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Stop when the straw is halfway through the hole. If the straw falls through because the hole is too big, use glue to hold it in place. Make the hook about 1 inch (2.5cm) long. If the hook touches the sides of the jar when the lid is on, it's too big.If there isn't enough wire hanging down through the straw to make a hook with, unwind some of the spiraled end of the wire so you can push more down through the straw. Slide the holes you punched in the aluminum pieces onto the hook. When you're done, both pieces should be hanging right next to each other on the hook. To test your electroscope, get an inflated balloon or a rubber-soled shoe and quickly rub it back and forth between your hands. Then, hold the object next to the copper spiral at the top of your electroscope. You should see the 2 pieces of aluminum foil move away from each other. The more charged an object is, the more the pieces of foil will move away from each other. Try testing out different objects to see which ones have strong charges and which ones don't!
Slide the straw through the hole in the jar lid. Bend the straight end of the wire to make a hook. Hang the pieces of aluminum foil from the hook end of the wire. Screw the lid on the jar and test out your electroscope.