motors found in toys, tools, and appliances everywhere. What Do I Need? • aluminum foil • paper clips (larger is better) • paper, plastic, or foam cup • masking tape • magnets (two or more, available at Radio Shack) • scissors • copper wire (bare or coated) • sandpaper • battery (D or C cell) • permanent marker (any color is fine) What Do I Do? Building the Stand other piece of foil and paper clip. 1. Tear off two narrow sheets of aluminum foil. These will connect 4. Place the paper cup upside-down the motor to the battery. on the table. Tape the foil-covered 2. Take a paper clip and bend the outside wire down, so that you have a loop with post. Repeat with another paper clip. 3. Wrap one end of the aluminum foil around the long post of the paper clip. Make sure there is good contact between the paper clip and the foil. Repeat with the www.exploratorium.edu/afterschool Exploratorium end of one paper clip to the top of Turn over the cup and drop the inverted paper cup. Tape the another magnet inside. The two other paper clip to the opposite magnets will stick together. side. 6. Put the cup back on the table 5. Place a magnet on the top of the upside-down. This is the base for cup, between the paper clips. your motor. Making the Coil wire with two bare ends sticking 1. Cut a length of about 2 feet (60 out from either side. cm) of copper wire. 5. Balance the coil between two 2. If the wire is coated, use the fingers and see if it spins easily. If sandpaper to scrape away about it is too off-balanced to spin an inch (2 cm) of the coating on smoothly, adjust it. either end of the wire. 6. Use the permanent marker to 3. Wrap the coated part of the wire mark one side of one end of bare around the battery to make a coil, wire. then remove the coil from the battery. 7. Rest the ends of the coil in the cradles formed by the two paper clips. 8. Adjust the height of the paper clips so that when the coil spins, it just clears the top magnet. 9. Connect the battery by pressing the two free ends of the aluminum 4. Poke the bare ends of the wire foil pieces against either end of into and around the coil several the battery. times to fix the coil in place. You 10. Give the coil a spin to start the should now have a loop of coated motor turning. www.exploratorium.edu/afterschool Exploratorium Note: If the coil won’t spin, check that the coil is well balanced, that the coating has been thoroughly scraped off the ends, that the one end has been marked on one side with the marker, and that the coil and magnet are close but not touching. Keep adjusting if necessary—it will work. What’s Going On? Electricity flows through the coil of wire and creates an electromagnet. One face of the coil becomes a north pole, the other a south pole. The permanent magnet below attracts its opposite pole on the coil and repels its like pole, causing the coil to spin. Another way to explain this is the motor effect: when electricity moves through a wire in a magnetic field, a force results that moves the wire. Why is it important to color half of one projecting wire with a marker? By marking half of one end, you insulate the wire and prevent electricity from flowing through it for half of each spin. This turns off the electromagnet for that half spin, allowing momentum to carry it through to the next cycle. If you allowed the electricity to flow continually, one pole of the electromagnetic coil would just be continually attracted to the permanent magnet, and the coil wouldn’t spin. www.exploratorium.edu/afterschool Exploratorium.